Desert Lakes Alluvial Fan Hydraulics Analysis

Riverside County, CA

PACE provided the baseline hydrologic analysis for a comprehensive and technically based design to provide the necessary flood protection and channel stabilization for the Desert Lakes project.  PACE provided a detailed technical analysis of (1) hydrology, (2) sediment yield/ sediment transport, (3) hydraulics, (4) two-dimensional alluvial fan hydraulics and (5) existing culvert hydraulics.

Desert Lakes is a 6400-acre proposed land development project in Riverside County located on several coalescing active alluvial fans.  At final build out, the project will include residential areas, a commercial town center, an 18-hole championship golf course, large restored park areas, and various restored alluvial channels.  The development is located in a desert alluvial fan area draining from the Little San Bernardino Mountains to the northeast.  The complete Desert Lakes project area is approximately 2,400 acres, while the upstream tributary area including the project area is approximately 16 square miles.

The proposed flood control improvements identified and evaluated in the technical investigation will assist in the long-term stabilization for this portion of the alluvial fan to allow development to occur with adequate levels of flood protection.  This project utilizes structural control measures and channelization to achieve the desired objectives, integrated with the regional flood control features of the watershed, which consist of the following:

  • Debris trapping channels on the upstream side of the project site to intercept sediment;
  • Training levees on the northern boundary of the project site to direct the flow into major storm water channels;
  • An incised trapezoidal channel with concrete slope revetment for the major stream courses;
  • Grade control structures within each of the channels to ensure the long-term streambed location; and
  • Dispersion channels on the eastern boundary of the project to return the runoff from a channelized form to a more natural sheet flow along the alluvial plain.