FLOOD10516 (2) - Laserfiche WebLink

Home Browse Search

Table 3.3 Summary of Effective COFC Models for Current Study. Effective Model Reach Limitsl Events Model Modeled Flow Splits Description/Purpose Name Downstream Upstream (return period) THFTFW A Y Horsetooth Taft Hill 100, Floodway Original 2000 tenth-foot rise floodway for main channel. Road Road --- Original 2000 water surface profiles and cross sectional 500DIST Horsetooth Taft Hill 500 flow distribution for main channel with split and diverted Road Road --- discharges removed. Cross-sectional flow distribution used to defme product 6 corridor. RCUPTF05 Horsetooth Taft Hill 100, Floodway 2005 Removal Action LOMR model c:omputing tenth-foot Road Road --- rise floodway for main channel. 2005 Removal Action LOMR model computing water Horsetooth Taft Hill surface profiles and cross sectional flow distribution for RCUP5D05 Road Road 500 --.., main channel with split and diverted discharges removed. Cross-sectional flow distribution used to define product 6 corridor, . . Model Reach LImIts: stream reach covered by the effectIve hydrauhc model. 3.2.2 Starting Water Surface Elevations and Roughness Coefficients Starting water surface elevations for the tenth-foot rise floodway model (RCUPTF05), and the 500-year cross sectional flow distribution model (RCUP5D05) were obtained from the Larimer County FIS restudy (November 17, 1993). The roughness coefficients utilized in the effective models were determined from the model input and were consistent throughout all of the models. In the current study reach, the Mmming's n value for the chmmel was 0.035 and the Mmming's n values for the overbank areas ranged between 0.040 and 0.104. 3.2.3 Tenth-Foot Floodway and Product 6 Corridor Results The original 2000 effective tenth-foot rise floodway and product 6 corridor ddineations from the Ayres, Inc. study were plotted on copies of the original FEMA workmaps and submitted in hardcopy to the COFC. Ayres also digitized these delineations into a GIS compatible format for inclusion in the City of Fort Collins' GIS database. The Ayres GIS work produc~ts are shown as the COFC effective workmaps on Sheet 1.1A. The linework obtained from the City of Fort Collins' GIS is considered to be the effective tenth-foot floodway and 500- year product 6 corridor delineations for the current study reach between Linden Street and Timnath Diversion Dam. For the current study between Linden Street and Cross Section AX:230912 the 2005 Removal Action LOMR revised condition mapping is considered to be the COFC2003-10 Oxbow FINAL LOMR,doc 3.8 ANdERSON CONsulTiNG ENqiNEERS, INC.