Use the tabs below to explore key takeaways from the Phase I existing conditions analysis, including what data was reviewed, how the watershed was modeled, what the results showed, and how these findings inform the path forward.

The project team collected and reviewed digital mapping data (GIS data) showing storm pipes, inlets, manholes, open channels, and detention basins across the watershed. They checked this information for missing or incomplete pieces that could affect how accurately flooding is modeled. They also used terrain data, land‑use information, soil types, and rainfall data from NOAA to understand how stormwater moves across the landscape.

Two types of stormwater modeling approaches were compared to understand how water flows during storms:

• CUHP (1D rainfall‑runoff modeling) – estimates how much runoff is created in each small drainage area.
• Rain‑on‑Mesh (2D modeling) – simulates how water spreads and flows across the ground surface.

After comparing these methods, the team built a full hydrology and hydraulics model of the entire watershed. This combined:

• Rainfall patterns
• How water runs off different land surfaces
• How stormwater interacts with pipes, inlets, channels, and detention basins
• Flooding behavior during storms ranging from 2‑year to 500‑year events

The model produced maps showing water depth, flow velocity, and flood hazard levels.

The 100‑year storm results revealed several areas where flooding poses risks to homes, businesses, roads, parks, and trails. In some locations, stormwater inlets and manholes were shown to overflow or become pressurized during large storms. Some areas reached the highest hazard category, meaning floodwaters could be dangerous for both people and vehicles.

To improve accuracy, additional small storm pipes and inlets were added to the model where needed. All final results were delivered in digital map formats for use by the City and County of Denver and Mile High Flood District.

The team used these findings to shape the flood‑risk reduction improvements now being advanced in Phase II. To learn more about those improvements, please visit the Phase II Proposed Improvements page.