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SWP272710(5) (2)
HEC-RAS River:Springbrook Cr Reach:BRPS to 43rd Min. W.S. Elev Crit W S. E G Elev E.G Sky Vel Ch11 eft) (ft) (ft) {wft) (�S) BR 934.00 1.00 8.11 8.40 0.001406 4.54 281.97 82.96 0.31 ,R 934.00 1.00 8.11 8.40 0.001406 4.54 281.97 82.96 0.31 R 1106.00 1.00 8.59 8.91 0.001474 4.87 322.43 87.05 0.32 R• 1106.00 1.00 8.59 811 100074 187 322.43 87.05 0.32 ;3 934.00 0.80 8.21 8.41 0.000944 3.84 286.56 77.84 0.26 $t 934.00 0.80 8.21 8.41 0.000944 3.84 286.56 77.84 0.26 1106.00 0.80 8.71 8.92 0.000949 4.04 326.80 82.72 0.26 1106.00 0.80 8.71 8.92 0.000949 4.04 326.80 82.72 0.26 a `'€� Bridge 934.00 0.80 8.32 4.58 8.51 0.000877 3.74 295.24 79.36 0.25 934.00 0.80 8.31 4.58 8.51 0.000910 3.81 287.80 76.09 0.26 1106.00 0.80 8.82 5.03 9.02 0.000880 3.93 336.13 83.22 0.25 1106.00 0.80 8.81 5.02 9.02 0.000918 4.01 326.84 79.65 0.26 934.00 0.70 812 8.51 0.000740 3.56 297.46 58.35 0.24 B 934.00 170 8.32 8.51 0.000741 3.56 296.48 56.82 0.24 1106.00 0.70 8.80 9.03 0.000817 3.90 326.32 61.04 0.25 E3 1106.00 0.70 8.80 9.03 0.000819 3.91 324.26 58.93 0.25 Bf 934.00 0.80 8.39 8.70 0.001322 4.59 242.36 52.84 0.31 B 934.00 0.80 8.39 8.70 0.001322 4.59 242.41 52.85 131 l6R 1106.00 0.80 8.87 9.24 0.001431 5.01 268.29 5189 133 OR 1106.00 0.80 8.87 9.23 0.001432 5.01 268.21 5189 133 f J A-vooct U.'1 AktG l' w, HEC-RAS River: Springbrook Cr Reach:BRPS to 43rd Reach Tr Sta P. BRPS to 43rd 5 5 Plan','' 934.00 1.70 7.57 78.531 0.002943 6.04 228.01 61.89 0.46 BRPS to 4 1 5 934.00 1.70 7.57 0.002943 6.04 228,01 61.89 0.46 BRPS to 4�d 5 1106.00 1.70 8.00 0.003060 6.48 255.11 63.40 0.47 BRPS to 430 6?5 1106.00 1.70 8.00 8.53 0.003060 6.48 255.11 63.40 0.47 r_ BRPS to 5 934.00 1.70 7.80 1 8.17 0.002046 1 5.24 245.11 67.84 0.38 BRPS to o„ 6 5 [ 934.00 1.70 7.80 8.17 0.0020461 5.24 245.11 67.84 0.38 BRPS t K5 P 1106.00 1.70 8.25 8.67 0.002131 5.62 276.34 70.07 0.40 BRPS to 4" 25 1106.001 1.70 8.25 8.67 0.002131 5.62 276.34 70.07 0.40 BRPS to 43rd 6155 Fin 0 934.001 1.00 8.11 8.40 0.001406 4.54 281.97 82.96-BRPS to to 43rd 6155 934.00 1.00 8.10 8.40 0.001449 4.61 271.45 77.96 0.32 BRPS to 43rd 6155 n 1106.00 i.uvl 8.59 8.91 0.001474 4.87 322.43 87.05 0.32 rBRPS to 43rd 6155 1106.00 1.00 8.58 8.91 0.001528 4.96 308.79 80.09 0.33 BRPS to 43rd 615fi F s 934.00 0.80 8.21 8.41 0.000944 3.84 286.56 77.84 0.26 .IBRPS to 43rd 6156; 934.00 0.80 8.20 8.41 0.000977 3.90 279.58 74.68 0.26 BRPS to 43rd-` 6 „ 1106.00 0.80 8.71 8.921 0.000949 4.04 326.80 82.72 0.26 BRPS to 43rd '' 1106.00 0.80 8.70 8.93 0.000988 4.11 318.06 79.24 0.27 _ EE'•i. BRPS to 43rd ,r ' Bridge BRPS to 43rd , 934.00 0.80 8.32 4.58 8.51 0.000877 3.74 295.24 79.36 0.25 BRPS to 43rd..: €€ G 934.00 0.80 8.32 4.58 8.51 0.000907 3.80 288.23 76.16 0.26 P BRPS to 43rd ` 1106.00 0.80 8.82 5.031 9.02 0.000880 3.93 336.13 83.22 0.25 BRPS to 43rd a 1106.00 0.80 8.82 5.021 9.03 0.000914 4.00 327.38 79.67 0.26 BRPS to 43rd 62ts•> i• P '' 934.00 0.70 8.32 8.51 0.000740 3.56 297.46 58.35 0.24 BRPS to 43rd 111626 ",' „ '?' 934.00 0.70 8.33 8.52 0.000739 3.55 296.79 56.84 0.24 BRPS to 43rd $ $ 1 1106.00 0.70 8.80 9.03 0.000817 3.90 326.32 61.04 0.25 BRPS to 43rd g I 1106.00 0.70 8.81 9.03 0.000817 3.91 324.65 58.96 0.25 BRPS to 43rd 934.00 0.80 8.39 8.70 0.001322 4.59 242.36 52.84 0.31 BRPS to 411 l 934.00 0.80 8.39 8.70 0.001318 4.59 242.69 52.86 0.31 BRPS to 4 1106.00 0.80 8.87 9.24 0.001431 5.01 268.29 53.89 0.33 , BRP1o43 � l�t 1106.001 0.801 8.88 9.24 0.001428 5.00 268.56 53.90 0.33 wa,. rlt,.. iI 6VG A/ Zd O,of/ 4 a- �' S y Are WI-4- 7 - �"��f �..,�4 , � Springbrook Creek, Revised Oakesdale Project 10/10/97 U/S SW 16th Street RS=5898 o 035 Legend 16 5 - /Serf �owtr h- vcla.L. �iP o , 0/3� • U SSA �ar w5 WS Futr LU AIt3 Ch / WS Exis LU Exis Ch ■ Ground 14 - Ineff s Bank Sta 12 1 0 t = O C to CD 10 -N ^ C s o o \ r <D 6- C • � y w � o 0 0 x � a 4 N v' r coo 7 o -- - - — — T 0 50 100 150 200 Station(ft) 1 in Horiz. =30 ft 1 in Vert. =3 ft Springbrook Creek, Revised Oakesdale Project 10/10/97 S'CB:: n Chm[ffi-el impwvevflrent RS=5930 .04 >k .075 Legend 16 '. P.r Mpl ��. 70¢E3 WS Futr LU Alt3 Ch /�oS ePl 57eC40-«n /61?197 WS Exis LU Exis Ch ■ Ground 14 • Bank Sta 12 10 C O N W 6 4 2 0 100 150 200 250 Station(ft) 1 in Horiz.=30 ft 1 in Vert. =3 ft Springbrook Creek, Revised Oakesdale Project 10/10/97 E nt RS=5975 k.075->- .04 — 075 38 � Legend 16 u'��g 7 ✓ WS Futr LU AM Ch ' WS Exis LU Exis Ch Ground 14 I Apr Bank Sta 12 10 c 0 a 8 ) w 6- 4- 2- 0 -- -- --- -- - - 50 100 150 200 250 Station (ft) 1 in Horiz. =30 ft 1 in Vert. =3 ft Springbrook Creek, Revised Oakesdale Project 10/10/97 En t RS=6025 �--.075 .04- - — - r< - .075 -- - q Legend 16 �Gh�g� WS Futr LU AIt3 Ch WS Exis LU Exis Ch Ground 14 • Bank Sta 12 ll'� 4-0�d-to 10 c o 8 W 6 4 i 2- 50 100 150 200 Station(ft) 1 in Horiz.=30 ft 1 in Vert.=3 ft Springbrook Creek, Revised Oakesdale Project 10/10/97 Er4mB.Gp DT.; _h@pme'imppovement RS=6155 .075 }<----- .04 k.075s Legend 16 �lrr/ S?p, � �bfs • ` WS Futr LU AIt3 Ch Exis LU Exis Ch ■ Ground 14 • Bank Sta 12 10 o. u9 o_a 0 > 8 m w 6- 4- 2 0 50 100 150 200 Station(ft) 1 in Horiz. = 30 ft 1 in Vert. =3 ft Springbrook Creek, Revised Oakesdale Project 10/10/97 En g RS=6156 .035 .04 -.035- -- � 16 ra�tiS� S �dh 1-9 -/ rev• WS Futr L•U AIt3 Ch WS Exis LU Exis Ch Ground 14 Bank Sta 12 10 0 > 8 a� w 6- 4- 2- 0- 0 100 150 200 250 Station(ft) 1 in Horiz. =30 ft 1 in Vert. =3 ft Springbrook Creek, Revised Oakesdale Project 10/10/97 0;� Proposed Oakesdale Avenue Bridge RS=6210 035 .04 .035 o�ly'1 �lLegend 16 WS Futr LU AM Ch WS Exis LU Exis Ch F Ground 14 , Bank Sta 12 10 c 0 > 8 a) w 6- 4- 2 0 50 100 150 200 250 Station(ft) 1 in Horiz. =30 ft 1 in Vert.=3 ft Springbrook Creek, Revised Oakesdale Project 10/10/97 U/S Proposed Oakesdale Avenue Bridge RS=6210 035 - 04 03 ��r'y?w Legend 16 • WS Futr LU AU Ch WS Exis LU Exis Ch Ground 14 • Bank Sta 12 10 ■ c 0 > 8 a> w 6 4- 2- 0 50 100 150 200 250 Station(ft) 1 in Horiz. =30 ft 1 in Vert. =3 ft Springbrook Creek, Revised Oakesdale Project 10/10/97 Ent n n nrnn icco nc �r;d,e Waning RS=6264 .035 04 ---> --- .035 --� 16 egend i fe,, WS Futr LU AIt3-Ch WS Exis LU Exis Ch Ground 14 i Bank Sta 12 10 c 0 > 8 a� w 6 4I 2 0 I----- ---— 50 100 150 200 250 Station(ft) 1 in Horiz.=30 ft 1 in Vert.=3 ft �. 4� 7�?*1 "7 k 118 Springbrook Creek, Revised akesdale Project 10/10/97 Ent,a,no I IM(ee 1+50),ch-*.m nt RS=6265 k .035 >k .04 .035 Legend S4I,1d /iO,o-75 1s -I • WS Futr LU AIt3 Ch iSA �n��f�Cr+s' WS Exis LU Exis Ch ■ Ground 14 • Bank Sta 12 10 0 > 8 a� w �+►7- 6- 4- 2 0 r- 50 100 150 200 250 Station (ft) 1 in Horiz. =30 ft 1 in Vert. =3 ft r�OS S4ifi�a/� le- /l 1,7 (L°✓1 Springbrook Cieek, Revised Oakesdale Project 10/10/97 ranco 59+95),c anneMnIpTove°ment RS=6420 Fi.075 >14 .04— 0 5�/ J Legend 16 V104�Q �aC,_ O.07S Clan S/Sf1 w/ WS Futr LU AM Ch WS Exis LU Exis Ch ■ Ground 14 • Bank Sta rl 12- ��ld y►+,L 10 I I 0 I > 8 o UPS r a w 6 4 2-, 50 100 150 200 250 Station(ft) 1 in Horiz.=30 ft 1 in Vert. =3 ft OPi• , ! S�.,enS :/0 �.,� /Cvw� �Iir %S$4.n, /GW �(Gw d�2f Tti�S s P * 0/97 AM 3 /&j-Lit HEC-RAS Plan: Plan 02 River: Springbrook Cr Reach: BRPS to 43rd ,pTFlea River Q Total 4 Crif W Eteu Slope ktC� .:........:...... ,a v: :'.. ..,.. I ME a IBRPS to 43rd 5868 Bridge ,, BRPS to 43rd 5898 935.00 0.24 7.58 7 S7 3.89 7.69 0.000428 2.76 338.43 59.97 0.20 BRPS to 43rd' 5898 1389.00 0.24 8.86 g,SL 4.48 9.04 0.000477 3.34 415.60 59.99 0.22 BRPS'to 43d 5930E 1.65 7.55 � 7.77 0.002301 3.79 246.42 70.74 0.36 BRPS to 43rd 5930 1383.00 1.65 8.85 g_y/ 9.11 0.002071 4.05 341.09 74.86 0.33 u - R BRPS to 43rd' • 934.00 1.70 7.59 ? 72 7.89 0.001912 4.88 229.79 62.07 0.37 BRPS to 43rd' 1383.00 1.70 8.87 �, 9� 9.22 0.001723 5.33 312.06 66.51 0.36 BRPS to 43rd 6t}2; 934.00 1.70 7.70 -7, 1/ 7.98 0.001643 4.64 238.57 67.14 0.34 BRPS to 43rd°'. 1383.00 1.70 8.99 9 i2 9.30 0.001462 5.02 329.11 72.95 0.34 ., E� BRPS to 43rd' 615 �'� 934.00 1.00 7.94 $,3� 8.17 0.001253 4.21 267.48 80.96 0.29 BRPS to 43rd 615 ' 1383.00 1.00 9.22 cj 9.47 0.001162 4.58 378.85 92.43 0.29 BRPS to 43rd 11 615- 934.00 0.80 7.94 Q 3S 8.17 0.001131 4.09 266.18 74.18 0.28 BRPS to 43rd 1. 1383.00 0.80 9.21 9 yg 9.48 0.001125 4.59 371.61 98.00 0.29 BRPS to 43rd `° Bridge BRPS to rka 934.00 0.80 8.08 4.58 8.29 0.001033 3.96 276.24 76.01 0.27 BRPS to 43rd;; 2 1383.00 0.80 9.35 9.7�, 5.72 9.60 0.001023 4.43 385.18 98.00 0.28 MIA BRPS to 43rd g• 934.00 0.70 8.11 M3 8.29 0.000757 3.52 285.49 57.23 0.24 BRPS to 43rd: 1383.00 0.70 9.34 9,` 9.60 0.000901 4.29 364.47 76.87 0.27 BRPS to 43rd= ( 934.00 0.80 8.19 ;,yy 8.48 0.001326 4.51 231.94 52.57 0.31 BRPSto43rd 1383.00 0.80 9.43 ?,9� 9.82 0.001460 5.31 299.89 57.07 0.34 P Coh ,S� ory, ese cam rL+,,5 ve4�• N ' s��.�C - I- --j. 1, � '��n /� S Gaa`�' S�drr�,�,�- ll �c� S� �r.� l ^�-i, i c 1 S A s v6�.)4✓r f i ar (°4,S a( CAfd a `ten/' In c/�s e l-� t,�S C�e✓. e4, '2- S-Q2 a -d " W/ JoL gr h-li+c A�t_ ��ArJ �' �le4.,*4 le,, 7) Ic / '3 yA F��� �� �.,�4,,� l� fah / / "� 5W /��� TI �� 6L�2.o �.o„ �►+� lWJ �lG�.� �i�24.. � ��i1S547L �L(C� HEC-RAS Plan:Plan 02 River: Springbrook Cr Reach: BRPS to 43rd .. yy -r a ...i. .. IE'•:' GPM .'_ e► Sia Q Tatal ip Ch o f Cnt W.S. EG' <<E (Cfs) (ft 55868 Bridge h iE: 5898 935.00 3.50 7.59 5.46 7.82 0.001232 3.81 245.18 59.97 0.33 5898 1389.00 3.50 8.86 6.05 9.15 0.001105 4.32 321.25 59.99 0.33 5930 934.00 4.00 7.62 7.91 0.003475 4.33 215.54 70.97 0.44 5930 1383.00 4.00 8.91 9.22 0.002781 4.47 309.28 75.04 0.39 S 59T5 934.00 4.00 7.72 8.10 0.003665 5.40 194.10 62.51 0.49 3 5975 1383.00 4.00 8.96 9.37 0.002811 5.73 274.00 66.80 0.45 g t td! 6025 934.00 4.00 7.91 8.28 0.003343 5.33 200.12 68.68 0.48 rd' 6025 1383.00 4.00 9.12 9.51 0.002511 5.53 286.31 73.46 0.43 �S 6155 934.00 4.00 8.37 8.66 0.002500 4.87 231.77 85.17 0.42 t 3rd 615 1383.00 4.00 9.51 9.81 0.002016 5.12 334.13 94.91 0.39 rd 6156 934.00 4.00 8.35 8.67 0.002657 5.00 218.51 79.78 0.43 Ord' 6156 1 1383.00 4.00 9.49 9.82 0.002119 5.23 319.95 98.00 0.40 43r i 6210 Bridge 43 ' 6264 934.00 4.00 8.67 6.97 8.92 0.001941 4.48 244.19 82.54 0.37 E ER. RR" 4r 6264 1383.00 4.00 9.75 7.65 10.03 0.001683 4.81 345.45 98.00 0.36 v 60 934.00 4.00 8.63 8.94 0.002106 4.67 216.58 60.11 0.39 R 4 5 1383.00 4.00 9.67 10.07 0.002183 5.46 290.47 77.54 0.41 a20 934.00 4.00 8.94 9.31 0.002477 5.26 202.84 55.42 0.42 NCI Qf 1383.00 4.00 9.97 10.47 0.002607 6.14 261.76 58.89 0.45 �55�,-rt¢�f ( �c,r �lcW (�i„e(Pi" ��c�3.t �� �`� �b �f.�✓ �. ��1/0//*/S? n-v kcs do,,. zd /Q( / HEC-RAS River:Springbrook Cr Reach:BRPS to 43rd / /otrU,- �_ „ Reach Ri,;, {a Plarf 1pv Grit W S: E.G. Elev E.G Slope Chnl Flow Area Top Width_ Froude#Chl 3 _ ft) (ft ft) iuB (ft) BRPS to 43rd ' 4947 i Plan 03 x 1044.00 1.00 7.17 7.31 0.000528 3.01 347.26 63.87 0.23 ,JRRPS to 43rd 4947, Plan 02 1044.00 1.00 7.17 7.31 0.000528 3.01 347.26 63.87 0.23 BRPS to 43rd 4950 Plate 03 E; 1044.00 1.00 7.15 3.96 7.34 0.000196 3.50 298.40 55.01 0.25 BRP to 43rd 4950,1 Plan 02 , v 1044.00 1.00 7.15 3.96 7.34 0.000196 3.50 298.40 55.01 0.25 T, 13RPS to 43rd 5050, Flan 03_ ", 935.00 1.00 7.22 3.80 7.37 0.000152 3.09 302.33 55.01 0.22 kIRPS t4 Ord \= $050, Plan 02 935.00 1.00 7.22 3.80 7.37 0.000152 3.09 302.33 55.01 0.22 f3RPta 43rd 5100_ Plan 03 935.00 1.00 7.23 3.80 7.38 0.000151 3.09 302.74 55.01 0.22 --. BRPSta 43rd 5100" Plan 02 s 935.00 1.00 7.23 3.80 7.38 0.000151 3.09 302.74 55.01 0.22 i BRPS to 43rd 51 03 935.00 0.09 7.24 3.69 7.391 0.000140 3.02 309.51 55.01 0.22 "to Otd:: $14 _£ 0 935.00 0.09 7.24 3.69 7.39 0.000140 3.02 309.51 55.01 0.22 BRPS to 43rd„ 5268 Plan 03 935.00 -0.45 7.37 7.41 0.000166 1.67 563.27 100.36 0.12 BRPS to 43rd: 5268,', Plan 02, 935.00 -0.45 7.37 7.41 0.000166 1.67 563.27 100.36 0.12 BRPS to 43rd 5348 Plan 03. 935.00 0.12 7.38 7.43 0.000214 1.77 527.75 94.30 0.13 BRPS to 43rd f5348 Plan 02 935.00 0.12 7.38 7.43 0.000214 1.77 527.75 94.30 0.13 BRPS to 43rd,•' S393 Mult Open BRPS to 43rd 5439 Play ' 935.00 0.12 7.40 3.24 7.45 0.000244 1.75 533.17 111.03 0.14 PS`,t0 43rd „5438' Purr 935.00 0.12 7.40 3.24 7.45 0.000244 1.75 533.17 111.03 0.14 �$w\aRP,S to 43rd 5550 .Plan 935.00 0.16 7.42 7.46 0.000269 1.74 543.66 111.78 0.14 935.00 0.16 7.42 7.46 0.000269 1.74 543.66 111.78 0.14 01 PS to 43rd 5773 Plan 935.00 0.12 7.43 7.59 0.000759 3.28 298.51 56.77 0.24 to 43rd 5773= Plan O 935.00 0.12 7.43 7.59 0.000759 3.28 298.51 56.77 0.24 8M 43rd�p, 5830 935.00 0.23 7.55 7.65 0.000470 2.47 386.31 74.95 0.19 RP 43rd:' 5830 flark 935.00 0.23 7.55 7.65 0.000470 2.47 386.31 74.95 0.19 ' 43rd 533 Plan 0935.00 0.24 7.54 3.89 7.66 0.000437 2.78 336.42 59.97 0.21 43rd 58 Plarr 935.00 0.24 7.54 3.89 7.66 0.000437 2.78 336.42 59.97 0.21 E. 0 43rd 586. Bridge # �-vr• >r S U/S G J� 6,A /t� St v /bf-A so- O .C>S d i t�..���/ � �A�S lrin 1 ND �/�`,C !� �/S �'G yS �✓ � �rl ��//�-�u. S HEC-RAS River:Springbrook Cr Reach:BRPS to 43rd(Continued) ch tverSla Pfan Q Total \ (of$) ; BRPS' a 43rd:` .5898 Plan 03 935.00 0.24 7.58 3.89 7.69 0.000428 2.76 338.43 59.97 0.20 BRPS to 43rd.. 5898 Plart.g2,.: 935.00 0.24 7.58 3.89 7.69 0.000428 2.76 338.43 59.97 0.20 �E BRPS to 4 rd 5930 Plan 03 934.00 1.65 7.56 7.78 0.007894 3.78 247.16 70.80 0.36 BRPS to 43rd 5930 Plan 02 - 934.00 1.65 7.55 7.78 0.003505 3.79 246.68 70.76 0.36 BRPS to 43rd 5975 Plan 03 M�! MW 934.00 1.70 7.57 8.02 0.002209 5.98 244.21 66.13 0.45 ',BRPS to 43rd 5975 -77 934.00 1.70 7.59 7.91 0.001672 5.22 245.95 66.27 0.39 IF BRPS to 43rd 6025 Plan 03 934.00 1.60 7.75 8.12 0.001595 5.24 259.47 71.241 0.38 BRPS to 43rd 6025 Plan 02 ar 934.00 1.60 7.69 7.99 0.001367 4.82 255.41 70.88 0.35 `BRPS to 43rd 6155 Plan 03 934.00 1.00 7.98 8.31 0.001223 4.78 271.34 81.73 0.33 _ _ ,.. . ,BRPS to 43rd 6155 Plan 02 ' ..' 934.00 1.00 7.86 8.16 0.001167 4.61 261.74 79.81 0.32 BRPS to 43rd 6156 Plan 03 934.00 0.80 8.07 8.32 0.000912 4.25 275.38 75.86 0.29 BRPS to 43rd 6156 Plan 02. ' ' 934.00 0.80 7.88 8.16 0.001022 4.42 261.73 73.35 0,31 hR:i•E.i. BRPS to 43rd 6210 Bridge BRPS to 43rd 6264 Plan 03 D _ 934.00 0.80 8.17 4.57 8.41 0.000853 4.16 283.73 77.35 0.28 BRPS to 43rd f c4 Plan 02 934.00 0.80 8.01 4.57 8.27 0.000947 4.30 270.87 75.04 0.30 BRPS to 43rd',,E Plan 03 i, 934.00 0.70 8.22 8.42 0.000600 3.62 291.83 57.84 0.24 $RPS to 43rd Plat02 .«_ 934.00 0.70 8.07 8.27 0.000627 3.65 283.32 57.02 0.25 BRPS to 43rd PJ,a 03 " 934.00 0.80 8.25 8.58 0.001100 4.73 235.78 53.55 0.32 PS to 43rd =' 0 934.00 0.80 8.11 8.44 0.001132 4.73 228.57 52.71 0.33 Ply,r .3 ; /✓-�Os4 CI,,,4 -tiry� � ?.- "I.e-3 4k�5�, 4-e� /100107 Pl H, -z- r / as 4r `.4",4 �^ HEC-RAS River:Springbrook Cr Reach: BRPS to 43rd r��le /� 1 9- LI F/.n, River S t a leu Cnt W.S. E.G.Elev E.G Sty Flow Area Top Width {ft3 €iiio y1!t (5q ft) (ft) . . 58G8" aEi a Bridge \EE, BtSfa43td 5898= 1389.00 0.24 8.86 4.48 9.04 0.000477 3.34 415.60 59.99 0.22 43rd 5898 \\ P a Rim 1389.00 0.24 8.86 4.48 9.04 0.000477 3.34 415.60 59.99 0.22 PS to 43rd 5930 1383.00 1.65 8.86 9.12 0.006440 4.05 341.93 74.93 0.33 S to 43rd 5930 1383.00 1.65 8.85 9.11 0.003020 4.05 341.35 74.87 0.33 �BRPS to 43rd S 1383.00 1.70 8.80 9.37 0.002213 6.85 327.86 69.83 0.47 BRPS to 43rd 1383.00 1.701 8.86 9.24 0.001578 5.82 332.52 70.08 0.39 VIEW . $RPS to 43rd 5=' FEt 1383.00 1.60 8.99 9.47 0.001658 6.08 352.60 77.54 0.40 BRPS to 43rd 6 \\ 1383.00 1.60 8.97 9.32 0.001304 5.38 350.77 77.46 0.36 BRPS to 43rd �', �� Flag E ', 1383.00 1.00 9.25 9.67 0.001305 5.56 382.12 92.75 0.35 ;BRPS to 43rd ? Flan 1383.00 1.00 9.14 9.48 0.001139 5.15 372.08 91.80 0.33 v I BRPS to 43rd, �CE,,Plan 1383.00 0.80 9.39 9.68 0.000902 4.77 389.20 98.01 0.30 BRPSlo43rd 6' Plana ; 1383.00 0.80 9.13 9.48 0.001098 5.15 363.89 98.00 0.33 BRPS 8rd tf, Bridge BRPS 643rd 6 Plan t} 1383.00 0.80 9.50 5.65 9.78 0.000844 4.66 400.20 97.91 0.29 a BRP 43rd' 1383.00 0.80 9.27 5.65 9.60 0.001008 4.99 377.65 98.00 0.31 BRPS 1a 43rd5 IN Fta E 1383.00 0.70 9.50 9.78 0.000707 4.41 376.68 77.10 0.27 6 R MMa43rd 6 G5 Planz <EE 1383.00 0.70 9.31 9.61 0.000758 4.49 362.25 76.81 0.28 »,. ES3.l f tae43rd 6 20 ,Ptah Q ,e' 1383.00 0.80 9.52 9.98 0,001251 5.67 307.88 59.01 0.36 _-.. BRPS 4�43rs� Plan 1383.00 0.80 9.36 9.80 0.001260 5.61 298.66 58.80 0.36 �a r* �o�ucr- �j V-1- C.ancLt,Sr�� ��✓/S/ eSe dl�vti�Cf 4-4)-Q�j �lGl� 3 Pry ac¢/ ar"e.l - 41 yam►- 0-Vk(ti4e4 (0•O/ �� /,/A/00 7 Plyn Z �r�PuS�Ayn �1 ��.tn �`Jt �jodivr HEC-RAS River:Springbrook Cr Reach: BRPS to 43rd 1*0,-C, �e A (f- f low /00- x n _ _ IV OEM Pf' Q Bridge '03: I-JOW.UU1 0.24 8.86 4.48 9.04 0.000477 3.34 415.60 59.99 0.22 5 3E tl2 1389.001 0.241 8.86 4.48 9.04 0.000477 3.34 415.60 59.99 0.22 i�. 03 1383.00 1.65 8.86 9.12 0.006987 4.04 341.91 74.90 0.33 �3,.',„' c�`" 02i 1383.00 1.65 8.85 9.11 0.003020 4.05 341.35 74.87 0.33 1383.00 1.70 8.79 9.39 0.002291 6.97 327.63 69.87 0.47 02 1383.00 1.70 8.86 9.24 0.001578 5.82 332.52 70.08 0.39 Ei S 3' 1383.00 1.60 9.02 9.49 0.001641 6.06 354.41 77.61 0.40 0Z 1383.00 1.60 8.97 9.32 0.001304 5.38 350.77 77.46 0.36 EEF HH, to 43:;• p3':: 1383.00 1.00 9.27 9.69 0.001296 5.55 383.94 92.90 0.35 kS t0 1383.00 1.00 9.14 9.48 0.001139 5.15 372.08 91.80 0.33 E. i 3 u 1383.00 0.80 9.39 9.70 0.000938 4.87 389.34 98.00 0.30 1383.00 0.80 9.13 9.48 0.001098 5.15 363.89 98.00 0.33 �h Bridge ram. 1383.001 0.801 9.51 5.65 9.80 0.000876 4.75 400.80 98.00 0.29 2,_._ 1383.00 0.80 9.27 5.65 9.60 0.001008 4.99 377.65 98.00 0.31 p S 10 26' 1383.00 0.70 9.51 9.80 0.000719 4.45 377.55 77.22 0.27 8 • ,,1a. ;,,_i 1383.00 0.70 9.31 9.61 0.000758 4.49 362.25 76.81 0.28 P5 1383.00 0.80 9.54 Qj - 9.99 0.001242 5.65 309.26 59.14 0.36 R 1383.00 0.80 9.36 9.80 0.001260 5.61 298.66 58.80 0.36 51.E Szq� f� 62c y aZ-= 3CC , 5' �- o��,- cam. 00/�7� 7 �tf 3 / Sw /C<1, c �� 0 •000782 or ,� �Q�2u°O(,o Q,�tdC z113 of l -!c 2 `1Pibf �' �•, �` Ce CS G/C�� %S/� s � {.a,,, / mc ar , / d l S O.Ooo 1Yb ��/ef s u mow.. � / 1',t,-(�' 44,4.de t �icsl l^j Gi �Y�1�I�C h, �Yn,,nrc (,tea.IP, 7-0- ct 1p*. c->, 7 r6- 6LW7�4d 410ec*1 a;� , cn, 64'o� /, <�2�ce,dt,., ©S, 3 1It f&S-ed ""n c� - -,� -C lu�"G f HEC-RAS River:Springbrook Cr Reach:BRPS to 43rd / /O YI!�. �Z LG Usk oo-q k Reach Rivet c° _r PS'to 43rd 5868 Bridge .. _ i r I BRPS to 43rd 5898iF 935.00 0.24 7.58 3.89 7.69 0.000428 2.76 338.43 59.97 0.20 ERRS to 43rd 5898-, 935.00 0.24 7.58 3.89 7.69 0.000428 2.76 338.43 59.97 0.20 S to 43rd 5898 935.00 0.24 7.58 3.89 7.69 0.000428 2.76 338.43 59.97 0.20 BRPS to 43rd 5930 934.001 1.65 7.56 7.78 0.008381 3.78 247.16 70.78 0.36 BRPS to 43rd 5930 934.00 1.65 7.55 7.78 0.003505 3.79 246.68 70.76 0.36 BRPS to 43rd 5930 934.00 1.65 7.371 7.97 0.010088 6.22 150.18 45.22 0.60 $RPS to 43rd 5975 ";. 934.00 1.70 7.57 8.03 0.002252 6.04 244.36 66.20 0.45 BRPS to 43rd 5975 934.00 1.70 7.59 7.91 0.001672 5.22 245.95 66.27 0.39 BRPS to 43rd 5975„ 934.00 1.70 7.65 8.36 0.006236 6.83 147.06 34.93 0.52 BRPS to 43rd 6025 934.00 1.60 7.76 8.14 0.001581 5.23 260.46 71.33 0.38 BRPS to 43rd 6025 934.00 1.60 7.69 7.99 0.001367 4.82 255.41 70.88 0.35 BRPS to 43rd 6025 ? 934.00 1.60 8.08 8.53 0.001739 5.47 186.62 37.34 0.39 $RPS to 43rd 6155o, 934.00 1.00 7.99 8.32 0.001215 4.77 272.30 81.91 0.33 BRPS to 43rd 6155 1 934.001 1.00 7.86 8.16 0.001167 4.61 261.74 79.81 0.32 $RPS to 43rd 6155 934.00 1.00 8.42 8.71 0.000961 4.38 225.83 40.59 0.30 BRPS to 43rd 6156 934.00 0.80 8.08 8.33 0.000906 4.24 276.24 76.01 0.29 `BRPS to 43rd '6156 934.00 0.80 7.88 8.16 0.001022 4.42 261.73 73.35 0.31 BRPS to 43rd 6210 Bridge i BRPS to 43rd 6264 934.00 0.80 8.19 4.57 8.42 0.000848 4.16 284.54 77.49 0.28 BRPS to 43rd 6264 i ; 934.00 0.80 8.01 4.57 8.27 0.000947 4.30 270.87 75.04 0.30 BRPS to 43rd 6265\� 934.00 0.70 8.23 8.43 0.000597 3.62 292.41 57.90 0.24 BRPS to 43rd 934.00 0.70 8.07 8.27 0.000627 3.65 283.32 57.02 0.25 B ___.. BRPS to 43rd 6285 934.00 0.70 8.61 8.80 0.000550 3.54 280.00 47.66 0.23 BRPS to 43rd =:' 642Q;' 934.00 0.80 8.26 p,�tZ'r , 8.59 0.001094 4.72 236.49 53.69 0.32 r BRPS to 43rd .; 8420`.,llll 934.00 0.80 8.11 O.S3 . 8.44 0.001132 4.73 228.57 52.71 0.33 BRPS to 43rd "A"'ll0420 934.00 0.80 8.64 8.95 0.000972 4.51 232.81 45.88 0.30 4 THE CITY OF RENTON DEPARTMENT OF PL NNING/ ILDING/ UBLI WOR KS - FOURTH FLOOR - 200 MILL AVENUE SOUTH RENTON, WASHINGTON 98055-2189 FAX: 235-2541 ------ To: gru-Ce Company: Phone: Fax: q,5 y- 0220 From: 5c:otrv- Company: Phone: Fax: Date: /(//2/9'7 Pages including this cover page: Comments: /1 e- f000t)' 64 VO et/ �Os Jv1 � Vut1 � W St On 1415 4) / �-- S�� ON + @ SW 27th Street (i July — 15 September) @ Interstate 405 (1 July — 15 September) 100 C , M C- CU cn U / 10 o , f0 /, * CD +* � ♦/� + i i i / i i i 1 � .001 .01 . 10 .50 .90 .99 .999 Cumulative Probability (P) East Side Green River Watershed — Hydrologic Analysis Simulated Peak Flows in Springbrook Creek i000 + @ SW 27th Street (August Only) @ Interstate 405 (August Only) , 100 , / CD CM L / fD L U En 10 o , a. ' ' + +++ .001 .01 . 10 .50 .90 .99 .999 Cumulative Probability (P) East Side Green River Watershed - Hydrologic Analysis Simulated Peak Flows in Springbrook Creek THE CITY OF RENTON DEPARTMENT OF AgO w , PLANNING/BUILDING/PUBLIC WORKS FOURTH FLOOR 200 MILL AVENUE SOUTH FY, RENTON, WASHINGTON 98055-2189 FAX: 235-2541 ` n 41M To: Gregg Farris Company: Phone: 454-5600 Fax: 454-0220 From: Scott Woodbury Company: Phone: 277-5547 Fax: 235-2541 Date: 10/01/97 Pages including this cover page: 6 Gregg: Following are my comments to your memo on the HEC-RAS analysis. Please call me after you have had a chance to review the comments. f top f-Y, Submittal 8B-(1 0-Year) Channel improvements SW 16th to P-9, remove bridge d/s of 27th, anal-impro ements 31 st to railroad bridge with wetland bank. Same as Submittal 8A, except Change Oakesdale replaced with multiple box(two 30'spans, open bottom). from future Change US Velocity 100-year cond./exist. Branch IDS Ws US Ws US Ws from Invert Max Q Range HU1000 Target I channel No. I Distance Distance Elev. Elev. Prev.Run Prev.Run Elev. (cfs) (fps) Headloss Ft. Elevs. elevs. Springbrook Creek 72 0.37 1,954 4.35 5.18 5.18 0.00 0.0 1609 0.83 0,42 Forebay 0.52 1 0.16 845 5.18 6.62 6.61 0.01 0.2 1611 2.0-5.5 1.44 1.70 0.85 4 0.08 422 6.82 7.18 7,17 0.01 0.3 1422 0.35 0.84 0.94 5 0.33 1,721 7.18 8.39 8.39 0.01 1.0 1422 1.22 0.71 1.02 6 0.13 686 8.60 8.68 8.67 0.01 0.8 0.08 0.12 U/S Grady Way 1.01 7 0.01 42 8.68 8.69 8.6B 0.01 1.2 0.01 0.29 1.01 9 0,01 74 8.69 8 8.37 0.01 0.3 1415 3.0-5.7 -0.31 -4.22 D/S SW 16th 0.97 10 0.22 1,151 8.93 10.80 10.79 0.01 1.2 1415 UO.4 1.63 -0.54 ^ j 13 0.10 502 10.82 11.13 11.12 0.01 1.3 1379 0.63 D/SSW19th 0.49 /1 t D,00099y �t/�f 3 M 5 14 0.15 776 11.17 11.65 11.63 0.01 1.4 1288 0.61 -0.4916 0.16 850 11.65 12.19 12.18 0.01 1.4 1286 0.64 -0.44 0.12 634 12.22 1 .4 12.46 0.01 0.0 1176 Confluence of P-9 -0.39 18 0.01 48 12.47 12.55 12.54 0.01 0.0 1187 0.08 1.58 -0.37 19 0.10 507 12.55 12.64 12.63 0.01 0.0 1167 0.09 0.18 -0.52 20 0.02 90 12.67 12.72 12.71 0.01 0.2 1188 0.05 0.53 U/S 27th -2.95 21 0.22 1,140 12.73 12.84 12.83 0.01 3.5 1295 0.11 0.10 -2.92 23 0.11 591 12.B4 13.21 13.20 0.01 4.1 1294 0.37 0.63 -2.60 24 0.09 449 13.21 13.57 13.55 0.01 4.6 1297 0.35 0.79 -2.31 25 0.01 53 13.59 13.63 13.62 0.02 4.6 1215 0.04 0.85 13.6 D/S 34th -2.28 26 0.19 1,003 13.72 14.27 14.25 0.03 4.7 1218 0.55 0.55 U/S 34th -1.95 27 0.18 961 14.27 14.97 14.94 0.03 4.4 1256 0.69 0.72 -1.42 30 0.05 280 15.30 15.94 15.90 0.04 4.3 1257 3.9-4.2 0.64 2.29 14.5 43rd system outfall -0.94 31 0.17 992 16.11 16.58 17.46 -0.88 5.5 1167 0.48 0.53 -1.50 33 0.17 919 16.59 17.05 17.81 -0.76 5.7 1156 0.47 0.51 D/S 43rd -1.28 34 0.03 18 17.93 17.97 18.83 -0.86 5.5 1157 0.03 1.83 18.0 U/S 43rd -1.54 Panther Creek 45 0.01 26 12.47 12.47 3.7 125 0.00 0.00 450 0.18 945 12.22 12.25 3.9 127 0.03 0.03 \CCCyyy)\) 46 0.08 438 12.54 12.55 4.3 124 0.01 0.03 S 47 0.16 850 12.55 12.58 5.1 163 0.03 0.04 13.0 D/S E.Valley Hwy f 81 0.02 100 13.32 13.32 7.0 107 1.2-2.3 0.00 0.04 80 0.00 10 13.85 13.85 9.0 107 0.00 0.00 n Wetlands 3 12.55 Along reach 47 6 N/A Along reach 21(u/s 27th) Q 7A 12.75 Along reach 21(u/s 271h) 713 13.02 Along reach 21(Ws 271h) 7C 13.75 Along reach 21(u/s 27th) \ 10 14.27 Along reach 27(city wetland bank) } 11A 16.13 North PCW 11B 16.13 Central PCW 11 16.13 South PCW H:DO S,: lI I I.%LS:SWM V\ � N\ Page 1 J • HEC-RAS Plan: Plan 02 River:Springbrook Cr Reach: BRPS to 43rd(Continued) Reach River Sta Q T Min Ch> I Criti lli!S .... BRPS to 43rd S38 1389.00 0.24 8.82 4.48 9.00 0.000486 3.36 413.24 59.99 0.23 BRPS to 43rd 868 Bridge SG+ AA ¢r BRPS to 43rd 98 1389.00 0.24 8.86 4.48 9.04 0.000477 3.34 415.60 59.99 0.22 BRPS to 43rd 30 1383.00 1.65 8.85 9.11 0.003020 4.05 341.35 74.87 0.33 ' 3" BRPS to 43rd 975 1383.00 1.70 8.86 9.24 0.001578 5.82 332.52 70.08 0.39 4f/= 9. BRPS to 43rd 25 1383.00 1.60 8.97 9.32 0.001304 5.38 350.77 77.46 0.36 BRPS to 43rd 85 1383.00 1.00 9.14 9.48 0.001139 5.15 372.08 91.80 0.33 BRPS to 43rd %55 1383.00 0.80 9.13 9.48 0.001098 5.15 363.89 98.00 0.33 z o,00112 f��� - %L BRPS to 43rd 1t� „ Bridge Qq " BRPS to 43rdt 64 1383.00 0.80 9.27 , 5.65 9.60 0.001008 4.99 377.65 98.00 0.31 BRPS to 43rd 5 , 1383.00 0.70 9.31 9.61 0.000758 4.49 362.25 76.81 0.28 d BRPS to 43rdW, . .8 0.001260 5.61 298.66 58.80 0.36 RPS to43_d � g'fy 1383.00 a. . . . . . . . BRPS to 43rd $\ , 1347.00 1.40 12.96 8.62 13.10 0.001263 3.05 440.93 715.03 0.24 AM �BRPS to 43rd 1347.00 1.20 13.49 6.49 13.52 0.000290 1.81 1182.30 711.37 0.13 BRPS to 43rdI'll385 1254.00 - �t,1.60 13.54 7.01 13.54 0.000032 0.52 4997.37 2105.62 0.04 BRPS to 43rd' 987 .' 1254.00 0.00 13.54 5.24 13.59 0.000200 1.88 1220.30 624.92 0.16 BRPS to 43rd,'; 8 1254.00 0.00 13.52 4.39 13.63 0.000270 2.83 911.96 568.03 0.17 BRPS to 43rd,'; 5 Bridge S to 43rd"',, POD= 1254.00 0.00 13.62 4.38 13.69 0.000564 2.49 966.59 570.43 0.15 PS to 43rd _ I 1254.00 0.00 13.71 6.50 13.72 0.000154 1.17 1792.80 498.42 0.09 S to 43rd ( 1254.00 0.00 13.77 5.40 13.79 0.000178 1.47 1361.03 323.57 0.10 PS to 43rd', 1254.00 0.00 13.64 5.15 13.95 0.000524 4.49 279.01 322.56 0.22 PS to 43rd $ Culvert BRPS to 43rd 1147.00 0.20 16.76 4.69 16.80 0.000086 1.72 665.46 2858.20 0.09 BRPS to 43rd 1147.00 0.20 16.82 4.68 16.82 0.000003 0.22 10817.86 2985.76 0.01 BRPS to 43rd 1147.00 0.20 16.82 4.67 16.82 0.000003 0.22 10827.21 2986.23 0.01 F BRPS to 43rd = E ''. 1147.00 3.50 16.81 7.81 16.83 0.000084 1.15 2440.00 2246.94 0.07 �+ BRPS to 43rd 1147.00 4.60 16.94 9.13 16.95 0.000177 1.12 2033.88 2304.65 0.09 Q BRPS to 43rd 1 i 1147.00 4.60 16.93 8.64 16.97 0.000087 1.65 1660.68 2334.11 0.10 BRPS to 43rd 1 Culvert BRPS to 43rd H 1217.00 4.20 16.95 7.05 16.97 0.000094 1.21 2142.15 2287.51 0.08 Q _BRPS to 43rd 1217.00 4.20 16.95 8.20 16.97 0.000190 1.31 2089.84 2484.12 0.10 kA r2 BRPS to 43rd 9 5 1217.00 4.70 17.14 9.20 17.21 0.000292 2.19 555.17 320.05 0.14 ,BRPS to 43rd $,0E€e 1217.00 4.40 17.40 9.66 17.55 0.000374 3.11 921.75 1733.58 0.18 BRPS to 43rd_. a 6 1217.00 4.401 17.42 9.66 17.56 0.000371 3.10 949.361 1776.19 0.18 Aft w� r w y s HEC-RAS Plan: Plan 02 River: Springbrook Cr Reach: BRPS to 43rd(Continued) Reach River Sta Q Total Min Ch El W.S.Elev Crit 1 � � � �� E.G. Slope Vel Chnl Flow Area Top Width Froude_#�Ch,i, -_ - i= � (ft} (ft) :'r� � ' _� (ff ft) (ftls) (sq it) 1 -(h) ._ ._........... -- ... ._._ BRPS to 43rd 1490 Bridge BRPS to 43rd 149a5 1217.00 4.40 17.57 9.65 17.71 0.000342 3.01 1258.20 2148.70 0.17 BRPS to 43rd 1499,5 1217.00 4.30 17.62 17.74 0.001029 2.80 493.17 190.65 0.20 BRPS to 43rd 15225 ,; . 1217.00 4.30 17.85 17.96 0.000889 2.67 540.97 218.77 0.18 BRPS to 43rd '15275 1256.00 4.30 17.88 10.39 18.00 0.000540 2.87 546.55 221.82 0.18 BRPS to 43rd 15346.5 Culvert BRPS to 43rd 15418 191164.00 4.70 17.94 9.55 18.01 0.000290 2.19 1040.39 1869.45 0.13 S to 43rd 15468 1164.00 4.70 17.97 18.03 0.000373 2.05 1125.42 2072.05 0.14 1164.00 5.50 18.26 10.23 18.33 0.000327 2.18 593.84 186.20 0.14 1164.00 5.70 18.50 18.56 0.000210 1.91 670.21 202.07 0.12 1155.00 5.70 18.52 18.57 0.000206 1.89 672.611 208.09 0.11 6, 3 (r �V/ fl",� IC HEC RAS River Springbrook Cr Reach BRPS to 43rd I Ruch Rid g Plan,'�61 Min Ch EI 1 Efev ( �u SI .l. E€`.,.... B 1p43rd 86 Bridge Ft E. Ei Y E lq� E a tan 01 935.00 0.24 7.58 3.89 7.69 0.000428 2.76 338.43 59.97 0.20 IRP, to 43rd„ 58 PtaCt 03 a 935.00 0.24 7.58 3.89 7.69 0.000428 2.76 338.43 59.97 0.20 Q t3 R i'tan 01 =`: t` 1110.00 0.24 8.03 4.13 8.18 0.000466 3.03 365.77 59.98 0.22 5 Eu Plan 03 1110.00 0.24 8.03 4.13 8.18 0.000466 3.03 365.77 59.98 0.22 x WAI 1 l (an 01 934.00 1.65 7.37 7.97 0.010088 6.22 150.18 45.22 0.60 tt S9� Plan 03 934.00 1.65 7.55 7.78 0.003505 3.79 246.68 70.76 0.36 • '�• �€€ ,. li;Flan 01 1106.00 1.65 7.82 8.47 0.010132 6.47 170.90 47.59 0.60 E...n i 5 Plan 03 '``IM • 1106.00 1.65 8.01 8.26 0.003420 3.96 279.56 72.21 0.35 4 R � 8 plan 01 1 1 934.00 1.70 7.65 8.36 0.006236 6.83 147.06 34.93 0.52 ;Plan 03„ E, 934.00 1.70 7.59 7.91 0.001672 5.22 245.95 66.27 0.39 C P # Plan 1106.00 1.70 8.06 8.89 0.006749 7.46 161.52 36.36 0.55 d 59Z Plan 03 1 1106.00 1.70 8.04 8.40 0.001700 5.54 276.08 67.62 0.40 E. EENORE E a a 1 ...t.z '::•. ...... 13FF� tGt E; F?tan 01 r� 934.00 1.60 8.08 8.531 0.001739 5.47 186.62 37.34 0.39 ip 60 iaCt 03 934.00 1.60 7.69 7.99 0.001367 4.82 255.41 70.88 0.35 «tit 6025 tt 0fl1106.00 1.60 8.55 9.09 0.001889 5.99 204.35 38.55 0.41 SAP td 60 FIr ; art 03 1106.00 1.60 8.15 8.48 0.001402 5.14 288.28 73.76 0.36 BFp a+3rd 0� c E 934.00 1.00 8.42 CL i 8.71 0.000961 4.38 225.83 40.59 0.30 BRPS f0 43rd5 'a 934.00 1.00 7.86 8.16 0.001167 4.61 261.74 79.81 0.32 6RPbi1 € 1' 1106.00 1.00 8.93 9.28 0.001046 4.80 247.08 42.06 0.31 Bl t0 615 .fit 1106.00 1.00 8.33 8.65 0.001206 4.91 299.95 84.80 0.33 11e BRP Q C1 ; a ,. 03 •,. E ;;' 934.00 0.80 7.88 8.16 0.001022 4.42 261.73 73.35 0.31 >31i1 ! T n 03 M 1106.00 0.80 8.34 8.65 0.001085 4.76 296.42 79.56 0.32 mp B � 0 934.00 0.80 8.01 4.57 8.27 0.000947 4.30 270.87 75.04 0.30 BRP f0 43rd �2 3 1106.00 0.80 8.47 5.01 8.76 0.001003 4.64 307.10 81.38 0.31 511,11 MI. ARP 43rd € g P 934.00 0.70 8.61 8.80 0.000550 3.54 280.00 47.66 0.23 E 934.00 0.70 8.07 8.27 6.000627 3.65 283.32 57.02 0.25 R�' t 43rd , 1106.00 0.70 9.15 9.38 0.000601 3.88 306.49 49.88 0.25 N N Pa43rd 1106.00 0.70 8.53 8.77 0.000692 4.01 310.08 59.57 0.26 I? is rd €r 8 ER1 0•. --,: E_- 934.00 0.80 8.64 - 8.95 0.000972 4.51 232.81 45.88 0.30 NA 934.00 0.80 8.11 8.44 0.001132 4.73 228.57 52.71 0.33 1 Sean S. Woodbury From: Bob Elliot To: Swoodbury; jensen Subject: HEC-RAS Date: Wednesday, January 01, 1997 8:43AM < <File Attachment: HECRAS.ZIP> > From: Bob Elliot Date: Wed, Sep 17, 1997 8:43 AM Subject: HEC-RAS To: jensen; Swoodbury Bruce & Scott, Attached is a zipped up file containing input & output for the Springbrook Creek HEC-RAS model. It is set up as one project with two plans: Plan 01 (sprngbrk.p01): Existing channel geometry (sprngbrk.g01) Discharge input for 2 runs (sprngbrk.f01) -existing land use, exising channel -future land use, exising channel Plan 02 (sprngbrk.p02): Oakesdale grade plan & bridge(sprngbrk.g02) Discharge input for 3 runs (sprngbrk.f02) -existing land use, exising channel -future land use, exising channel -future land use, Alt 3 channel Note that there is no geometry input for the ESGRWP Alt 3 channel, only discharge input from the ESGRWP study. I've added as high water mark information for each profile the corresponding stated water levels from the ESGRWP, so we can see how well HEC-RAS compares with FEQ. The Manning n values are somewhat arbitrary for the reach with the grading improvements. I used 0.035 for the low flow channel bottom (same as used for existing condition run) and 0.050 for the graded Page 1 portions of the banks (compared to 0.075 for existing condition). These could vary depending upon the nature of any instream habitat improvements in the channel and the vegetation to be planted on the graded areas. I shall be here through Friday, but I will be out next week. If you anticipate needing our services before I return, let me know and I can brief someone else here on the model and the project. Happy Modeling, Bob The following is an attached File item from cc:Mail. It contains eight bit information which had to be encoded to insure successful trans- mission through various mail systems. To decode the file use the UUDECODE program. --------------------------------- Cut Here --------------------------------- Received: from eskinews.eskimo.com by paris.fabrik.com with ESMTP (Fabrik F07.1-000) id SINN.4847215@paris.fabrik.com ; Wed, 17 Sep 1997 16:09:14 -0700 Received: (from uucp@localhost) by eskinews.eskimo.com (8.8.7/8.8.5) with UUCP id PAA27184; Wed, 17 Sep 1997 15:58:01 -0700 Received: from cc:Mail by nhc.nhc-sea.com id AA874536188 Wed, 17 Sep 97 15:43:08 Date: Wed, 17 Sep 97 15:43:08 From: "Bob Elliot" <bElliot@nhc-sea.com> Message-Id: <9708178745.AA874536188@nhc.nhc-sea.com> To: jensen@entranco.com, swoodbury@ci.renton.wa.us Subject: HEC-RAS Page 2 Springbrook Creek, Renton Washington Oakesdale Project 9/17/97 U/S SW 16th Street 035 Legend 16 5 WS Exis LU Exis Ch L, Ground "t ' Ineff n 14 Bank Sta i 12 10 .16 8 a� w 6- 4- 2- 0 0 50 100 150 260 Station (ft) 1 in Horiz. =30 ft 1 in Vert. =3 ft Springbrook Creek, Renton Washington Oakesdale Project 9/17/97 SCS 1 location,channel improvement —.05 --.035--*.05 T .075 G , Legend 16 WS Exis LU Exis Ch Ground • 14 Bank Sta 12 10 c 0 > 8 w 6 4 2 0 100 150 200 T� 250— T— Station(ft) 1 in Horiz. =30 ft 1 in Vert. =3 ft Springbrook Creek, Renton Washington Oakesdale Project 9/17/97 Entranco DTM(664+40),channel improvement .05 .035 .05- egen 16 WS Exis LU Exis Ch ■ Ground • Bank Sta 14 12 10 C 0 co � $ 1 LU 6 4- 2- 0 ---T � 50 100 150 200 250 Station(ft) 1 in Horiz. =30 ft 1 in Vert. =3 ft Springbrook Creek, Renton Washington Oakesdale Project 9/17/97 Entranco DTM (663+90), channel improvement .05 )k .035 >!.( .05 /2 S (pO 21� Legend 16 WS Exis LU Exis Ch ■ Ground • Bank Sta 14 12 ' % 10 c 0 a� 8 w 6 4 2 0 50T� 100 150 200 Station (ft) 1 in Horiz. =30 ft 1 in Vert. =3 ft Springbrook Creek, Renton Washington Oakesdale Project 9/17/97 Entranco DTM(662+60),channel improvement 05---- -- ---vk<- .035 -- -.05 —� 16 Legend `L`j � l �� WS Exis LU Exis Ch Ground • Bank Sta 14 12 i 10] � 1 c 0 > 8 a� w 6 4-I 2- 0 0 50 100 150 200 Station(ft) 1 in Horiz.=30 ft 1 in Vert.=3 ft Springbrook Creek, Renton Washington Oakesdale Project 9/17/97 Entranco DTM(662+05), bridge opening .05 -.035—PI.05 Legend 16 h� (`; !_ WS Exis LU Exis Ch Ground • Bank Sta 14 12- 101 c 0 > 8 w 6 4 2 0 50 100 150 200 250 Station (ft) 1 in Horiz. =30 ft I in Vert. =3 ft Springbrook Creek, Renton Washington Oakesdale Project 9/17/97 Proposed Oakesdale Avenue Bridge � .05 r<- .035 -- ;_< -__ .05 _ - 'iLegend 16 WS Exis LU Exis Ch Ground • Bank Sta 14 12 10 c 0 > 8 a� LU 6- 4 2 0 50 100 150 200 250 Station(ft) 1 in Horiz. =30 ft 1 in Vert.=3 ft Springbrook Creek, Renton Washington Oakesdale Project 9/17/97 Proposed Oakesdale Avenue Bridge 05 035 05 egen 16 rro�L10 WS Exis LU Exis Ch Ground • Bank Sta 14-, 12 10 C O O $ j W 11 6 4 2- 0-1 - 50 160 150 200 250 Station(ft) 1 in Horiz. =30 ft 1 in Vert = 3 ft Springbrook Creek, Renton Washington Oakesdale Project 9/17/97 Entranco DTM(662+05), bridge opening .05 )k .035 )-k .05� Legend 16 WS Exis LU Exis Ch Ground • Bank Sta 14 12 10 c 0 > 8 a) w 6 4 2 0 50 100 150 200 250 Station (ft) 1 in Horiz. =30 ft 1 in Vert. =3 ft Springbrook Creek, Renton Washington Oakesdale Project 9/17/97 Entranco DTM (661+50). channel improvement .05 .035 > —.05 > e neg d 16 WS Exis LU Exis Ch I� �o Ground 14 Bank Sta 12 101 0 > 8 w 6 4 1 2 0-T-- 50 100 150 260 250 Station(ft) 1 in Horiz. =30 ft 1 in Vert. =3 ft Springbrook Creek, Renton Washington Oakesdale Project 9/17/97 Entranco DTM(659+95),channel improvement k .05 .035 .05 Legend 16 WS Exis LU Exis Ch Ground Bank Sta 14 12 10 C O > 8 N W 6 4 2 0 50 100 T- 150 200 250 Station(ft) 1 in Horiz. =30 ft 1 in Vert.=3 ft 10/23/97 13:20 FAX ENTRANCO ENG. 002/007 Post-its Fax Note 7671 Date �6f31/f7 pa°ges� To From Co./Dept. Co. Phone# Phone# MEMORANDUM Fax# 277- �' 7 Fax# J. Date: October 23, 1997 � ' To: Scott Woodbury From: Gregg Farris / Yl,{ ntid�ed � 54f � �� o y cc: Bruce Jensen, Peter DeBoldt ef-'y# Teo — fFG.y,en,�v� /JTw. 5�r�� *S !'evlse-A Subject: HEC-RAS Analysis of Springbrook Creek at Proposed Oakesdale Bridge A HEC-RAS analysis of Springbrook/Creek was%!performed to d ermine the effects of�t�e�A � proposed Oakesdale Bridge and the associated channel improvements upon the creek. The le- analysis was also used to support the design of channel stabilization improvements along the,- 1 ° banks of the creek. add or r- vu!) r-h"'"0A The proposed bridge is located roughly 300 feet upstream of the existing SW 16th Street ,A,, ru�c� Bridge within the City of Renton. Channel improvements are primarily located between the two bridges as well as immediately upstream of the proposed bridge. These improvements g�� generally involve widening the overbank portions of the creek and avoid altering the low-flow channel within the creek. All elevations in this analysis are referenced to the NGVD 1929 vertical datum. HEC-RAS MODEL The HEC-RAS model of Springbrook Creek used for this analysis was supplied by Northwest Hydraulics Consultants, Inc. (NHC). The model was originally created as a HEC-2 model by NHC in conjunction with RW Beck (NHC, 1996) and was subsequently converted into a HEC- RAS model specifically for this analysis. While an FEQ model of the creek was also available, the HEC-RAS model was chosen for this analysis since it is better suited to analyzing a variety of alternative scenarios than the FEQ model. The model extends from the Black River Pump Station (BRPS), which discharges into the Black River, upstream to SW 43rd Street, which represents the border between Renton and Kent. Three flow scenarios were input into the model, all of which were based on the 100-year flood event under a variety of assumed conditions. Both existing and future land use conditions throughout the basin were considered as well as the construction of improvements along the creek upstream of Oakesdale Bridge. The impact of the upstream channel improvements, once constructed, would be to increase peak flow rates at Oakesdale Bridge. 1 10/23/97 13:20 FAX ENTRANCO ENG. Z003/007 The specific flow rates for each scenario are listed in Table 1. These flow rates were generated by a combination of hydrologic and hydraulic models of the creek developed by NHC and RW Beck. The first model was developed using HSPF to perform a hydrologic analysis of the basin and to develop inflow hydrographs at specific locations along the creek. The HEC-2 model previously described was originally created to develop specific input (F-table) data for the HSPF model. The inflow hydrographs generated by HSPF were then input into an FEQ model of the creek. After routing these hydrographs through the creek, the peak 100-year flow rates generated by the FEQ model were used as the input flows for the HEC-RAS model used in this analysis. In general, the HEC-RAS results compared reasonably well with the FEQ results at many locations throughout the creek, though a direct comparison at the proposed bridge location could not be made. Table 1 Flow Scenarios Used in HEC-RAS Analysis 100-yr Flow at Downstream Flow Upstream Channel Oakesdale Boundary Water Scenario Land Use Improvements Bridge (cfs) Elevation (ft) 1 Existing Prior to Upstream Alt 3 934 4.1 Improvement (per NHC 1996) 2 Future Prior to Upstream Alt 3 1,106 4.1 Improvement (per NHC 1996) 3 Future After Upstream Alt 3 1,383 4.35 Improvement (per Renton 1997) The water surface elevations at the downstream boundary (i.e. the BRPS) for each flow scenario are also listed in Table 1. These elevations were generated by the FEQ analysis (RW Beck 1996), which was based on the pump station operation procedures. Under current procedures, the first of the larger pumps are manually turned on when the water surface at the pump station exceeds an elevation of approximately 4 feet, while additional pumps are added at 0.5-foot increments (see RW Beck 1996). The elevations in Table 1 represent an interpolated average. King County has the authority to completely shut down the pump station during extreme flood conditions in the Green River, forcing water to be stored in the creek upstream of the pump station. This scenario is described in further detail in the following bridge clearance discussion. In addition to the above flow scenarios, three geometry scenarios were developed for the HEC- RAS analysis related to the proposed Oakesdale Bridge improvements. These scenarios are listed in Table 2. Near the Oakesdale Bridge, the existing channel geometry is based on recent survey measurements and a digital terrain model created for the bridge project. The future channel geometry is based on the proposed channel improvements currently being designed for the bridge project. 2 10/23/97 13: 21 FAX ENTRANCO ENG. Z 004/007 66 v8 Table 2 �u ,fir Geometry Scenarios for HEC-RAS Analysis Within Study Reach 41v�. �� w, JIV, Channel Rau hness Geometry Channel Geometry Within Conditions Within Manning's n Manning's n in (I Scenario Study Reach Study Reach In channel overbanks c 1 Existing (before Existing Roughness 0.035 0.05 Oakesdale bridge/channel improvements) 2 Future (after Oakesdale Before plants well 0,0403 0,025' bridge/channel established improvements) 3 Future (after Oakesdale After plants well 0.040 0.090/0.075'.2 bridge/channel established improvements) 1, The only exception is beneath the bridge,where a value of 0.035 was used to repress rllpr p on each overbank 2. As directed by Scott Woodbury of Renton,0.090 was applied from the top of the low-fl annel up to an elevation of 7.0 feet (approximate 2-yr elevation)while 0,075 was applied above elevation 7.0 feet 3. Assumes that woody debris will be added to channel as a requlremeni for obtaining an HPA permit Different channel roughnesses were also considered for each scenario. Existing channel roughness values within the study reach were estimated in the original setup of the model based on observation rather than on calibration of the model. The overbank roughness values for the study reach are higher than the values used for the existing upstream reaches. Channel roughnesses immediately after construction of the Oakesdale improvements are assumed to be lower since the plants on the graded banks will not be well established. Once the plants become well established, then the roughness values will increase, as indicated in Table 2. For this scenario, roughness values were assumed to be 0.090 from the top of the low-flow channel up to an elevation of 7.0 feet, which is roughly equal to the 2-year water surface elevation. Above 7.0 feet, the roughness values were assumed to be 0.075. The difference in assumed roughness values above and below 7.0 feet reflects the difference in the type of vegetation proposed for the upper and lower regions of the channel banks. RESULTS OF HEC-RAS ANALYSIS The HEC-RAS model was used to analyze water surface elevations, velocities, and scour conditions that would result from the installation of the proposed Oakesdale Bridge and the associated channel improvements in Springbrook Creek. Water Surface Elevations Changes in the 100-year water surface elevations caused by the proposed bridge and channel improvements were estimated for both existing and future land use conditions (flow scenarios 1 and 2). In each case, widening of the overbank areas along Springbrook Creek near the proposed bridge resulted in a reduction of flood levels throughout this reach of the creek. Since flood levels are not increased at any location, this satisfies both local and federal floodplain management regulations. For existing land use conditions, the maximum reduction in 100-year 3 10i23/97 13: 21 FAX ENTRANCO ENG. Z 005/007 flood levels near the bridge was predicted to be approximately 0.3 feet, while for future land use conditions, the maximum reduction was approximately 0,4 feet. Table 3 summarizes the 100-year water surface elevations predicted by the HEC-RAS model at the upstream and downstream face of the proposed bridge for all three flow scenarios. These results assume that the vegetation on each bank has become well established (geometry scenario 3). Table 3 Predicted 100-Year Flood Elevations at Proposed Oakesdale Bridge Flow Flood Elevations at Flood Elevations at Scenario Upstream Face Downstream Face 1 8.3 8.2 2 8.8 8.7 3 9.7 9.6 Under the highest flow conditions (flow scenario 3), the 100-year flood elevations vary between 9.6 to 9.7 feet through the bridge. This is slightly higher than the elevation of the proposed walkway beneath the bridge, which is currently designed at an elevation of 9.0 feet. During the most extreme 100-year flow conditions, therefore, the proposed walkway could be inundated with up to 0,7 feet of floodwater. Bridge Clearance One of the design requirements for the bridge structure was that the design clearance must be a minimum of 2 feet per City of Renton requirements. The design clearance is defined as the vertical distance between the design water surface and the bottom of any part of the bridge (i.e. th low chord). Since the lowest part of the proposed Oakesdale Bridge is at an elevation of 16.0 et, the design water surface should be below 15.0 feet. As indicated in Table 3, the 100- (�'� ar flood elevation at the bridge is well below elevation 13.0 for each of the 100-year flow scenarios. These scenarios assume that the BRPS will not be required to reduce pumping rates due to high flow conditions in the Green River. If the pump rates at the BRPS must be reduced or completely shut off in accordance with the Green River Interlocal Agreement, then higher water levels will result as water is stored in the creek upstream of the pump station. The 100-year water surface elevation for this scenario was determined by the previous FEQ analysis to be 13.0 feet at the Oakesdale Bridge (RW Beck 1996). As a result, the bridge meets the required 2-foot clearance requirement even under this worst case scenario. Maximum Velocities The maximum velocities icrthe over b kf the creek channel were determined for the design of bank stabilization improvements' -_" - . Velocities were determined using the highest 100-year flow rate11 1 1 ow scenario 3) and assuming that the vegetation in the 4 10/23/97 13:22 FAX ENTRANCO ENG. Z 006/00 OJU �c 1., ScC ,✓v��j�" � overbanks beyond the b idge overpass had just been planted (geometry scenario 2) and were �\ well established (geom try scenario 3). Because overbank roughnesses are lower immediately after construction, the overbank velocities are higher than they would be after the plants ` become well establishe mmediately after construction, the peak velocities at the bridge are predicted to be rough) Y/ feet per second along each overbank. Once the plants become well established, peak ve ocities in the overbanks at the bridge would be slightly reduced.\ (A1l a+ ,; vP�•�rfy �u,. 061 rT �.e r�� 4/'i6Q , (��r ,.,_r z.ul �� Velocities in the Uin cha rnel of the creek were generally reduced following the install tion of the proposed bridge and channel improvements. Bridge Scour -� The HEC-RAS model was also used to predict bridge scour during the 100-year flood for the .3 proposed channel. The model predicted that the proposed channel alignment through the bridge would not cause any appreciable scouring conditions, as expected, even under the highest 100-year flow conditions (flow scenario 3). Contraction scour at the bridge would not be z expected since the overbanks through the bridge are slightly wider than the overbanks immediately upstream of the bridge. The bridge opening, therefore, does not represent a constriction to 100-year flows in the creek. Pier scour would not occur since no piers are being designed for the proposed bridge opening. Finally, abutment scour would be negligible since the abutments are located almost entirely outside of the 100-year floodplain. Under the most extreme 100-year flow conditions (flow scenario 3), flood levels would barely reach the vertical abutment and velocities would not be fast enough to cause any appreciable scouring conditions. j No scour analysis of the next downstream bridge at SW 16th Street was conducted, so it was Y not determined whether the channel improvements would affect scour conditions at this bridge. Summary of Results 455w-411 no �u�,�,� few,►�.t�� T! �1'!� 69,f31 ',- The results of the HEC-RA analysis indicate that the proposed bridge and channel improvements will reduce 100 ear flood levels up to a maximum of 0.3 to 0.4 feet through this reach of Springbrook Creek. The walkway beneath the bridge would not be inundated by the 100-year flood, except by the highest 100-year flow scenario (scenario 3), in which case the walkway would be inundated up to 0.7 feet. Requirements for minimum bridge clearance would also not be violated. , Maximum overbank velocities at the proposed bridge during the 100- ear flood will be higher immediately after construction than after the plants become well esta ished. Peak velocities in the left and right overbanks at the bridge are predicted to be roughly 3 feet per second, immediately after construction. Peak velocities in the main channel are predicted to be slightly lower than current peak velocities as a result of the proposed channel improvements. Finally, the model predicted that the proposed bridge and channel alignment will not produce any appreciable scouring conditions. 5 10/23/97 13:22 FAX ENTRANCO ENG. 2 007/007 roAt- �etek4 p q,,i 5) 41,�s f-,cic 5?gi BANK PROTECTION G S0u4, -0 Using the maximum overbank velocities predicted by the HEC-RAS de d the proposed bank slopes through the bridge, the required slope protection for each ank benea h the bridge was determined. Along the left bank (facing downstream), a peak velocity of ' feet per second in combination with a 3:1 slope would require a graded roc 'material with a median diameter of at least 3 inches. For the right bank, a peak velocity of feet per second along a 9:1 slope would require a graded material with a slightly smaller median diameter. While quarry spalls may work in this application, it is conservatively recommended that either light loose riprap OT be used to stabilize both banks beneath the bridge. Upstream and downstream of the bridge, all graded areap4iAn the channel and ove►banks of the creek should be covered to help prevent erosion. A,,o'�.�y be appropriate for this application. However, the specific type and placem nt of fabric should be coordinated with the proposed landscaping plan for these areas. REFERENCES l5 veGu� rAc 7 NHC, 1996. ESGRWP Hydrologic Analysis Final Report. March. King County, 1990. King County, Washington Surface Water Design Manual. King County Department of Public Works. January. Renton, 1997. ESGRWP Final Plan and EIS. September. RW Beck, 1996. ESGRWP Hydraulic Analysis Report, Existing Drainage System. March. 6 Sean S. Woodbury From: Gregg Farris To: Swoodbury Subject: Updated HEC-RAS model of Springbrook Creek Date: Wednesday, January 01, 1997 1:09PM < <File Attachment: PKUNZIP.EXE> > < <File Attachment: HEC-RAS.ZIP> > From: Gregg Farris Date: Thu, Oct 23, 1997 1:09 PM Subject: Updated HEC-RAS model of Springbrook Creek To: Swoodbury Scott, Attached is the revised HEC-RAS model of Springbrook Creek, which has all of your suggested revisions incorporated into the model. The updated technical memo will be faxed and mailed separately. If you have any questions about the model, please call me at 454-5600. Thanks. ([ HEC-RAS.ZIP : 3358 in HEC-RAS.ZIP ]][[ PKUNZIP.EXE : 3359 in PKUNZIP.EXE ]l The following binary file has been uuencoded to ensure successful transmission. Use UUDECODE to extract. The following binary file has been uuencoded to ensure successful transmission. Use UUDECODE to extract. Received: from dns2.seanet.com by paris.fabrik.com with SMTP (Fabrik F07.1-000) id SINN.5415357@paris.fabrik.com ; Thu, 23 Oct 1997 13:24:48 -0700 Received: from entranc01 .seanet.com (entranc01 .seanet.com [199.181.165.229]) by mx.seanet.com (8.8.5/Seanet-8.7.3) with SMTP id NAA17185 for <swoodbury@ci.renton.wa.us>; Thu, 23 Oct 1997 13:19:15 -0700 (PDT) Received: by entranc01.seanet.com with Microsoft Mail id <344FBOF3@entranc01.seanet.com>; Thu, 23 Oct 97 13:17:55 PDT From: Gregg Farris <farris@entranco.com> To: "Scott Woodbury @ Renton" <swoodbury@ci.renton.wa.us> Subject: Updated HEC-RAS model of Springbrook Creek Date: Thu, 23 Oct 97 13:09:00 PDT Message-ID: <344FBOF3@entranc01.seanet.com> Encoding: 10 TEXT, 10106 UUENCODE, 659 UUENCODE X-Mailer: Microsoft Mail V3.0 X-MS-Attachment: HEC-RAS.ZIP 454487 10-23-1997 13:05 X-MS-Attachment: PKUNZIP.EXE 29378 02-01-1993 02:04 Page 1 10/23/97 13:19 FAX ENTRANCO ENG. Z 001/007 E N T R A N C C ENGINEERS• SCIENTISTS. PLANNERS• SURVEYORS 10900 NE 8th Street.Suite 300 (206)454.5600 Bellevue,Washington 98004 Fax No. (425)454.0220 FACSIMILE TRANSMITTAL Date October 23, 1997 PLEASE DELIVER THE FOLLOWING PAGES IMMEDIATELY TO: Name Scott Woodbury Firm/Agency City of Renton City Renton Fax Number 235-2541 From Gregg Farris Project/Promo Name Oakesdale Bridge Project/Promo No. 97027-21 Remarks/Items Transmitted: Scott, Attached is the revised HEC-RAS technical memorandum for the Oakesdale Bridge project. All of your suggested model revisions were incorporated into the model representing the proposed bridge improvements. Some of these changes were also incorporated into to the model representing the bridge improvements immediately after construction. After running the updated hydraulic models, the technical memorandum was updated to reflect these new results. I will mail an original copy of the technical memorandum to you and e-mail the latest version of the HEC-RAS model to you as well. If you have any questions, please feel free to call me. Thank you. Gregg Hard Copy ❑x Will Will Not Be Sent No. of Pages (Including Transmittal Sheet) 7 If there are problems with transmission, call Gregg (425) 454-5600 The information in this fax is confidential and proprietary and is intended only for the individual or entity named on the cover sheet. If you are not the intended recipient, disclosure, copying, distribution or use of this information is prohibited. If you do not receive all of the pages or have received this fax in error, please notify us immediately at the above telephone number. S:IENVAa300g•781oui maINWSDFWN:1,0cc 09/30/97 14:30 FAX ENTRANCO ENG. ?001/006 4ME N T R A N C O ENGINEERS* SCIENTISTS- PLANNERS* SURVEYORS 10900 NE 8th Street.Suite 300 (206)454-5600 Bellevue,Washington 98004 Fax No.(425)454.0220 FACSIMILE TRANSMITTAL Date September 30, 1997 PLEASE DELIVER THE FOLLOWING PAGES IMMEDIATELY TO: Name Scott Woodbury Firm/Agency City of Renton City Renton Fax Number 235-2541 From Gregg Farris Project/Promo Name Oaksdale Bridge Project/Promo No. 97027-21 Remarks/Items Transmitted: Scott, Attached is the technical memorandum summarizing the results of the HEC-RAS analysis for the Oaksdale Bridge project. I will attempt to zip the HEC-RAS files and e-mail them to you, so let me know if you don't receive them. If you have any questions, please feel free to call me. Thank you. Gregg Hard Copy Will ❑x Will Not Be Sent No. of Pages (Including Transmittal Sheet) 6 If there are problems with transmission,call Gregg (425) 454-5600 The information in this fax is confidential and proprietary and is intended only for the individual or entity named on the cover sheet. If you are not the intended recipient, disclosure, copying, distribution or use of this information is prohibited_ If you do not receive all of the pages or have received this fax in error, please notify us immediately at the above telephone number. 5:4ENVW5008.781out_maIRW SOFwf=1.u oc 09/30/97 14:30 FAX ENTRANCO ENG. 1j002/006 MEMORANDUM Date: September 30, 1997 To: Scott Woodbury From: Gregg Farris cc: Bruce Jensen, Peter DeBoldt alce Sd�t Subject: HEC-RAS Analysis of Springbrook Creek at Propose¢Oaksda e_8ridge A HEC-RAS analysis of Springbrook Creek was performed to determine the effects of the proposed Oaksdale Bridge and the associated channel improvements upon the creek. The analysis was also used to support the design of channel stabilization improvements along the banks of the creek. The proposed bridge is located roughly 300 feet upstream of the existing SW 16th Street Bridge within the City of Renton. Channel improvements are primarily located between the two bridges as well as immediately upstream of the proposed bridge. These improvements generally involve widening the overbank portions of the creek and avoid altering the low-flow channel within the creek. /�!/ elev ?iw) rn ��S G.a6ySAS Are- !ri he NGvo Y72 HEC-RAS MODEL The HEC-RAS model of Springbrook Creek used for this analysis was supplied by Northwest Hydraulics Consultants, Inc. (NHC). The model was originally created as a HEC-2 model by NHC in conjunction with RW Beck (NHC, 1996) and was subsequently converted into a HEC- RAS model. The model extends from the Black River Pump Station (BRPS), which discharges into the Black River, upstream to SW 43rd Street, which represents the border between Renton and Kent. Three flow scenarios were input into the model, all of which were based on the 100-year flood event under a variety of assumed conditions. Both existing and future land use conditions throughout the basin were considered as well as the construction of improvements along the creek upstream of Oaksdale Bridge. The impact of the upstream channel improvements, once constructed, would be to increase peak flow rates at Oaksdale Bridge. \� "stf The specific flow rates for each scenario are fisted in Table 1. These flow rates were generated d by two additional models of the creek developed by NHC and RW Beck. The first model was developed using HSPF to perform a hydrologic analysis of the basin and to develop inflow do hydrographs at specific locations along the creek. Theme inflow hydrographs were then input �S6�{in into an FEQ model of the creek. After routing the a hydrographs through the creek, the peak f� v �,,, 1a5 i, , 1r itC I I ��J 09/30/97 14:30 FAX ENTRANCO ENG. Z 003/006 kil- m 100-year flow rates generated by the FEG model were used as the input flows for the HEC- r��ti �� RAS model. `LL Table 1 Flow Scenarios Used In HEC-RAS Analysis U 100-yr Flow at Downstream Flow Upstream Channel Oaksdale Boundary Water Scenario Land Use Improvements Bridge (cfs) Elevation (ft) �J k° � 1 Existing B i ) ✓ 934 4.1 i/c 11K 2 Future �er 1,106 4.1 14c 1 ay 3 Future Afte tture) ,� j, All 1,11383 4.35 The water surface elevations at the downstream boundary (i.e. Oe BRPS) for each flow arc .,,.. >;,¢ rGt '; a �� - s enario are also listed-in-Table 1. These elevat' s were �e�Foxfmated tr+ I ,q f S tax©ds based on th `�'. `f 0i pump station ' e"� " b iu d gyG operated. Under current procedures, the larger pumps a4 manually turned on when the water ge,,k surface at the pump station exceeds an elevation of approximately 4 feet. 44�e King County has the authority to completely shut down the pump station during extre a flood conditions in the Green River .ems Fed a� �t�:v+a� � pt •rre ate) — �, r fie le sr� �,p 9r�•n � 7.1j-+.1 ;�crcra-l-J. cc �9�� S�4fl 1S. i.ra' 7� cdL e.^.�,r� fA- .l c/eer�Fnce q .rerc to alditlon to the move flow scenario, three geometry scenarios were develo ed for the HEC- RAS analysis related to the proposed Oaksdale Bridge improvements. Th,6se scenarios are listed in Table 2. Near the Oaksdale Bridge, the existing channel geometry is based on recent survey measurements and a digital terrain model created for the bridge project. The future Si ►wi�w�l�N 0 channel geometry is based on the proposed channel improvements qurrently being designed J,s5w'mllm for the bridge project. -�cis 01COW4�anS �n �°►6le I bvV�. Table 2 Geometry Scenarios Used In HEC-RAS Analysis Geometry Channel Roughness Manning's n Manning's n Scenario / w Ch nnel Geometry Conditions in channel in overbanks up14,ro At Tip s r� ! 0.05�0 1 Existing (before Oak�Pc�ale 9xisting Roughness 0.035 improvements) 2 Future (after Oaksdale Before plants well 0,040 0.0251 improvements) established 3 Future (after Oaksdale After plants well 0.040 0.075''2 > improvements) established 1. The only exception is beneath the bridge,where a value of 0.035 was used to represent riiprap on each overbank 2. 0.075 was only applied above an elevation of 7.0 feel(approximate 2-/yr elevation)per discussion with Scott Woodbury �SSkwv..�S �vOFw G/t1fX �uri'e Grivu�y e��,s 6-c. aaf.�c� /�, � r� �s' ry•rlic�w-hdr �vr �Frr/v�"s� 4n �dP/4 �.Psy.,,} rrn/ �� � �f� . 2 09/30/97 14:31 FAX ENM-INCO G. � S�.rur'"' �004/006 JLA Of Different channel. roughnesses were also considered for each scenario. Existing channel roughness values'were estimated in the original setup of the model based on observation rather than on calibration of the model. Channel roughnesses immediately after construction of the Oaksdale improvements are assumed to be lower since the plants on the graded banks will not be well established. Once the plants become well established, then the roughness values will increase, as indicated in Table 2. Roughness values were assumed to primarily increase above the 2-year water surface elevation, which is roughly at an elevation of 7.0 feet. RESULTS OF HEC-RAS ANALYSIS The HEC-RAS model was used to analyze water surface elevations, velocities, and scour conditions that would result from the installation of the proposed Oaksdale Bridge and the associated channel improvements in Springbrook Creek. Water Surface Elevations Changes in the 100-year water surface elevations caused by the proposed bridge and channel improvements were estimated for both existing and future land use conditions (flow scenarios 1 and 2). In each case, widening of the overbank areas along Springbrook Creek near the proposed bridge resulted in a reduction of flood levels throughout this reach of the creek. Since flood levels are not increased at any location, this satisfies both local and federal floodplain management regulations. For existing land use conditions, the maximum reduction in 100-year flood levels near the bridge was predicted to be approximately 0.5 feet, while for future land use conditions, the maximum reduction was approximately 0.6 feet. Table 3 summarizes the 100-year water surface elevations predicted by the HEC-RAS model at the upstream and downstream face of the proposed bridge for all three flow scenarios. These results assume that the vegetation on each bank has become well established (geometry scenario 3). Table 3 Predicted 100-Year Flood Elevations at Proposed Oaksdale Bridge Flow Flood Elevations at Flood Elevations at Scenario Upstream Face Downstream Face 1 8.1 7.9 2 8.6 8.3 3 9.4 9.1 Under the highest flow conditions (flow scenario 3), the 100-year flood elevations vary between 9.1 to 9.4 feet through the bridge. This is slightly higher than the elevation of the proposed walkway beneath the bridge, which is currently designed at an elevation of 9.0 feet. During the most extreme 100-year flow conditions, therefore, the proposed walkway could be inundated with up to 0.4 feet of floodwater. 3 09/30/97 14:31 FAX ENTRaNCO ENG. 005/006 rs re �� Gg�"re loo--10(" (low o One of the des' requi ments for thre bridge structure was that the design clearance must be a minimum of 3 feet. The design clearance is defined as the vertical distance between the design water surface and the bottom of any part of the bridge (i.e. the low chord). Since the lowest part of the proposed Oaksdale Bridge is at an elevation of feet, the design water surface should be below 13.0 feet. As indicated in Table 3, the 100-year flood elevation at the bridge is well below elevation 13.0 for each of the 100-year flow scenarios. In fact, the current bridge configuration even satisfies the more stringient King County requirements in which the design clearance must be a minimum of 6 feet for Type 1 streams (King County 1990). 7&r ��s Maximum Velocities �e / � w �� �� � ������ ph ,i� �e�)S� me 9 F/wA C', =M; 6"fe+ Rwer CACCad'k,.ee wltk 2tv� /„h/���e.( /a �ee,.,.e, r/�-4,7 A:14&- The maximum velocities in the overbanks of the creek channel were determinedlor the design(,„.4-&� of bank stabilization improvements beneath the proposed bridge. Velocities were determined / •�r using the highest 100-year flow rate (flow scenario 3) and assuming that the vegetation in the- 9 re4.ff overbanks beyond the bridge overpass had just been planted (geometry scenario 2) and were I's W*kcr well established (geometry scenario 3). Because overbank roughnesses are lower immediately; J rcCd after construction, the overbank velocities are higher than they would be after the plants ,,,,, J. become well established. Immediately after construction, the peak velocities in the left and right . a overbanks at the bridge are predicted to be roughly 3'/2 and 4'/2 feet per second, respectively. Once the plants become well established, peak velocities would be reduced to roughly 2 /2 and 3 feet per second, respectively, in the left and right overbanks. P 01" . Velocities in the main channel of the creek were generally reduced following the installation of die lcv-, ee., the proposed bridge and channel improvements. a ,, �f, �� f �c D es ik / J� s /3.o ro 1..r,,�n5(4,g4��•7-/u-s 7-� Bridge Scour bd / '+Pt �i✓"'1 rF7I '� ~s f"0/ C C/W�/ Sll.La�l4N� The HEC-RAS model was also used to predict bridge scour dunngWe 100-year flood for the proposed channel. The model predicted that the proposed channel alignment through the bridge would not cause any appreciable scouring conditions, as expected, even under the highest 100-year flow conditions (flow scenario 3). Contraction scour at the bridge would not be expected since the overbanks through the bridge are slightly wider than the overbanks immediately upstream of the bridge. The bridge opening, therefore, does not represent a constriction to 100-year flows in the creek. Pier scour would not occur since no piers are being designed for the proposed bridge opening. Finally, abutment scour would be negligible since the abutments are located almost entirely outside of the 100-year floodplain. Under the most extreme 100-year flow conditions (flow scenario 3), flood levels would barely reach the vertical abutment and velocities would not be fast enough to cause any appreciable scouring conditions. No scour analysis of the next downstream bridge at SW 16th Street was conducted, so it was not determined whether the channel improvements would affect scour conditions at this bridge. Summary of Results The results of the HEC-RAS analysis indicate that the proposed bridge and channel improvements will reduce 100-year flood levels up to a maximum of 0.5 to 0.6 feet through this reach of Springbrook Creek. The walkway beneath the bridge would not be inundated by the 100-year flood, except by the highest 100-year flow scenario (scenario 3), in which case the walkway would be inundated up to 0.4 feet. Requirements for minimum bridge clearance would also not be violated . 4 09/30/97 14:32 FAX ENTRANCO ENG. Z 006/006 Maximum overbank velocities at the proposed bridge during the 100-year flood will be higher immediately after construction than after the plants become well established. Peak velocities in the left and right overbanks at the bridge are predicted to be roughly 3'/2 and 4'/2 feet per second, respectively, immediately after construction. Peak velocities in the main channel are predicted to be slightly lower than current peak velocities as a result of the proposed channel improvements. Finally, the model predicted that the proposed bridge and channel alignment will not produce any appreciable scouring conditions. BANK PROTECTION Using the maximum overbank velocities predicted by the HEC-RAS model and the proposed bank slopes through the bridge, the required slope protection for each bank beneath the bridge was determined. Along the left bank (facing downstream), a peak velocity of 3'/2 feet per second in combination with a 3:1 slope would require a graded rock material with a median diameter of at least 3 inches. For the right bank, a peak velocity of 4'/2 feet per second along a 9:1 slope would require a graded material with a median diameter of at least 4 inches. While quarry spalis may work in this application, it is conservatively recommended that light loose riprap be used to stabilize both banks beneath the bridge. LAID /S 1,eea,,,,ffj-,Jej REFERENCES NHC, 1996. ESGRWP Hydrologic Analysis Final Report. March.t9a6. King County, 1990. King County, Washington Surface Water Design Manual. King County Department of Public Works. Januar)4i9Q0' Cr �� A-'�.r/ 199-7. F-sC.ltwp F,,( /'�•,, a.�l f�S. 5�. 6cr. 14 i6 SG Jm day of'ir�i•,�i c .4,)., 5 ,F,^,'A/7 CO legu/f 5 /�c� -Z � /�iad�S.� �/I� �SQ� l�(l�°t 7 �/U.,Svr,i+�.l �r � �d f.S �� Gt�f�•-„S' tX HEC-RAS River:Springbrook Cr Reach:BRPS to 43rd !h All ll .ViO V/)-C S i8a Profile'= Plar ;R � S Bridge II Exis LU Exis Ch �';_ 935.00 0.24 7.58 3.89 7.69 0.000428 2.76 338.43 59.97 0.20 Exis LU Exis Ch 935.00 0.24 7.58 3.89 7.69 0.000428 2.76 338.43 59.97 0.20 ` - Futr LU AIt3 Ch 1389.00 0.24 8.86 4.48 9.04 0.000477 3.34 415.60 59.99 0.22 tp Exs LU Exis Ch 934.00 1.65 7.55 7.77 0.002301 3.79 246.42 70.74 0.36 Exis LU Exis Ch 934.00 1.65 7.37 7.97 0.010088 6.22 150.18 45.22 0.60 B,f� s t�.F „ i utt�J AIt3 Ch 1383.00 1.65 8.85 9.11 0.002071 4.05 341.09 74.86 0.33 B 43975 Exis LU Exis Ch 934.00 1.70 7.59 7.89 0.001912 4.88 229.79 62.07 0.37 BRPS to 43r + 6975 Exis LU Exis Ch ;:• 934.00 1.70 7.65 8.36 0.006236 6.83 147.06 34.93 0.52 BRPSo 43rd ��5876 Futr `LU Alta Ch 1383.00 1.70 8.87 9.22 0.001723 5.33 312.06 66.51 0.36 BRPS 43rd #325 Exis LU Exis Ch 934.00 1.70 7.70 7.98 0.001643 4.64 238.57 67.14 0.34 BRPS= 43rd ''6025 Exis LU Exis Ch 934.00 1.60 8.08 8.53 0.001739 5.47 186.62 37.34 0.39 BRPS: -:43rd 6025 Futr LU AIt3 Ch ° 1383.00 1.70 8.99 9.30 0.001462 5.02 329.11 72.95 0.34 BRPS to 43rd 6155 Exis LU Ews Ch 934.00 1.00 7.94 8.17 0.001253 4.21 267.48 80.96 0.29 BRPS to 43rd 6155 ;Exis LU E7usClt 934.00 1.00 8.42 8.71 0.000961 4.38 225.83 40.59 0.30 BRPS to 43rd 6155 Futr LU Aft3Ch,nNI 1383.00 1.00 9.22 9.47 0.001162 4.58 378.85 92.43 0.29 BRPS to 43rd 6156 Exis LU Exis:Gh 934.00 0.80 7.94 8.17 0.001131 4.09 266.18 74.18 0.28 BRPS to 43rd 6156 Futr LU h t 1383.00 0.80 9.21 9.48 0.001125 4.59 371.61 98.00 0.29 h a BRPS to 43rd 6210 : Bridge «...., .BRPS to 43rd 6264 EIms't_U EIfISCh ,,,; 934.00 0.80 8.08 4.58 8.29 0.001033 3.96 276.24 76.01 0.27 BRPS to 43rd 67.64 Futr Ll3 ,F#� h 1383.00 0.80 9.35 5.72 9.60 0.001023 4.43 385.18 98.00 0.28 imiy (BRPS to 43rd 6265 ��.It Tas Ch Pta1t: . 934.00 0.70 8.11 8.29 0.000757 3.52 285.49 57.23 0.24 6RPS to 43rd 6265 U Exis Gh PIS+ 934.00 0.70 8.61 8.80 0.000550 3.54 280.00 47.66 0.23 BRPS to 43rd 6265 !�A)t ChEt;''„ Plan 02?` 1383.00 0.70 9.34 9.60 0.000901 4.29 364.47 78.87 0.27 BRPS to 434 ``'6420 AS Gh Plan 07y 934.00 0.80 8.19 8.48 0.001326 4.51 231.94 52.57 0.31 BRPS to 43rd 6420 „Exis Ch Fl�r U1 934.00 0.80 8.64 8.95 0.000972 4.51 232.81 45.88 0.30 BRPS to 43rd 642i[t3 Ch n 02 1383.00 0.80 9.43 9.82 0.001460 5.31 299.89 57.07 0.34 © E N T R A N C O 10900 NE 8TH STREET,SUITE 300 (425)454-5600 BELLEVUE,WASHINGTON 98004 FAX(425)454-0220 LETTER OF x TRANSMITTAL ❑ MEMORANDUM To: City of Renton Date: 11/12/97 Dept. of Planning/Building/Public Works Fourth Floor 200 Mill Avenue S Project No.: 197027-21 Renton, WA 98055-2189 Title: Oakesdale Bridge Attention: Scott Woodbury Re: Updated HEC-RAS Memo X ATTACHED ❑ ORIGINALS ❑ UNDER SEPARATE COVER ❑ PRINTS ❑OTHER FOR YOUR: ® INFORMATION/USE ® AS REQUESTED OTHER OUR ACTION: ❑ REVIEWED ❑ NOT APPROVED ❑ APPROVED ❑ SEE REMARKS REQUESTED ACTION: ❑ APPROVAL ❑ REVIEW&COMMENT ❑ MAKE CORRECTIONS NOTED ❑ REVISE AND RESUBMIT ❑OTHER NO.OF DRAWING COPIES NUMBER DESCRIPTION 1 Updated technical memorandum summarizing Oakesdale Bridge HEC- RAS Analysis Remarks: If you have any questions or comments, please give me a call at 454-5600. By: Gregg Farris cc: Ralph Nelson DISTRIBUTION: WHITE TO ADDRESSEE CANARY TO PROJECT FILE A02_LOT(rev.6/97) PINK TO DAY FILE 430 MEMORANDUM Date: November 12, 1997 To: Scott Woodbury From: Gregg Farris cc: Bruce Jensen, Peter DeBoldt Subject: HEC-RAS Analysis of Springbrook Creek at Proposed Oakesdale Bridge A HEC-RAS analysis of Springbrook Creek was performed to determine the effects of the proposed Oakesdale Bridge and the associated channel improvements upon the creek. The analysis was also used to support the design of channel stabilization improvements along the banks of the creek. The proposed bridge is located roughly 300 feet upstream of the existing SW 16th Street Bridge within the City of Renton. Channel improvements are primarily located between the two bridges as well as immediately upstream of the proposed bridge. These improvements generally involve widening the overbank portions of the creek and avoid altering the low-flow channel within the creek. All elevations in this analysis are referenced to the NGVD 1929 vertical datum. HEC-RAS MODEL The HEC-RAS model of Springbrook Creek used for this analysis was supplied by Northwest Hydraulics Consultants, Inc. (NHC). The model was originally created as a HEC-2 model by NHC in conjunction with RW Beck (NHC, 1996) and was subsequently converted into a HEC- RAS model specifically for this analysis. While an FEQ model of the creek was also available, the HEC-RAS model was chosen for this analysis since it is better suited to analyzing a variety of alternative scenarios than the FEQ model. The model extends from the Black River Pump Station (BRPS), which discharges into the Black River, upstream to SW 43rd Street, which represents the border between Renton and Kent. Three flow scenarios were input into the model, all of which were based on the 100-year flood event under a variety of assumed conditions. Both existing and future land use conditions throughout the basin were considered as well as the construction of improvements along the creek upstream of Oakesdale Bridge. The impact of the upstream channel improvements, once constructed, would be to increase peak flow rates at Oakesdale Bridge. 1 The specific flow rates for each scenario are listed in Table 1. These flow rates were generated by a combination of hydrologic and hydraulic models of the creek developed by NHC and RW Beck. The first model was developed using HSPF to perform a hydrologic analysis of the basin and to develop inflow hydrographs at specific locations along the creek. The HEC-2 model previously described was originally created to develop specific input (F-table) data for the HSPF model. The inflow hydrographs generated by HSPF were then input into an FEQ model of the creek. After routing these hydrographs through the creek, the peak 100-year flow rates generated by the FEQ model were used as the input flows for the HEC-RAS model used in this analysis. In general, the HEC-RAS results compared reasonably well with the FEQ results at many locations throughout the creek, though a direct comparison at the proposed bridge location could not be made. Table 1 Flow Scenarios Used in HEC-RAS Analysis 100-yr Flow at Downstream Flow Upstream Channel Oakesdale Boundary Water Scenario Land Use Improvements Bridge (cfs) Elevation (ft) 1 Existing Prior to Upstream Alt 3 934 4.1 Improvement (per NHC 1996) 2 Future Prior to Upstream Alt 3 1,106 4.1 Improvement (per NHC 1996) 3 Future After Upstream Alt 3 1,383 4.35 Improvement (per Renton 1997) The water surface elevations at the downstream boundary (i.e. the BRPS) for each flow scenario are also listed in Table 1. These elevations were generated by the FEQ analysis (RW Beck 1996), which was based on the pump station operation procedures. Under current procedures, the first of the larger pumps are manually turned on when the water surface at the pump station exceeds an elevation of approximately 4 feet, while additional pumps are added at 0.5-foot increments (see RW Beck 1996). The elevations in Table 1 represent an interpolated average. King County has the authority to completely shut down the pump station during extreme flood conditions in the Green River, forcing water to be stored in the creek upstream of the pump station. This scenario is described in further detail in the following bridge clearance discussion. In addition to the above flow scenarios, three geometry scenarios were developed for the HEC- RAS analysis related to the proposed Oakesdale Bridge improvements. These scenarios are listed in Table 2. Near the Oakesdale Bridge, the existing channel geometry is based on recent survey measurements and a digital terrain model created for the bridge project. The future channel geometry is based on the proposed channel improvements currently being designed for the bridge project. 2 Table 2 Geometry Scenarios for HEC-RAS Analysis Within Study Reach Channel Roughness Geometry Channel Geometry Within Conditions Within Manning's n Manning's n in Scenario Study Reach Study Reach in channel overbanks 1 Existing (before Existing Roughness 0.035 0.050/0.075 Oakesdale bridge/channel improvements) 2 Future (after Oakesdale After plants well 0.0403 0.090/0.07512 bridge/channel established improvements) 3 Future (after Oakesdale Before plants well 0.0403 0.025' bridge/channel established improvements) 1. The only exception is beneath the bridge,where a value of 0.035 was used to represent riprap on each overbank 2. As directed by Scott Woodbury of Renton,0.090 was applied from the top of the low-flow channel up to an elevation of 7.0 feet (approximate 2-yr elevation)while 0.075 was applied above elevation 7.0 feet 3. Assumes that woody debris will be added to channel as a requirement for obtaining an HPA permit Different channel roughnesses were also considered for each scenario. Existing channel roughness values within the study reach were estimated in the original setup of the model based on observation rather than on calibration of the model. The overbank roughness values for the study reach are higher than the values used for the existing upstream reaches. Channel roughnesses immediately after construction of the Oakesdale improvements are assumed to be lower since the plants on the graded banks will not be well established. Once the plants become well established, then the roughness values will increase, as indicated in Table 2. For this scenario, roughness values were assumed to be 0.090 from the top of the low-flow channel up to an elevation of 7.0 feet, which is roughly equal to the 2-year water surface elevation. Above 7.0 feet, the roughness values were assumed to be 0.075. The difference in assumed roughness values above and below 7.0 feet reflects the difference in the type of vegetation proposed for the upper and lower regions of the channel banks. RESULTS OF HEC-RAS ANALYSIS The HEC-RAS model was used to analyze water surface elevations, velocities, and scour conditions that would result from the installation of the proposed Oakesdale Bridge and the associated channel improvements in Springbrook Creek. Water Surface Elevations Changes in the 100-year water surface elevations caused by the proposed bridge and channel improvements were estimated for both existing and future land use conditions (flow scenarios 1 and 2). In each case, widening of the overbank areas along Springbrook Creek near the proposed bridge resulted in a reduction of flood levels throughout this reach of the creek. Since flood levels are not increased at any location, this satisfies both local and federal floodplain management regulations. For existing land use conditions, the maximum reduction in 100-year 3 flood levels near the bridge was predicted to be approximately 0.2 feet, while for future land use conditions, the maximum reduction was approximately 0.25 feet. Table 3 summarizes the 100-year water surface elevations predicted by the HEC-RAS model at the location of the upstream face of the proposed bridge for all three flow and geometry scenarios. Table 3 Predicted 100-Year Flood Elevations at the Location of the Proposed Oakesdale Bridge Upstream Face Flow Geometry Scenario Scenario 1 2 3 1 8.54 8.34 8.04 2 9.07 8.82 8.49 3 --- 9.68 9.25 Under the highest flow conditions (flow scenario 3 & geometry scenario 2), the 100-year flood elevations vary between 9.6 to 9.7 feet through the bridge. This is slightly higher than the elevation of the proposed walkway beneath the bridge, which is currently designed at an elevation of 9.0 feet. During the most extreme 100-year flow conditions, therefore, the proposed walkway could be inundated with up to 0.7 feet of floodwater. Bridge Clearance One of the design requirements for the bridge structure was that the design clearance must be a minimum of 2 feet per City of Renton requirements. The design clearance is defined as the vertical distance between the design water surface and the bottom of any part of the bridge (i.e. the low chord). Since the lowest part of the proposed Oakesdale Bridge is currently designed at an elevation of 14.9 feet, the design water surface should be below 12.9 feet. As indicated in Table 3, the 100-year flood elevation at the bridge is well below elevation 12.9 feet for each of the 100-year flow scenarios. These scenarios assume that the BRPS will not be required to reduce pumping rates due to high flow conditions in the Green River. If the pump rates at the BRPS must be reduced or completely shut off in accordance with the Green River Interlocal Agreement, then higher flood levels will result as water is stored in the creek upstream of the pump station. The 100-year water surface elevation for this scenario was determined by the previous FEQ analysis to be 13.0 feet at the Oakesdale Bridge (RW Beck 1996), which resulted in a bridge clearance of 1.9 feet. However, this clearance was considered acceptible since it would only occur on the downstream face of the proposed bridge and would only span a distance of less than 10 feet. Over the entire span of the downstream face, which is roughly 140 feet, the low chord rises from an elevation of 14.9 feet to 17.7 feet. Therefore, except for this short distance over which the low chord of the downstream face barely drops below an elevation of 15.0 feet, the bridge meets the required 2-foot clearance requirement even under this worst case scenario. 4 Maximum Velocities The maximum velocities along the overbanks of the creek channel were determined for the design of bank stabilization improvements beneath the proposed bridge. Velocities were determined using the existing 100-year flow rate (flow scenario 1) in combination with channel conditions immediately after construction (geometry scenario 3) as well as using future 100- year flow rates (flow scenario 3) in combination with channel conditions after the overbank plants had become well established (geometry scenario 2). Because overbank roughnesses directly beneath the bridge will be the same immediately after construction as under future flow conditions, due to the proposed use of rock for slope protection under the bridge, the overbank velocities produced by the future flow conditions (flow scenario 3) will be higher. Immediately after construction, the peak velocities beneath the bridge along the left and right overbanks are predicted to be roughly 3 and 2 feet per second, respectively. Future peak velocities in the left and right overbanks are predicted to be roughly 31/2 and 3 feet per second, respectively. Upstream and downstream of the bridge, peak overbank velocities were predicted to be higher immediately after construction than after the plants become well established under future flows. Immediately after construction, when overbank roughnesses are lower, peak overbank velocities ranged from roughly 2 to 41/2 feet per second. Under future conditions, peak overbank velocities were reduced to between roughly 1 to 31/2 feet per second. Velocities in the main channel of the creek were generally reduced following the installation of the proposed bridge and channel improvements. Bridge Scour The HEC-RAS model was also used to predict bridge scour during the 100-year flood for the proposed channel. The model predicted that the proposed channel alignment through the bridge would not cause any appreciable scouring conditions, as expected, even under the highest 100-year flow conditions (flow scenario 3). Contraction scour at the bridge would not be expected since the overbanks through the bridge are slightly wider than the overbanks immediately upstream of the bridge. The bridge opening, therefore, does not represent a constriction to 100-year flows in the creek. Pier scour would not occur since no piers are being designed for the proposed bridge opening. Finally, abutment scour would be negligible since the abutments are located almost entirely outside of the 100-year floodplain. Under the most extreme 100-year flow conditions (flow scenario 3), flood levels would barely reach the vertical abutment and velocities would not be fast enough to cause any appreciable scouring conditions. No scour analysis of the next downstream bridge at SW 16th Street was conducted, so it was not determined whether the channel improvements would affect scour conditions at this bridge. Summary of Results The results of the HEC-RAS analysis indicate that the proposed bridge and channel improvements will reduce existing 100-year flood levels up to a maximum of 0.2 feet through this reach of Springbrook Creek. The walkway beneath the bridge would not be inundated by the 100-year flood, except by the highest 100-year flow scenario (scenario 3), in which case the walkway would be inundated up to 0.7 feet. Under these conditions, the 100-year flood elevation is well below the level required to satisfy the 2 foot bridge clearance criteria. Assuming the pumps at the BRPS are completely shut down, the 100-year flood levels are 5 increased, though the 2-foot bridge clearance criteria is still nearly met under these worst case conditions. Maximum overbank velocities beneath the proposed bridge will be higher under future 100-year flow conditions since overbank roughnesses beneath the bridge will be the same and since future 100-year flows will be higher. Peak velocities in the left and right overbanks at the bridge are predicted to be roughly 31/2 and 3 feet per second, respectively, under future flow conditions. Upstream and downstream of the bridge, peak overbank velocities were predicted to be higher immediately after construction than after the plants become well established under future flows. Peak overbank velocities ranged from roughly 2 to 41/2 feet per second immediately after construction. Peak velocities in the main channel are predicted to be slightly lower than current peak velocities as a result of the proposed channel improvements. Finally, the model predicted that the proposed bridge and channel alignment will not produce any appreciable scouring conditions. BANK PROTECTION Using the maximum overbank velocities predicted by the HEC-RAS model and the proposed bank slopes through the bridge, the required slope protection for each bank beneath the bridge was determined. The attached nomograph, provided in the 1990 King County Surface Water Design Manual for the design of riprap protection in open channels, was used to size the rock material for the bank protection beneath the bridge. Along the left bank (facing downstream), a peak velocity of 31/2 feet per second in combination with a 3:1 slope would require a graded rock material with a median diameter of at least 2 inches. For the right bank, a peak velocity of 3 feet per second along a 9:1 slope would require a graded material with a slightly smaller median diameter. While quarry spalls may work in this application, it is conservatively recommended that either light loose riprap or hand placed riprap be used to stabilize both banks beneath the bridge. Upstream and downstream of the bridge, all graded areas within the overbanks of the creek should be covered to help prevent erosion. An excelsior blanket or coir matting would be appropriate for this application until the plants in the overbanks become well established. However, the specific type and placement of fabric should be coordinated with the proposed landscaping plan for these areas. REFERENCES NHC, 1996. ESGRWP Hydrologic Analysis Final Report. March. King County, 1990. King County, Washington Surface Water Design Manual. King County Department of Public Works. January. Renton, 1997. ESGRWP Final Plan and EIS. September. RW Beck, 1996. ESGRWP Hydraulic Analysis Report, Existing Drainage System. March. 6 THE CITY OF RENTON DEPARTMENT OF PLANNING/BUILDING/PUBLIC WORKS FOURTH FLOOR 200 MILL AVENUE SOUTH RENTON, WASHINGTON 98055-2189 FAX: 235-2541 To: Gregg Farris Company: Phone: Fax: From: Scott Woodbury Phone: 425-277-5547 Fax: 425-235-2541 Date: 11/7/97 Pages incl this cover page: 5 Attached are my comments(hopefully final)to your 11/4 fax of the Oakesdale/Springbrook hydraulic analysis. In the model I changed the overbank location in all geometry scenarios at Sta 5930 to elevation 4 either side of the low flow channel. I also changed the n-value to 0.09 for the right bank of Sta 5930 between elevation 4 and 7 to be consistent with the rest of the sections. I ran the revised model and used the results to edit your memo. Finally,please call to discuss the velocities in the overbank. I will e-mail the revised model to you after we have discussed this fax. Thanks. 11/05/97 15:32 FAX ENTRANCO ENG. 10001/008 © E N T R A N C C ENGINEERS. ScIENTISTS, PLANNERS. SURVEYORS 10900 NE 8th Street,Suite 300 (206)454-5600 Bellevue,Washington 98004 Fax No.(425)454-0220 FACSIMILE TRANSMITTAL Date November 4, 1997 PLEASE DELIVER THE FOLLOWING PAGES IMMEDIATELY TO: Name Scott Woodburki Firm/Agency City of Renton City Renton Fax Number 235-2541 From Gregg Farris Project/Promo Name Oakesdale Bridge Project/Promo No. 97027-21 Remarks/Items Transmitted: Scott, Attached is the revised HEC-RAS technical memorandum for the Oakesdale Bridge project. The model was run again to correct the channel roughness error at station 5975 as you had noted. I also revised the peak velocities as noted in the technical memorandum. The peak velocities were determined from close examination of the cross section plots, so let me know if these still appear to you to be wrong. I also revised the bridge clearance section of the memorandum and made most of the other changes that you had suggested. If the technical memorandum looks fine, then I will mail an original copy. I will also e-mail the latest version of the HEC-RAS model to you again. If you have any questions, please feel free to call me. Thank you. Gregg Hard Copy E Will Will Not Be Sent No. of Pages (Including Transmittal Sheet) 7 If there are problems with transmission, call Gregg (425) 454-5600 The information in this fax is confidential and proprietary and is intended only for the individual or entity named on the cover sheet. If you are not the intended recipient, disclosure, copying, distribution or use of this information is prohibited. If you do not receive all of the pages or have received this fax in error, please notify us immediately at the above telephone number. S:\ENM3008-78\out—mail4WSDFWfxl.doc 11/05/97 15:32 FAX ENTRANCO ENG. 10002/008 MEMORANDUM Date: November 5, 1997 To: Scott Woodbury From: Gregg Farris cc: Bruce Jensen, Peter DeBoldt Subject: HEC-RAS Analysis of Springbrook Creek at Proposed Oakesdale Bridge A HEC-RAS analysis of Springbrook Creek was performed to determine the effects of the proposed Oakesdale Bridge and the associated channel improvements upon the creek. The analysis was also used to support the design of channel stabilization improvements along the banks of the creek. The proposed bridge is located roughly 300 feet upstream of the existing SW 16th Street Bridge within the City of Renton. Channel improvements are primarily located between the two bridges as well as immediately upstream of the proposed bridge. These improvements generally involve widening the overbank portions of the creek and avoid altering the low-flow channel within the creek. All elevations in this analysis are referenced to the NGVD 1929 vertical datum. HEC-RAS MODEL The HEC-RAS model of Springbrook Creek used for this analysis was supplied by Northwest Hydraulics Consultants, Inc. (NHC). The model was originally created as a HEC-2 model by NHC in conjunction with RW Beck (NHC, 1996) and was subsequently converted into a HEC- RAS model specifically for this analysis. While an FEQ model of the creek was also available, the HEC-RAS model was chosen for this analysis since it is better suited to analyzing a variety of alternative scenarios than the FEQ model. The model extends from the Black River Pump Station (BRPS), which discharges into the Black River, upstream to SW 43rd Street, which represents the border between Renton and Kent. Three flow scenarios were input into the model, all of which were based on the 100-year flood event under a variety of assumed conditions. Both existing and future land use conditions throughout the basin were considered as well as the construction of improvements along the creek upstream of Oakesdale Bridge. The impact of the upstream channel improvements, once constructed, would be to increase peak flow rates at Oakesdale Bridge. 1 11/05/97 15:33 FAX ENTRANCO_ENG. 4 003/008 The specific flow rates for each scenario are listed in Table 1. These flow rates were generated by a combination of hydrologic and hydraulic models of the creek developed by NHC and RW Beck. The first model was developed using HSPF to perform a hydrologic analysis of the basin and to develop inflow hydrographs at specific locations along the creek. The HEC-2 model previously described was originally created to develop specific input (F-table) data for the HSPF model. The inflow hydrographs generated by HSPF were then input into an FEQ model of the creek. After routing these hydrographs through the creek, the peak 100-year flow rates generated by the FEQ model were used as the input flows for the HEC-RAS model used in this analysis. In general, the HEC-RAS results compared reasonably well with the FEQ results at many locations throughout the creek, though a direct comparison at the proposed bridge location could not be made. Table 1 Flow Scenarios Used in HEC-RAS Analysis 100-yr Flow at Downstream Flow Upstream Channel Oakesdale Boundary Water Scenario Land Use Improvements Bridge (cfs) Elevation (ft) 1 Existing Prior to Upstream Alt 3 934 4.1 Improvement (per NHC 1996) 2 Future Prior to Upstream Alt 3 1,106 4.1 Improvement (per NHC 1996) 3 Future After Upstream Alt 3 1,383 4.35 Improvement (per Renton 1997) The water surface elevations at the downstream boundary (i.e. the BRPS) for each flow scenario are also listed in Table 1. These elevations were generated by the FEQ analysis (RW Beck 1996), which was based on the pump station operation procedures. Under current procedures, the first of the larger pumps are manually turned on when the water surface at the pump station exceeds an elevation of approximately 4 feet, while additional pumps are added at 0.5-foot increments (see RW Beck 1996). The elevations in Table 1 represent an interpolated average. King County has the authority to completely shut down the pump station during extreme flood conditions in the Green River, forcing water to be stored in the creek upstream of the pump station. This scenario is described in further detail in the following bridge clearance discussion. In addition to the above flow scenarios, three geometry scenarios were developed for the HEC- RAS analysis related to the proposed Oakesdale Bridge improvements. These scenarios are listed in Table 2. Near the Oakesdale Bridge, the existing channel geometry is based on recent survey measurements and a digital terrain model created for the bridge project. The future channel geometry is based on the proposed channel improvements currently being designed for the bridge project. 2 11/05/97 15:34 FAX ENTRANCO ENG. 10 004/008 Table 2 Geometry Scenarios for HEC-RAS Analysis Within Study Reach v Channel Roughness �i Geometry Channel Geometry Within Conditions Within Manning's n Manning's n in Scenario Study Reach Study Reach in channel overbanks Hv 1 Existing (before Existing Roughness 0.035 0 Oakesdale bridge/channel 0.05/.07 X �? improvements) 3 Z Future (after Oakesdale Before plants well 0.0403 0.0251 bridge/channel established S improvements) Future (after Oakesdale After plants well 0.0403 0.090/0,0751,2 bridge/channel established improvements) 1. The only exception is beneath the bridge,where a value of 0.035 was used to represent riprap on each overbank 2. As directed by Scott Woodbury of Renton,0.090 was applied from the top of the low-flow channel up to an elevation of 7.0 feet (approximate 2-yr elevation)while 0.075 was applied above elevation 7.0 feet 3. Assumes that woody debris will be added to channel as a requirement for obtaining an HPA permit Different channel roughnesses were also considered for each scenario. Existing channel roughness values within the study reach were estimated in the original setup of the model based on observation rather than on calibration of the model. The overbank roughness values for the study reach are higher than the values used for the existing upstream reaches. Channel roughnesses immediately after construction of the Oakesdale improvements are assumed to be lower since the plants on the graded banks will not be well established. Once the plants become well established, then the roughness values will increase, as indicated in Table 2. For this scenario, roughness values were assumed to be 0.090 from the top of the low-flaw channel up to an elevation of 7.0 feet, which is roughly equal to the 2-year water surface elevation. Above 7.0 feet, the roughness values were assumed to be 0.075. The difference in assumed roughness values above and below 7.0 feet reflects the difference in the type of vegetation proposed for the upper and lower regions of the channel banks. RESULTS OF HEC-RAS ANALYSIS The HEC-RAS model was used to analyze water surface elevations, velocities, and scour conditions that would result from the installation of the proposed Oakesdale Bridge and the associated channel improvements in Springbrook Creek. Water Surface Elevations Changes in the 100-year water surface elevations caused by the proposed bridge and channel improvements were estimated for both existing and future land use conditions (flow scenarios 1 and 2). In each case, widening of the overbank areas along Springbrook Creek near the proposed bridge resulted in a reduction of flood levels throughout this reach of the creek. Since flood levels are not increased at any location, this satisfies both local and federal floodplain management regulations. For existing land use conditions, the maximum reduction in 100-year 3 11/05/97 15:35 FAX ENTKANCO ENG. LIL005/008 flood levels near the bridge was predicted to be approximately 0.2 feet, while for future land use conditions, the maximum reduction was approximately P<`fe t. Tabl 3 summarizes the 100-year water surface elevations predicted by the l- C-RAS model at the upstream face of the proposed bridge I p p edge for all three flow scenarios. T+rese results-.-assunie t the--vegetation on each bank_has become- well- established (geometry._._.__ Table 3 Predicted 100-Year Flood Elevations -11,4 , tWProposed Oakesdale Bridge V e low y mid i. at FI 3 Scenario Upstream Face Dow akeam Face 1 g,sy g,34 *2 �.oy 2 0-7 S?, g 2- � 8. `19 3 91 — 1,68 .9 s ,�' 2- Under the highest flow conditions (flow scenario , the 100-year flood elevations vary between 9.6 to 9.7 feet through the bridge. This is slightly higher than the elevation of the proposed walkway beneath the bridge, which is currently designed at an elevation of 9.0 feet. During the most extreme 100-year flow conditions, therefore, the proposed walkway could be inundated with up to 0.7 feet of floodwater. Bridge Clearance One of the design requirements for the bridge structure was that the design clearance must be a minimum of 2 feet per City of Renton requirements. The design clearance is defined as the vertical distance between the design water surface and the bottom of any part of the bridge (i.e. the low chord). Since the lowest part of the proposed Oakesdale Bridge is currently designed at an elevation of 14.9 feet, the design water surface should be below 12.9 feet. As indicated in Table 3, the 100-year flood elevation at the bridge is well below elevation 12.9 feet for each of the 100-year flow scenarios. These scenarios assume that the BRPS will not be required to reduce pumping rates due to high flow conditions in the Green River. If the pump rates at the BRPS must be reduced or completely shut off in accordance with the Green River Interlocal Agreement, then higher flood levels will result as water is stored in the creek upstream of the pump station. The 100-year water surface elevation for this scenario was determined by the previous FEQ analysis to be 13.0 feet at the Oakesdale Bridge (RW Beck 1996), which resulted in a bridge clearance of 1.9 feet. As a result, the bridge nearly meets the required e�t clearance requirement even under this worst case!scenario. Maximum Velocities The maximum velocities along the overbanks of the creek channel were determined for the design of bank stabilization improvements beneath the proposed brides� Velocities were determined using the existing 100-year flow rate (flow scenario 1) in Zmbation ith channel 4 11/05/97 15:35 FAX ENTKANCO ENG. _ 1O006/008 conditions immediately after construction (geomet scenario ) as well as using future 100- year flow rates (flow scenario 3) in combination with hannel conditions after the overbank plants had become well established (geometry scenari 0). Because overbank roughnesses directly beneath the bridge will be the same immediately after construction as under future flow conditions, due to the proposed use of rock for slope protection under the bridge, the overbank velocities produced by the future flow conditions (flow scenario 3) will be higher. immediately after construction, the peak velocities beneath the bridge along the left and right overbanks are predicted to be roughly 3 and 2 feet per second, respectively. Future peak velocities in the left and right overbanks are predicted to be roughly 3'/2 and 3 feet per second, respectively. Upstream and downstream of the bridge, peak overbank velocities were predicted to be higher immediately after construction than after the plants become well established under future flows. Immediately after construction, when overbank roughnesses are lower, peak overbank velocities ranged from roughly 2 to 41/2 feet per second. Under future conditions, peak overbank velocities were reduced to between roughly 1 to 31/2 feet per second. Velocities in the main channel of the creek were generally reduced following the installation of the proposed bridge and channel improvements. Bridge Scour The HEC-RAS model was also used to predict bridge scour during the 100-year flood for the proposed channel. The model predicted that the proposed channel alignment through the bridge would not cause any appreciable scouring conditions, as expected, even under the highest 100-year flow conditions (flow scenario 3). Contraction scour at the bridge would not be expected since the overbanks through the bridge are slightly wider than the overbanks immediately upstream of the bridge. The bridge opening, therefore, does not represent a constriction to 100-year flows in the creek. Pier scour would not occur since no piers are being designed for the proposed bridge opening. Finally, abutment scour would be negligible since the abutments are located almost entirely outside of the 100-year floodplain. Under the most extreme 100-year flow conditions (flow scenario 3), flood levels would barely reach the vertical abutment and velocities would not be fast enough to cause any appreciable scouring conditions. No scour analysis of the next downstream bridge at SW 16th Street was conducted, so it was not determined whether the channel improvements would affect scour conditions at this bridge. Summary of Results The results of the HE 4AS analysis indicate that the proposed bridge and channel improvements will reduce 100-year flood levels up to a maximum of 0.2 le-Qd feet through this reach of Springbrook Creek. The walkway beneath the bridge would not be inundated by the 100-year flood, except by the highest 100-year flow scenario (scenario 3), in which case the walkway would be inundated up to 0.7 feet. Under these conditions, the 100-year flood elevation is well below the level required to satisfy the 2 foot bridge clearance criteria. Assuming the pumps at the BRPS are completely shut down, the 100-year flood levels are increased, though the 2-foot bridge clearance criteria is still nearly met under these worst case conditions. Maximum overbank velocities beneath the proposed bridge will be higher under future 100-year flow conditions since overbank roughnesses beneath the bridge will be the same and since 5 11/05/97 15:36 FAX ENTRANCO ENG. _ _ _ _ _ I0 007/008 future 100-year flows will be higher. Peak velocities in the left and right overbanks at the bridge are predicted to be roughly 3'/2 and 3 feet per second, respectively, under future flow conditions. Upstream and downstream of the bridge, peak overbank velocities were predicted to be higher immediately after construction than after the plants become well established under future flows. Peak overbank velocities ranged from roughly 2 to 4'/2 feet per second immediately after construction. Peak velocities in the main channel are predicted to be slightly lower than current peak velocities as a result of the proposed channel improvements. Finally, the model predicted that the proposed bridge and channel alignment will not produce any appreciable scouring conditions. BANK PROTECTION Using the maximum overbank velocities predicted by the HEC-RAS model and the proposed bank slopes through the bridge, the required slope protection for each bank beneath the bridge was determined. The attached nomograph, provided in the 1990 King County Surface Water Design Manual for the design of riprap protection in open channels, was used to size the rock material for the bank protection beneath the bridge. Along the left bank (facing downstream), a peak velocity of 3'/2 feet per second in combination with a 3:1 slope would require a graded rock material with a median diameter of at least 2 inches. For the right bank, a peak velocity of 3 feet per second along a 9:1 slope would require a graded material with a slightly smaller median diameter. While quarry spalls may work in this application, it is conservatively recommended that either light loose riprap or hand placed riprap be used to stabilize both banks beneath the bridge. ��,�G2 Upstream and downstream of the bridge, all g ed areas within the overbanks of the creek should be covered to help prevent erosion. A gem blanket or coir matting would be appropriate for this application until the plants in the overbanks become well established. However, the specific type and placement of fabric should be coordinated with the proposed landscaping plan for these areas. REFERENCES NHC, 1996. ESGRWP Hydrologic Analysis Final Report. March. 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