Infiltration

Prolonged hot, dry conditions can harden the soil surface and reduce infiltration. Where this happens, more rain flows over the surface and reaches the channel quickly, increasing discharge and potentially causing renewed erosion or flooding.

Geology and soil type: permeable ground encourages infiltration and slower movement through the soil and rock. This tends to lengthen lag time and reduce peak discharge. Poorly permeable ground, including clay-rich soil, restricts infiltration.