Simulated Rainfall Duration and Sequencing Affect Soil Loss

Abstract

ABSTRACT SOIL loss from 99-mm diameter laboratory samples of Hagerstown silty clay loam soil was measured under 55 mm/h simulated rainfall. The soil losses from two aggregate size distributions of the same soil were compared. When rain was applied in different durations, soil loss rates increased rapidly during the period when surface soil aggregates were being broken down by the rain drops. After the period of aggregate breakdown, the soil loss rates decreased and approached a long term constant rate as the soil surface was puddled and compacted by the rain drops. For sequenced rainfall events separated by 24-h drying periods, a series of twelve 5-min rainfall events on the coarse aggregates produced soil loss rates which were 86% greater than the soil loss rates measured from six 10-min rainfall events. Cumulative soil loss from the coarse aggregates which had received twelve 5-min rainfalls was 4.5 kg/m^, compared to 2.8 kg/m^ from the coarse aggregates which had received six 10-min rainfalls. In a series of storms, each event produces an initial high soil loss rate. When each storm is short this initial effect, repeated many times, produces greater soil losses than during longer storms which have fewer initial precipitation periods.