The purpose of the study is to analyze the existing and future drainage conditions with the Fourmile Canyon Creek and Wonderland Creeks floodplains, develop alternate drainageway planning concepts to mitigate existing flood damages, and prepare a preliminary design of facilities based on a master plan.

This project is unique in that during storm events greater than the 10-year frequency, flood waters spill out of Fourmile Canyon Creek and flow into the Wonderland Creek floodplain thus inundating the lands between the two creeks.

The study area includes approximately four miles of the Fourmile Canyon Creek and also many miles of Wonderland Creek located in the northern portions of the City of Boulder. The study is divided into two phases. The first phase covers the hydrologic, hydraulic, and alternate evaluation aspects of the project. The second phase covers the preliminary design of the selected alternate.

A hydrologic model was created using the latest versions of the CUHP hydrologic catchment modeling and the UDSWM hydrologic routing models, for the 2-, 5-, 10-, 50-, and 100-year storm events.

Hydraulic analysis was completed for the 10-, 50-, 100– and 500-year floodplains using the HEC-RAS water surface profile computer model.

A damage analysis of all property, structures and infrastructure within the 500-year floodplain was also developed.