C-01 (Onion Creek Briefing).pdf — original pdf

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Onion Creek Questions Zoning and Platting Commission Watershed Protection Department October 2020 How is WPD overseeing the impact of the development along Onion Creek? • The Land Development Code and associated regulations are the overseeing guide to ensure that development does not cause adverse flooding impacts • Staff from the Development Services Department review development applications for compliance with regulations, including drainage, environmental, and water quality • Watershed Protection staff get involved if: o The development is in the floodplain (and some environmental review) o The applicant requests participation in the Regional Stormwater Management Program o If DSD staff requests assistance (ex. complex engineering modelling) • WPD staff interact with DSD staff through periodic training and providing resources/information to facilitate their review What overall impact will development have for residents, business and the current infrastructure along the OC floodplain? • A development application must prove that there will not be an adverse flooding impact on other properties o Flood levels in creeks o Performance of storm drain systems • The RSMP program provides a review of development impacts on a watershed scale What risk of new elevated floodplains are being presented? • There are no flood level increases expected along Onion Creek, or any creek, due to development in Austin based on the requirements in the Land Development Code (No adverse impact) • However, perceived flood risk along all creeks in Austin recently increased due to a better understanding of the risk based on the Atlas 14 rainfall study o WPD has initiated updates to floodplain studies to identify flood risk What will be the anticipated costs for additional buy outs that are not currently planned for? What is the status of pending buyouts and costs? • The selection of a buyout alternative is determined through evaluation of viable alternatives from extensive engineering studies • Buyouts are one alternative to achieve flood risk reduction for WPD projects • Active buyout project status: Project area # of homes in project # currently owned by City Lower Onion Upper Onion Middle Williamson 823 146 66 814 (99%) 118 (81%) 51 (77%) What flood analysis has been done on the OC watershed and what areas have you focused on. When was/were the analysis(s) done and what were the results? What is the estimated costs of analysis not yet completed and what is the timeline of those analysis? Floodplain Study Completion Date Result Approximate Cost 1997 2006 2013 COA OC Flood Control Study USACE OC Interim Feasibility Study USACE Hays Co. Interim Feasibility Study tributaries (current effective) N/A N/A N/A Feasibility analysis of mitigation options Updated FEMA maps; Feasibility analysis of mitigation options New FEMA maps (still preliminary); Feasibility analysis of mitigation options of mitigation options All of OC in COA and COA effective date: 3/2017 New COA and FEMA $1.1 M TC and several FEMA effective date: 1/22/2020 maps; Feasibility analysis All of OC and all tribs in COA and TC Possible COA effective date: 2022 Possible FEMA effective date: 2024 maps New COA and FEMA $3 M How is WPD informed of the proposed individual development projects that will impact the OC Watershed? • The Land Development Code requires that development does not cause adverse flooding to other properties • DSD reviews development applications for compliance with the Land Development Code • WPD gets involved with development applications through floodplain review, Regional Stormwater Management Program, and some environmental review How do the following entities coordinate with WPD in any efforts to prevent any additional loss of life or property downstream, including the SE Austin and Del Valle communities; A. Planning and Zoning; B. Environmental; C. Travis County; D. Transportation; E. Public Works • City departments coordinate activities through the LDC and normal operations to ensure that no adverse flooding impact regulations are followed • Austin coordinates development in our ETJ with the Single Office agreement with Travis County others • WPD is coordinating floodplain studies with Travis and Hays Counties, and • City of Austin, Travis and Hays Counties, and others have quarterly meetings with State Representative Goodwin and Council Member Kitchen to discuss ongoing flood risk reduction activities What flood mitigation efforts are being planned in collaboration with the City and County staff and current residents, businesses, and property owners for the Districts most impacted in this area of Onion Creek? Small Area Planning? • We are collaborating with Travis and Hays Counties on floodplain studies for Onion Creek being completed by Hays County and the City of Austin • WPD is currently implementing a buyout project in the Onion Creek Subdivision (Upper Onion Creek)