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Understanding Sediment Processes of Los Laureles Canyon in the Binational Tijuana River watershed
Yuan, Y., D. Biggs, D. Langendoen, D. Bingner, N. Gudiño, K. Taniguchi, D. Castillo, D. Taguas, D. Liden, AND C. Lin. Understanding Sediment Processes of Los Laureles Canyon in the Binational Tijuana River watershed. Presented at 2015 EGU Conference, Vienna, AUSTRIA, April 12 - 17, 2015.
Presentation of analysis at the EGU Conference in order to ensure that results will be used to make informed land-use decisions that will help protect the environment and human health andto provide data regarding excessive erosion in Tijuana during storms produces sediment loads that bury native vegetation, lock tidal channels, and enter coastal zones to impact wildlife adversely.
Tijuana River Basin originates in Mexico and drains 4465 km2 into the Tijuana River Estuary National Research Reserve, a protected coastal wetland in California that supports 400 species of birds. During storms, excessive erosion in Tijuana produces sediment loads that bury native vegetation and block the tidal channels. It also threatens human life, causing roads and houses in Mexico to collapse and the Tijuana River Valley in the U.S. to flood; government agencies in US and Mexico spend millions annually to remove sediment. The US Environment Protection Agency (USEPA)-SEMARNAT Border 2020 program made reducing sediment to the Tijuana Estuary a high priority. The primary sources of sediment are gully formation on unpaved roads, channel erosion, and sheet and rill erosion from vacant lots in Tijuana (Biggs et al, 2009). Because 73% of the watershed is located in Mexico, the problem is likely to worsen as Tijuana continues to urbanize. USEPA, with support from US Department of Agriculture (USDA), San Diego State University (SDSU), and Ensenada Center for Scientific Research and Higher Education (CICESE), is collecting data to develop a model that stimates sediment loadings in a sub-basin of the watershed (Los Laureles Canyon) for existing conditions as well as future alternative development scenarios. This study also evaluates reduction/prevention of sediment loads from green infrastructure projects, sediment basins, road paving, and conservation easements; the Annualized AGricultural Non-Point Source (AnnAGNPS) and CONservational Channel Evolution and Pollutant Transport System (CONCEPTS) models were used. USEPA/SDSU/USDA/CICESE personnel have conducted or are conducting: 1) rainfall, runoff and sediment monitoring to understand the hydrologic and sediment processes; 2) field sampling to determine channel stability and its contribution to the sediment budget of the study watershed; 3) gully mapping and topographic surveys following storm events to understand gully formation and evolvement; 4) bed and bank material characterization and mapping. Workshops/training on field data collection and model development are ongoing efforts to keep National Water Commission (CONAGUA), the City of Tijuana, and other interested stakeholders informed to ensure that results be used in landuse decisions that will help protect the environment and human health.