ABSTRACT
The effects of forest fires on watershed hydrology have been well documented, but quantitative information on parameter properties that govern runoff are limited. The Cerro Grande Fire burned approximately 19,800 ha including the headwaters of the major watersheds that cross Los Alamos National Laboratory during May 2000. The location of gauging stations below the burned areas presented an opportunity to assess hydrologic response and model parameters governing runoff following the fire. The Curve Number technique was used to estimate runoff both before and after the fire, and this method is used throughout the United States to assess post-fire hydrologic response. Peakflow rates are another indicator of fire impacts. Starmer Gulch, a small watershed, was a headwater stream that had a complete record following the fire, and data from Starmer Gulch was used to examine Curve Number and peakflow behavior. Ten rainfall events were measured over the period from 2000-2004. The small number of events is due to the drought that was occurring in the region. Analysis of the Curve Number reveals from adjacent watershed before the fire indicated a very sluggish response. The Starmer Gulch results indicated the expected change in magnitude of the Curve Number, but it is difficult to determine if watershed response had changed that much. The peakflow rates did show an approximately 3-orders-of-magnitude change from pre-fire values. All of the measured rainfall events were less than 10-year return period for the 30-minute maximum intensity of these storms. A decline in peakflow rate was seen for the period with values only an order of magnitude above the pre-fire values in 2002. This is an example of an extreme land-use change, and more analyses of these conditions are needed to develop the database needed to enhance capabilities for post-fire assessments.