Wildfire-streamflow interactions in a chaparral watershed

The 272 km(2) Malibu Creek watershed in the Santa Monica Mountains of southern California was chosen to study the impact of wildfires on streamflow. The predominant plant community in the Malibu Creek watershed is the chaparral, a fire-prone vegetation, which has experienced 10 large wildfires since 1949. Post-fire vegetation succession in the Malibu watershed indicates long-term vegetation changes that have heightened the likelihood of wildfire incidence in the last few decades. Precipitation, streamflow, and wildfire data from 1949 to 1994 were analyzed to determine the effect of vegetation burning on catchment streamflow. A paired-catchment analysis allowed the reconstruction of the expected natural streamflow in Malibu Creek in fire-impacted years. A comparison of measured and reconstructed streamflows showed annual streamflow increases up to 20-30% in fire-impacted water years relative to non-fire years. A statistically significant difference between the mean streamflow in fire and non-fire years was also established by means of the Wilcoxon test. (C) 2001 Elsevier Science Ltd. All rights reserved.