The Willow Creek Reclamation Committee has initiated several studies in the watershed to quantify flood levels and identify flood hazards. In 2002, Agro Engineering was contracted to conduct a flood control and stream stability study from the lower reaches of East and West Willow Creek, downstream to the entrance to the Creede Flume. (Read More Below)
Also in 2002, Steve Yochum, Hydrologist for the Natural Resources Conservation Service, conducted two studies on behalf of the WCRC. The first, entitled Flood-Frequency Analysis Report for Willow Creek, was a cooperative effort with the Colorado Water Conservation Board to conduct a discharge-frequency analysis for the Willow Creek watershed. The second, entitled Hydraulic Analysis Report, provided the results of a hydraulic analysis of the Creede Flume. This study determined the capacity of the flume, identified obstacles to flow in the flume, and pinpointed locations where high flows would first leave the flume. In 2003, Yochum continued his research on Willow Creek by conducting Regional Bankfull Characteristics for the Lower Willow Creek Stream Restoration. This report documents the development and application of regional bankfull curves for application by the NRCS and other partners as they design the restoration of Willow Creek below Creede.
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The Upper Willow Creek Watershed Flood Control and Stream Stability Study
The Upper Willow Creek Watershed Flood Control and Stream Stability Study was conducted by Agro Engineering, Inc. for the Willow Creek Reclamation Committee in Creede, Colorado. Funding was provided by the Colorado Water Conservation Board (CWCB) and the Federal Emergency Management Agency’s (FEMA’s) Project Impact.
The primary purpose of the study was to analyze Upper Willow Creek for flood control and debris/sediment problems, and develop a plan to address these problems. The study reach was limited to the portion of Upper Willow Creek and its associated watershed above the masonry flume in downtown Creede. The goals of the study were to:
1) Quantify the risk of flood damage from Upper Willow Creek
2) Examine problems related to debris and sediment transport in Upper Willow Creek
3) Develop strategies to reduce the risk of property damage and destabilization of potential pollution sources during flood events and improve the aesthetic qualities, habitat conditions, and physical functioning of Upper Willow Creek
A study report was presented to the Willow Creek Reclamation Committee.
Note: The entire report is quite large. Please contact the Willow Creek Reclamation Committee director for a CD or paper copy of the report.
55 stream cross-sections were surveyed in Upper Willow Creek. These cross-sections were used in the U.S. Army Corps of Engineers’ Hydraulic Engineering Center River Analysis System model (HEC-RAS) to model the channel hydraulics of Upper Willow Creek. Color aerial photos were taken of the floodplain and used with additional survey data to map high-resolution topography in the floodplain. Flood inundations at various flood return intervals were mapped in GIS using water surface elevations from the HEC-RAS model and the high-resolution topography. The GIS files for these flood plains can be download here. The floodplain analysis indicated several potential locations of flooding that are described in the project report. Potential flooding problems of major concern include:
A flume and metal pipe carry West Willow Creek over and through the large Commodore mine tailings pile. A 10-year flood will cause flooding of the depressed area at the pipe entrance. A 25-year flood will overtop the tailings pile, causing a high velocity flow down the very steep face of the pile. This event could potentially erode tons of mine tailings and mine debris into Willow Creek. Fine tailing sediments would probably be carried by the flood into the Rio Grande potentially causing a major fish kill.
Overtopping of Weir Above Mining Museum Area
The earthen and wood weir upstream of the mining museum area will be overtopped starting at the 25-year flood return interval. Flood flows will enter the depression west of the main channel and flow downstream into the parking area east of the mining museum. However, these flows should re-enter Willow Creek and be contained by the levees of the masonry flume.
Windy Gulch Culvert
The roadway below Windy Gulch (just below the mining museum) will be overtopped during flood events initiating at the 10-year level. A portion of the overtopping flow will flow down the road and potentially cause flooding in downtown Creede.
North Creede Culvert
The hydraulic analysis indicated that the culvert in North Creede will be overtopped in nearly all flood events. Personal accounts of flooding indicate that floods typically erode the roadway near the culvert. A large flood will probably damage surrounding structures.
Many areas of the Willow Creek channel were noted to have significant amounts of timber debris. This timber debris will be easily mobilized during small flood events and could easily plug culverts or other structures.
Watershed Sediment Sources
Specific sediment sources in the Willow Creek watershed that may be contributing sediments to the Willow Creek channel were identified using aerial photography and delineated in GIS. Mapped sediment sources included areas of mine tailings, mine related disturbance, mobile talus/scree, and roadways.
Alternate Mitigation Strategies
Mitigation strategies were developed to address problems that were identified. Preliminary designs and approximate cost estimates were developed for a number of projects. The following figure shows the location of potential projects. These projects are in detail in the Chapters 3 and 4 of the report.