Murrieta Creek Flood Control
Environmental Restoration and Recreation Project

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THE RESTORATION PLAN
Murrieta Creek has been altered since the late 1800's, and has been channelized for flood control since the 1930's. Restoration along the creek banks within the channel invert and in and around its tributaries and floodplain would not only bring back historic habitat functions, including surface and sub-surface hydrology, but also invite a large array of desired wildlife and plant species, including sensitive species, while potentially reducing the extent of undesirable exotic species. The ecological resources of Murrieta Creek and its associated hinterlands have been identified as a resource of extremely high concern. Several resource agencies, including the 11.5. Fish and Wildlife Service and U.S. Environmental Protection Agency, have indicated that Murrieta Creek is one of the last high quality minimally disturbed riverine environments in southern California. These same agencies have indicated that, prior to the destructive floods of 1993, there was a much higher quality environment associated wit the creek in many areas, particularly downstream of Warm Springs Creek. Much of the degradation has been caused by flood destruction of valuable riparian habitat. There is a significant opportunity to restore degraded habitat along Murrieta Creek in concert with flood damage reduction measures. Image 1
The Restoration Plan would create a natural riverine system within the detention basin site bounded by Santa Gertrudis Creek to the south and Warm Springs Creek to the north. Flows from Murrieta and Warm Springs would both flow through the excavated riverine zone, which would be excavated down approximately 10 feet to the elevation of the existing channel invert. Approximately 9120,000 cubic yards of material would be excavated; all of which would be disposed of offsite. The invert of the excavated area would be graded to a slope of 1000:1.5, with a higher grade at Warm Springs, and a lower one at the outlet into Murrieta Creek downstream. The site would be sloped both to drain the area, particularly that of the area farther from the channel centerline at a rate slower than that of the existing invert, and with the surficial contouring, would provide areas of slow-moving water and ponding.
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The on-line nature of this feature would receive channel inflow at all times that this would be available from both Warm Springs and Murrieta Creek. This will significantly increase infiltration compared to the existing condition. Initial contouring would create two low-flow channels, one on Murrieta Creek and one on Warm Springs Creek. Average width of the channels would range between 10 and 15 feet, with an average depth of 3 feet. Flows above those contained within the low-flow channels would have the opportunity to flood back channels and ponded areas.
Nine acres of freshwater ponds would be created which would receive flows at more frequent intervals and also by groundwater infiltration. Water stored in these ponds would exfiltrate, draining through the surrounding soils during drier periods (periods of lower groundwater elevation). The two ponds would average 4.8 and 4.4 acres, with a maximum depth of 6 and 8 feet respectively, with gradually sloped perimeters to facilitate establishment of hydrophytic vegetation.
An upland buffer would be created contiguous to the riparian zone to minimize effects of adjacent land use and create a more diverse ecozone. The buffer would be at a greater elevation to support more drought resistant species. The average width of the buffer would be 150 feet, encompassing an area of approximately 11 acres. Revegetation would be utilized to accelerate and ensure native plant establishment. This will minimize the establishment of non-native species, such as salt cedar and arundo donax. Revegetation will involve the use of pole cuttings, containerized plant materials, and native seed mixes. Approximately 163 acres will be revegetated within the basin site as a part of this project.
During the l2-month establishment period, irrigation would be maintained, as well as on-site maintenance efforts to prune trees replace lost and damaged plants, apply fertilizer, apply soil amendments where needed, and prepare status/progress reports. Annual maintenance of vegetation would not be required. Sediment removal is expected to be required about once every 25 years to restore the excavated area to its intended grade.
A continuous un-maintained vegetated corridor will be established along the entire 7-mile length of' Murrieta Creek Channel. The width of the corridor will vary from 20 to 50 feet within the narrowest areas in Old Town Temecula, opening up to widths averaging 150 to 1 75 feet through the less developed stretches of' channel through the City of Murrieta. In some instances the widths of the proposed vegetated corridors are more than twice as wide as the channel as it exists today.
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RECREATION
There is currently a serious need for recreation opportunities within the cities of Murrieta and Temecula. One of the issues brought up in the public involvement effort, was that of opportunities to provide trails, wildlife viewing areas, and other features which would provide a sense of connection between the residents and their environment. To that end, many opportunities were examined to provide recreation in association with flood control and ecosystem restoration efforts. The Recreation Plan portion of the plan was formulated to provide a maximum of benefit and recreational diversity within the same provided acreages provided by flood control construction. Formulation of recreation alternatives involved coordination with the local sponsor, interested agencies and individuals in the study area. There is a significant recreational opportunity provided by the Recommended Plan given that the lands provided at the basin site and upstream, and along the channel access roads.
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DESCRIPTION OF THE RECREATION PLAN
The Recommended Plan for recreation would make use of the southeast comer of the 270-acre detention basin site to create a 49-acre public park. The park would include a children's play area, shade structures, parking, comfort station, barbecues, open space, walks, 4 ball fields and 4 soccer fields, security lighting, and room for additional activities. Located on higher ground within the detention basin, the park site would serve a double purpose by helping to attenuate peak storm flows during times of very heavy runoff. The park, separated from the main body of the detention basin by rounded earthen berms, would experience ponding only on very rare occasion.
Small footbridges across both Murrieta Creek and Santa Gertrudis Creek would also provide links from the park to over 7 miles of trails occupying the banks on either side of Murrieta Creek Channel. The trails will be utilized for hiking, horseback riding, bicycling, and other activities such as bird watching.
The Corps determined that the recommended plan provides $887,900 in total annual benefits, at a benefit cost ratio of 2.7. The total cost of the recreation plan element of the overall Recommended Plan for flood control, environmental restoration, and recreation is $4,450,000.