Effects of controlled burning of chaparral on streamflow and sediment characteristics, East Fork Sycamore Creek, central Arizona

The effects of controlled burning of part of a chaparral-covered drainage basin on streamflow and sediment characteristics were studied in the upper reaches of the Sycamore Creek basin in central Arizona. A paired-watershed method was used to analyze data collected in two phases separated by the controlled burning of 45 percent of the East Fork Sycamore Creek drainage basin by the U.S. Forest Service on October 31, 1981. Statistically significant increases in streamflow in East Fork occurred from October 26, 1982, through August 25, 1984. Streamflow for August 26, 1984, through the end of data collection for the study on May 31, 1986, was generally at or less than preburn levels. An increase in the percentage of time that flow occurred in East Fork was noted for water years 1983 and 1984. No increase in the magnitude of instantaneous peak flows as a result of the burn was discernable at statistically significant levels. Suspended-sediment yields computed for data collected during water year 1983 were significantly greater in the East Fork drainage basin, 546 tons per square mile, than in the West Fork drainage basin, 22.6 tons per square mile. Suspended-sediment yields computed for East Fork and West Fork for water year 1985, 38.3 and 13.3 tons per square mile, respectively, were much closer in yield. These more uniform yields indicate a possible return to preburn conditions. Data collection did not begin until 11 months after the burn; therefore, the largest increases in streamflow and sediment yields, which commonly occur during the year after a burn, may not have been measured. During the second through fourth years after the burn, smaller increases in stream- flow and sediment yields were found in this study than were found in similar studies in this region.