What is different downtown
- Creek proximity
- East Plum Creek runs along the west side of downtown. Parts of the corridor are mapped floodplain; check the current FEMA flood map and Town floodplain information for any specific property.
- Building age
- Downtown includes some of the oldest buildings in town, including commercial buildings, some built with locally quarried stone, alongside much newer infill.
- Building types
- Ground-floor retail and restaurants with offices or apartments above, plus older single-family homes on nearby residential streets.
- Jurisdiction
- Inside the Town of Castle Rock. Building permits, floodplain questions and storm drainage go to the Town.
How flooding tends to show up here
Downtown's flood exposure comes from two directions. East Plum Creek can rise during prolonged or very heavy rain upstream, and the low ground near the creek is where that risk concentrates. More often, though, the issue is street runoff: water from higher ground east of downtown flows down streets toward the creek, and short, heavy storms can overwhelm storm inlets. Ground-floor businesses with doors at sidewalk level and floor drains in back rooms are the usual entry points.
Older buildings add complications. Some have basements or partial cellars that were never designed to stay dry, stone or brick foundations with mortar joints that let water through, and decades of renovations layered on top of each other. When water gets in, cleanup can uncover older materials like plaster, old flooring and pipe insulation. Before demolition in an older building, ask whether materials should be tested for asbestos; Colorado requires certified professionals for regulated asbestos work, and CDPHE has guidance.
Mixed-use buildings also involve more people. A flood in a ground-floor shop may affect a tenant, a building owner, and residents upstairs who lose power or access. Clear communication and separate documentation for each party keeps insurance claims from colliding.
Common downtown flood situations
- Situation
- Street runoff during a cloudburst
- Likely entry point
- Front door threshold at sidewalk level
- First consideration
- Sandbags or door barriers before storms if the building has a history
- Situation
- Floor drain backup in a back room
- Likely entry point
- Rear storeroom or restroom drain
- First consideration
- Ask the building owner about a backwater valve
- Situation
- Water in an older cellar
- Likely entry point
- Foundation joints and old openings
- First consideration
- Check for older materials before demolition
- Situation
- High water on East Plum Creek
- Likely entry point
- Low-lying lots near the creek
- First consideration
- Follow Town alerts and evacuation guidance
- Situation
- Upstairs tenant affected by power loss
- Likely entry point
- Shared electrical service
- First consideration
- Coordinate with the building owner and utility
Questions for downtown owners and tenants
- Is my building in or near the mapped floodplain, and does my lender or insurer know it?
- Does the building have a backwater valve on its sewer line?
- If the building is historically significant, does exterior repair after a flood need any special Town review?
- Does my lease specify who handles flood cleanup for the structure versus fixtures and inventory?
- How does the Town notify downtown businesses about creek flooding?
General information for Castle Rock, not a quote or professional advice. In an emergency, call 911.