Sediment Production from a Chaparral Watershed in Central Arizona

Abstract

Sediment production from two chaparral watersheds in central Arizona during a period of heavy winter rainfall in 1978 was compared with sediment production over a 14-year period (1964-78). Results indicate sediment production from chaparral is primarily the result of seasonal periods of heavy precipitation and runoff and not from ephemeral summer rainstorms. Sediments from 300 acres (122 ha) above a newly constructed stock watering tank were produced within a few days time in the late winter of 1978 at an accelerated annual rate of 41.1 ft /acre (2.9 m /ha). The sediments came mostly from cutting in channel alluvium in upstream tributaries where the sediments are presumed to have accumulated from downslope creep, dry ravel, and overland flow produced by ephemeral, convective rainstorms. The accelerated rate of sediment production was more than 4 times the average annual rate of 9.8 ft /acre (0.7 m /ha) determined from 14 years of cumulative sediment deposits in a stock tank constructed in 1964.