{"id":581255,"date":"2026-01-16T16:10:00","date_gmt":"2026-01-16T16:10:00","guid":{"rendered":"https:\/\/www.esri.com\/en-us\/industries\/blog\/?post_type=blog&p=581255"},"modified":"2026-01-20T16:07:04","modified_gmt":"2026-01-20T16:07:04","slug":"deep-learning-assessment-in-the-santa-ana-river-watershed","status":"publish","type":"blog","link":"https:\/\/www.esri.com\/en-us\/industries\/blog\/articles\/deep-learning-assessment-in-the-santa-ana-river-watershed","title":{"rendered":"Deep Learning Arundo donax (Arundo) Assessment in the Santa Ana River Watershed"},"content":{"rendered":"

Authored by: Peter Vitt, Senior GIS Project Manager, Santa Ana Watershed Project Authority<\/em><\/p>\n\n

The Santa Ana Watershed Project Authority (SAWPA) was formed in 1975 as a Joint Powers Authority under California law. SAWPA\u2019s mission is to develop and maintain regional plans, programs, and projects that protect the Santa Ana River (SAR) Watershed while maximizing the beneficial uses of its water resources in an economically and environmentally responsible manner.<\/p>\n\n

A longtime threat to the SAR Watershed\u2019s water resources is the invasive plant species Arundo<\/em>. Arundo<\/em> is an invasive grass species pervasive in the stream channels of the SAR Watershed. It was likely introduced to the watershed for erosion control along irrigation channels. Arundo<\/em> is problematic because it uses a lot of water, replaces native habitats, and presents a fire hazard due to its very dense growth pattern.<\/p>\n\n

A study by the California Invasive Plant Council (Cal-IPC) in 2011 estimated approximately 1,400 acres of Arundo<\/em> within the watershed. Past and present Arundo<\/em> removal efforts conducted by Resource Conservation Districts and other agencies have removed significant amounts of the plant from the watershed. But because of the dense root structure and fast-growing nature of the plant, it is difficult to eradicate. Since it had been nearly 15 years since the last Arundo<\/em> estimate was conducted, SAWPA wanted to do a watershed-wide assessment to evaluate the current magnitude of the problem and get an idea of how effective ongoing removal efforts have been in reducing its presence.<\/p>\n\n

Challenge<\/h2>\n\n

The watershed is very large and encompasses approximately 2,800 square miles across four counties in Southern California, including western Riverside and San Bernardino Counties, northern Orange County, and a slice of southeastern Los Angeles County. Because of the watershed\u2019s large size, SAWPA did not have the time or resources to do field investigations, and digitizing Arundo<\/em> plants from aerial imagery across such a large area would not have been accurate or timely.<\/p>\n\n

Solution<\/h2>\n\n

The solution was to employ Esri\u2019s deep learning tools in ArcGIS Pro to identify Arundo<\/em> on imagery and limit the assessment area to places where Arundo<\/em> was likely present.<\/p>\n\n

Identify Areas for Analysis<\/strong><\/p>\n\n

Areas for analysis included those where Arundo<\/em> was most likely to be found and where it has historically been found in the watershed. These included:<\/p>\n\n