FLOODC00261 - Laserfiche WebLink

Home Browse Search

HEC models and aerial mapping north of the Adams/Weld County Line was done by the CWCB and cross sections and data is new and is done in HEC-RAS format. The areas south ofthe Adams/Weld County line through Denver are much more convoluted and spotty due to site specific studies driven by development done by UDFCD. The key issue here is that the UDFCD is not using the standards ofNGVD 1929 vertical datum or the NA VD 1988 vertical datum. There are roughly 50 bridges that made modeling tougher for George Cotton and he had to fuss with them individually to get the model to work properly. Most agreed that increased flow and flooding potential would have a minimal chance of leaving the channel through the Denver reach but the problems would arise from Henderson gage on downstream. Inflows from Clear Creek and Sand Creek had less effect and impact than George Cotton had initially thought they would and we surmised that inflows were relatively stable from these two tributaries. Additional Study Investil!ations . Storal!e Use Patterns Investil!ation The project sponsor, Colorado Water Conservation Board (Board), has a responsibility to perform a storage use pattem study for the project. The fl11dings and recommendations of the study will be the design criteria for the space allocation determinations. The Board will be contracting the services of a consultant for $25,000 for the performance of the certain tasks. The study will evaluate the following assumptions: 1. Assume that a maximum of 20,000 acre-feet of water supply will be used; 2. Review the Denver Water Board's (DWB) current operations of the 10,000 ac-ft water supply pool; 3. Review the annual operations for the 27,000 ac-ft@ 5432 normal pool and 17,000 ac-ft permanent pool; 4. Develop new demand curves for wet and dry year conditions; 5. Evaluate storage pattem opportunities based on environmental demands and controls "The mouse"; 6. Consider that reservoir recreational features are not an operational variable; and 7. Compile and evaluate the conditional storage rights and any storage opportunities that may exist in the water community. . Mappinl! and Floodplain Study An opportunity exists to update and prepare new 100- year floodplain information report for the South Platte River. This study has or will develop new surveys and mapping for the South Platte River Floodplain areas. New software/programs exist now that can cheaply replace the Board's 1970s designation, delineation and reports. George and Larry met to discuss these additional study tasks and have determined that they can be accomplished within existing funding. The consultant will help us get a better picture ofthe water rights situation on Chatfield and the South Platte. George will subcontract with another consultant to fill in data gaps found between gages along the South Platte River. George told us about additional aerial mapping that UDFCD is doing in Denver for one of their projects. Fundinl! issues Rick Miner and Larry will work together to come up with a budget picture and project schedule. There are a number of additional study tasks which were identified by the Corps. Additional funds will be requested next fiscal year. We discussed the transition of study fl11dings to the Environmental Impact Statement. We will need to get State Parks involved at the July meeting to get and idea ofa cost/benefit analysis for each level of pool increase regarding recreation. We don't have specific dollar values for the levels of inundation and relocation of State Parks Flood Protection. Water Project Planning and Financing. Stream and Lake Protection Water Supply Protection. Conservation Planning