Remote Sensing Analysis and Classification of Stormwater and Sewage Runoff in the Tijuana River

Stormwater and sewage runoff plumes are one of the main causes of marine pollution in Southern California and are critical public health and environmental issues. Frequent spills of untreated sewage into the Tijuana River have been documented since the late 1990s. These have been shown to impact areas within the US and Mexico, causing health concerns for beachgoers and residents and increasing the frequency of phytoplankton blooms. Current methods for assessing water quality from the Tijuana River rely on stations, sampling, buoys, etc., sometimes resulting in delays before local public health authorities realize there may be a health risk. Satellite remote sensing represents an opportunity to expand on this monitoring approach by providing more frequent and detailed spatial information about plume characteristics. For example, RapidEye has been available since 2009 and provides daily satellite imagery with high spatial resolution of 5 meters. This study also leverages ESA’s Sentinel-2A/B, and NASA/USGS Landsat-8, in-situ data, as well as outputs from ACOLITE. ACOLITE is a software that processes Landsat 8 and Sentinel 2 imageries for coastal applications. We distinguish between two different types of plumes (sewage and rain induced stormwater plumes) by examining their distinct characteristics, such as plume color, layering effect, flow rate, and spectral information. The results of this study will enable better prediction of the extent, direction, and persistence of the two types of plumes, and ultimately support improved transboundary monitoring of coastal water quality issues across Southern California / Baja California region.