Colin Butler, Watershed Science & Engineering, Staff Hydraulic EngineerThese 100-year floodplain boundaries are intended to provide information about future inundation extents throughout the Chehalis River basin based on mid-range climate change projections. These data are not officially endorsed by Federal or Washington State agencies, and are intended for planning use only. This shapefile contains 100-year floodplain boundaries generated from a combination of hydraulic model results and topographic data geoprocessing. The boundaries were derived using the University of Washington Climate Impact Group's estimate of the moderate range of anticipated change to rainfall in 2080 - a 26% increase in precipitation - using down-scaled climate model data for the Chehalis Basin region. Details of the methods used to derive these floodplain extents are documented in a technical memorandum available from Watershed Science and Engineering (2021).ArcGIS FeatureLayerhttps://hub.arcgis.com/datasets/acf9323553b0423a8c53f39c35f9fcfe_1engState of Washington Geospatial Open Data PortalPublicChehalis Basin 100-year Floodplain - Mid-range Climate Change Projection [Washington (State)]Web servicesWashington (State)Last Modified: 2023-03-22