Seasonal and Storm-Related Aspects of Sediment Yield From a Rapidly Eroding Coal Refuse Deposit in Southwestern Indiana

A 500‐m2 watershed on a deposit of coal refuse was instrumented for measurements of runoff and sediment yield and monitored for 15 months. The range of 42 storm period sediment yields was greater for the watershed as a whole (16 to 3,480 g m−2) than for a 4.65‐m2 portion of interfluve surface (15 to 1,596 g m−2). The ratio of sediment yield values (watershed:interfluve) was not constant. Ratios of about 7:1 occurred in late spring, when gully floors were flushed of colluvium that had accumulated during winter. The ratio remained above 2:1 in summer, when intense runoff caused gully incision. Estimates of annual sediment yield from three reaches of gully (82 to 160 kg m−2 yr−1) are about an order of magnitude greater than an estimate for interfluves (12 kg m−2 yr−1). A correlation analysis indicated that 78% of the observed variance in watershed sediment yield values is associated with characteristics of storm rainfall and runoff.