Resolution_TO5_WSE - Laserfiche WebLink

Home Browse Search

Q 0, WATERSHED SCIENCE & ENGINEERING April 30, 2024 Assumptions: • City and County staff and the CPT will support the collection of data, photos, and accounts of flooding. • Except for GIS flood history data, no new data will be created in this task. • The climate change evaluation will be qualitative and descriptive and will not be modeled unless it is determined necessary and sufficient budget remains, as directed by the City's and County's project manager. Deliverables: • WSE contributions to the draft and final City Conditions Memo. Task 2.4. Stormwater Model WSE will not have any specific tasks related to the stormwater model Task 2.5. Update Hydraulic Model WSE will update and refine the existing HEC-RAS 2D hydraulic model of Whiskey and Mercer Creek within the City of Ellensburg using data gathered in Tasks 2.2 and 2.3. The model will comply with the FEMA guidelines and standards for flood risk analysis and mapping. WSE will update the model to: • Incorporate new topographic data and survey identified or collected In Task 2.2 • Refine model mesh to improve model resolution based on flood mapping analysis completed in Task 2.3 • Incorporate significant stormwater inflow and/or outflow locations modeled in Task 2.4 WSE will then run the model for the 100-year flood event and one other flood event determined through coordination with the Tech Team. Model results will be presented to the Tech Team in Task 2.1 to assess the level of accuracy, identify primary flow paths, and compare to the results of stormwater modeling completed in Task 2.4. WSE will complete additional model refinements, if necessary, based on stakeholder input. WSE will create a topographic workmap of the resulting 100-year inundation mapping and develop a brief technical memo to document the model updates. Assumptions: • Modeling will be completed by updating Whiskey -Mercer HEC-RAS 21) model that was most recently updated in 2023. Deliverables: • Updated HEC-RAS model that complies with FEMA guidelines and specifications for flood risk assessment and mapping. • A topographic workmap showing draft 100-year inundation extents based on most current FEMA methods as determined in Task 2.3. 0 Brief technical memo documenting model updates