Location

Colorado Springs, CO

Client

Sterling Ranch Metro District

Services

Stream Restoration · Hydrologic Modeling · Hydraulic Modeling · Floodplain Analysis · Environmental Permitting

Sand Creek downstream of Arroyo Lane to upstream of Mustang Place is a hydraulically steep stream channel with headcutting and limited riparian vegetation, aside from sporadic willows and upland shrubs. The stream is expected to react with increased headcutting and degradation to additional development in the Sand Creek watershed. To mitigate the adverse effects of the proposed development, Sterling Ranch was required to design and construct channel improvements to stabilize this roughly 9,750-foot reach of Sand Creek.

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Naturalized Channel & Stream Restoration

JR Engineering understood that a standard channel with drop structures would not achieve the U.S. Army Corps of Engineers’ project requirements to obtain a 404 Permit, so JR contracted with a geomorphologist to assess the potential for a multi-stage naturalized channel design which would meet the emerging criteria for high-functioning, low-maintenance stream design.  The Sand Creek restoration featured a reduced number of boulder drop structures by widening the floodplain and carefully selecting wetland and riparian vegetation to provide hydraulic roughness and ecological uplift. The U.S. Army Corps of Engineers was receptive to the design, which minimizes impacts on existing wetlands, improves the health and diversity of the watershed ecology, and provides a wetland mitigation ratio far above the minimum requirement.

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Hydrologic & Hydraulic Modeling

JR Engineering was required to reassess the watershed hydrology with an updated Master Development Drainage Plan (MDDP) for Sterling Ranch.  This report utilized updated routed hydrologic modeling (CUHP and EPA SWMM) and detailed offline detention pond design information to define the creek’s peak flows used in channel design and the storage volumes for the in-line ponds.

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JR Engineering assessed the Sand Creek hydraulics with the proposed stream restoration design.  JR Engineering prepared a steady-state HEC-RAS hydraulic model to investigate shear stresses, velocities, and water surface elevations for the range of MDDP design storm peak flows.  Iterative revisions were made to the channel design to address areas of concern and ensure a stable stream corridor.

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Floodplain Analysis & CLOMR

Additionally, JR Engineering prepared a CLOMR using FEMA Flood Insurance Study (FIS) hydrology to propose map revisions to the Sand Creek floodplain resulting from the project.  The FIS flow rates exceeded the MDDP peak flows, and the design of the channel, ponds, structures, and culverts needed to safely pass the FIS flows while meeting NFIP floodplain regulations. The CLOMR required remapping of nearly 2 miles of stream and tying in to the effective floodplain and floodway on both ends of the project where other work had already been completed by others. The CLOMR became effective as of May 2025.