FLOOD10377 ‎(3)‎

• County: Weld
• Community: Fort Collins
• Stream Name: Cache La Poudre River
• Title: Volume II - Hydraulic Analysis for the Cache La Poudre River between Timnath Diversion Dam and College Ave. - Appendix G.5
• Date: 4/11/2006
• Prepared For: Fort Collins
• Prepared By: Anderson Consulting Engineers, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

RCIOOQ06.0H2

MODEL WAS NOT UPDATED IN EITHER THE 2001 POWER PLANT DROP
STRUCTURE/BOAT CHUTE LOMR OR THE 2005 (REVISED JANUARY 2006)
CACHE LA POUDRE REMOVAL ACTION LOMR BECAUSE THE CHANGES ASSOCIATED
WITH THESE LOMR' S DID NOT AFFECT THE 100-YEAR FLOW SPLITS.
2. INCORPORATES THE CHANGES ASSOCIATED WITH THE 2001 POWER PLANT
DROP STRUCTURE/BOAT CHUTE LOMR AND THE 2005 (REVISED JANUARY
2006) REMOVAL ACTION LOMR.
3. COMPUTES DISCHARGES FOR THE 100-, 50-, AND 10-YEAR SPLIT FLOW PATHS
DEFINED BY THE SPLIT FLOW CARDS AND COMPUTES THE 100-, 50-, AND
10-YEAR WATER SURFACE ELEVATIONS FOR THE MAIN CHANNEL.
4. CHANGED THE 87 IN FIELD 5 OF THE JP CARD FOR THE LINCOLN SPLIT FLOW
CARDS TO 100. THIS MODELING CHANGE WAS MADE DUE TO THE FACT THAT
THE "HARD WIRING" OF DISCHARGES WAS NECESSARY TO ACCOUNT FOR FLOW
IN THE MAIN CHANNEL AND THE LINCOLN DIVIDED FLOW PATH WHEN THE UPPER
AND LOWER REACHES WERE SEPARATE MODELS. NOW THAT THE MODELS HAVE BEEN
COMBINED AND THE FACT ONLY A SMALL PORTION OF FLOW (APPROXIMATELY 4
CFS IN THE 100-YEAR PROFILE) DID NOT RETURN TO THE MAIN CHANNEL OVER
LINCOLN AVENUE, IT IS ASSUMED THAT ALL FLOW SPILLED INTO THE LINCOLN
DIVIDED FLOW PATH WILL RETURN TO THE MAIN CHANNEL UPSTREAM .oF THE
MULBERRY BRIDGE, THIS PROVIDES A MORE AUTOMATED AND CONSERVATIVE
MODEL,
5. DELETED ALL OF THE 500-YEAR DISCHARGE INPUT FROM ALL QT CARDS FROM THE
EFFECTIVE LOWER Q 100-, 50-, AND 10-YEAR FLOODPLAIN MODEL (LOWQ99.DAT)
SINCE 500-YEAR WATER. SURFACE ELEVATIONS WERE NOT COMPUTED UTILIZING
THIS CORRECTED EFFECTIVE MODEL.
6, TRUNCATED THE LEFT OVERBANK GEOMETRY FROM THE GEOMETRY DATA OF
CROSS SECTIONS 228117, 229322, AND 229477 DUE TO THESE AREAS
NOT BEING HYDRAULICALLY CONNECTED TO THE MAIN CHANNEL.
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THE FOLLOWING CHANGES WERE MADE DURING THE 2005 REMOVAL ACTION
LOMR.

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FILE: RCUPR05. DAT
THIS 2005 REMOVAL ACTI.oN LOMR REVISED CONDITION MODEL:
9. INCORPORATES AS-BUILT TOP.oGRAPHY FOR THE REMOVAL ACTION
SITE THE 1-FT AS-BUILT TOPOGRAPHY FOR THE REMOVAL ACTION
SITE WAS DEVELOPED FROM POST-PROJECT LAND SURVEYS CONDUCTED BY
BY NORTHERN ENGINEERING IN JUNE 2005, GEOMETRY FOR THE

o 9MARO 6

16:05:36

FOLLOWING CROSS SECTIONS WERE UPDATED UTILIZING THE AS-
:~L~i~~~~Y TOPOGRAPHY WERE APPRO~RIATEj 229:321., 229477,

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FILE: CEUPR05.DAT
THIS 2005 REMOVAL ACTION L.oMR CORRECTED EFFECTIVE MODEL:
1. IS BASED ON THE REVISED CONDITION MODEL UPPER-RC. DAT
FROM THE POWER PLANT DROP STRUCTURE/BOAT CHUTE LOMR
CONDUCTED IN 2001. THE 2001 POWER PLANT DROP STRUCTURE/BOAT CHUTE
LOMR REVISED THE 1994 UPPER.DAT FEMA MODEL BY ADDING TWO CROSS
SECTIONS (230193 AND 230355) TO REFLECT THE NEW GRADING ASSOCIATED
WITH THE DROP STRUCTURE.
2. COMPUTES 100-, 50-, AND 10-YEAR WATER SURFACE PROFILES FOR THE
MAIN CHANNEL. DISCHARGES UTILIZED TO COMPUTE THE WATER SURFACE
PROFILES ARE BASED ON THE SPLIT FLOW DISCHARGES DETERMINED FROM
THE 1994 UPPERQ.DAT MODEL.
.3...CHANGED .THE..STARTING WATER .sURFACE. ELEVATIONS FOR ALL PROFILES
TO MATCH THE OUTPUT OF THE EFFECTIVE LOWER 100-, 50-, AND 10-YEAR
FLOODPLAIN M.oDEL FROM THE 1999 TIMBERLINE ROAD LOMR LOMR (LOWQ99,DAT)
4. INCORPORATES UPDATED PRE-PROJECT TOPOGRAPHY BETWEEN THE
DOWNSTREAM SIDE OF LINDEN STREET, CROSS SECTION 228637, AND JUST
DOWNSTREAM OF THE B.N.R,R., CROSS SECTION 229997. TWO SETS OF
TOPOGRAPHY WERE UTILIZED TO UPDATE THE HYDRAULIC MODEL. 1-FT PRE-
PROJECT TOPOGRAPHY FOR THE REMOVAL ACTION SITE WAS DEVELOPED FROM
LAND SURVEYS CONDUCTED BY NORTHERN ENGINEERING IN 2004. PRE-PROJECT
TOPOGRAPHY FOR PORTI.oNS .oF THE LEFT OVERBANK THAT WERE NOT
INCLUDED IN THE TOPOGRAPHY DEVELOPED FOR THE REMOVAL ACTION SITE
WERE .oBTAINED FROM THE COFC. THE C.oFC 2-FT TOPOGRAPHY WAS DEVELOPED
FR.oM AERIAL PHOTOS TAKEN IN 1999. GEOMETRY FOR THE FOLLOWING
EFFECTIVE CROSS SECTIONS WERE UPDATED UTILIZING THE PRE-PROJECT
TOPOGRAPHY; 228637, 228687, AND 229477. WHILE UPDATING THE
GEOMETRY FOR CR.oSS SECTION 229477 IT WAS DECIDED TO SHORTEN THE
GR DATA FOR THE RIGHT OVERBANK. THUS, CROSS SECTI.oN 229477
WAS SHORTENED BY APPR.oXIMATELY 800 FEET.
5, INCLUDES THE ADDITION OF TWO CROSS SECTIONS AT THE DOWNSTREAM
(229322) AND THE UPSTREAM (229757) ENDS OF THE REMOVAL ACTION
PROJECT SITE. PRE-PROJECT TOPOGRAPHY WAS UTILIZED TO DEVELOP THE
GEOMETRY FOR CROSS SECTI.oNS 229322 AND 229757,
6, CHANGED THE X3 CARD FOR CROSS SECTION 229477 INTO AN ET CARD AND
ADJUSTED THE LEFT ENCROACHMENT STATION OF 6770 .oN THE X3 CARD TO
STATION 7165 ON THE ET CARD TO REPRESENT THE INEFFECTIVE FLOW IN
THE LEFT OVERBANK CAUSED BY BUILDINGS UNDER CONSTRUCTI.oN IN THE
EFFECTIVE CONDITION PHOTO (IMPACTS 500-YEAR FLOWS ONLY) .
7. CHANGED THE LEFT ENCROACHMENT STATION OF THE X3 CARD FOR CR.oSS
SECTION 229997 FROM STATI.oN 8170 TO STATION 8170.1 SO THAT
THE ENCROACHMENT STATION WOULD LIE WITHIN THE GEOMETRY DATA, I
8. HAS A -1 INSERTED INTO FIELD 7 OF THE J2 CARD TO COMPUTE
CRITICAL DEPTH AT ALL CROSS SECTI.oNS. I
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Created .on 3/9/2006 4:06 PM