Monitoring the recovery of streams in the San Gabriel mountains (CA) following the largest wildfire in Los Angeles county history: Station fire - 2009

The September 2009 Station Fire was the largest wildfire in Los Angeles County’s history, burning 161,189 acres or 252 square miles of upper watershed mountainous terrain in the Los Angeles River watershed and a small portion of the San Gabriel River watershed. The areas affected by the fire had not burned for decades, resulting in an extremely hot burn that devastated the riparian zones of streams throughout the upper watersheds. The following winter, several rain storms caused widespread erosion from the burn areas. Prior to the fire, the Los Angeles River Watershed Monitoring Program (LARWMP) and San Gabriel River Regional Monitoring Program (SGRRMP) had initiated ambient water quality monitoring programs using randomly selected sites where a suite of indicators including water chemistry and toxicity, bioassessment and physical habitat conditions, were collected annually during the summer. Several of these sites burned during the Station Fire, providing an opportunity for the SGRRMP and LARWMP to establish long term trend monitoring programs at these sites in an attempt to detect the rate and quality of their recovery.   

Biological conditions, as measured by the Southern California Index of Biological Integrity (SoCA IBI), decreased immediately following the fire to levels below the impairment threshold at some sites and have gradually begun to improve. In contrast, measures of the riparian habitat condition using the California Rapid Assessment Method (CRAM), showed clear decreases in riparian zone biotic structure, increases in eroded and vulnerable banks, and decreased streambed complexity and structure. It is hoped that the results of this monitoring effort will provide forest service managers with the information they need to help them to efficiently manage the recovery of burn areas in these watersheds in the future.