Land Use and Land Cover Effects on Runoff Processes: Agricultural Effects

Abstract

Abstract The impact of agriculture on runoff processes cannot be underestimated. The greatest impact is usually on soil surface conditions, specifically infiltration. Undisturbed soils have much higher infiltration capacity than soils in agricultural land. Once cultivated, soils become easily compacted as they are laid bare to the elements until the next crop develops a protective cover. Infiltration can fall to levels where infiltration‐excess overland flow can occur even in rainfall of modest intensity. Successive rainfall events compact the bare soil further and impermeable crusts often form. Heavy machinery used in agriculture exacerbates soil compaction, particularly at depth, via the development of plough pans. These compacted, dense layers have significantly higher bulk density and lower total soil porosity than the soil directly above or below it and frequently become preferential zones of runoff generation. Temporary saturation of shallow topsoil layers leads to topsoil saturation overland flow that, if connected to the channel network, may become a significant contributor to event response. Linear zones of compaction and reduced hydraulic conductivity that occur as a result of vehicular traffic have similar impacts.