Arapahoe County, CO Environmental Rules: Coastal Development (2026)

Colorado is a landlocked state with no coastal development regulations, but Arapahoe County applies riparian and waterway protections analogous to coastal rules. Significant water features include Cherry Creek Reservoir (4-square-mile reservoir and state park), Cherry Creek itself (running north-south through the county to the South Platte), Plum Creek, Sand Creek, Toll Gate Creek, and the historic Highline Canal (71-mile agricultural canal now used recreationally). Arapahoe County Land Development Code §4-5 and city zoning codes typically require 50-100 foot riparian buffer setbacks from designated waterways measured from the ordinary high water mark. Wetland fill or alteration requires a Section 404 permit from the U.S. Army Corps of Engineers under the Clean Water Act. Floodplain development within FEMA-designated Special Flood Hazard Areas (100-year floodplain, Zone A/AE) requires elevation certificates and compliance with the community's floodplain ordinance—Arapahoe County participates in NFIP. The Cherry Creek Reservoir Watershed Protection Zone (5 CCR 1002-72) imposes strict phosphorus controls on development throughout the 225-square-mile watershed. Streambank stabilization requires permits. Aurora Reservoir and Quincy Reservoir have additional city-specific protections.