Belmont Creek Watershed Study: Alternatives for a Sustainable Watershed
WRECO, in cooperation with a major pharmaceutical company, has developed an original hydrologic and hydraulic model that will help the various stakeholders in the Belmont Creek watershed with flooding and stormwater management. This effort is an example not only of using modelling to describe a complete watershed, but of broad collaboration between industry, municipalities, and regulatory agencies.
Belmont Creek, located in San Mateo County, is subject to periodic flooding during relatively small storm events. This flooding can halt the pharmaceutical company’s local manufacturing operations. Many solutions have been tried, including local dredging and floodgates at all entrances, but no sustainable solution has been found to alleviate the problem. The majority of opportunities are in the City of Belmont with the benefits from these opportunities occurring in other jurisdictions--a dynamic that has hindered previous actions to solve flooding issues. The pharmaceutical company and WRECO have reached out to stakeholders including the San Francisco Bay Regional Water Quality Control Board, the California Department of Fish and Wildlife, the City of Belmont, the City of Redwood City, the City of San Carlos, Caltrain, San Mateo County, and the California Department of Transportation (Caltrans). Rather than focusing on the local flooding that occurs on their property during storm events, the pharmaceutical company/WRECO team realized the importance of having a larger understanding of the entire Belmont Creek watershed and bringing the community together to find solutions to not only alleviate inundation, but also look for avenues to pursue water quality and habitat improvements.
This presentation will focus on the four alternatives studied for watershed improvement and peak runoff reduction chosen by the stakeholders including dredging operational improvement at Water Dog Lake that will decrease erosion potential downstream; floodplain improvements at Twin Pines Park that will decrease sedimentation, restore creek habitats, provide overland storage, and increased infiltration for nuisance flows; culvert improvements and bypasses downstream that will create underground storage, increased conveyance with potential for long-term LID measures for land use planning; and tidal gates downstream that will provide flood storage for the tidal prism during storm events and negate the effects of tidal backwater to the creek.
The model includes field data gathered through creek walks assessing the fluvial geomorphology and erosion potential; creek sediment and water sampling to assess areas of potential improvement in terms of flood control, water quality, and habitat; rainfall and creek flow data collection; and surveys. Using this collected data, WRECO developed a hydrologic model using GIS and the U.S. Army Corps of Engineers’ (USACE) HEC-HMS, breaking down the watershed into subbasins that could be later applied to the hydraulic model at different points along the creek path. The hydraulic model was developed using the USACE HEC-RAS program; it breaks down the creek into different reaches to get a better understanding of the different hydraulic changes the creek in different areas to assess its impacts across the watershed as a whole.
This collaboration has provided an open forum where all stakeholders can voice their opinions and comments on the watershed model’s development and provide realistic options on potential alternatives that can be constructed to improve the watershed functions. This project stands as an example of developing regional stormwater management tools through communal cooperation.