Soil type can affect the shape of a hydrograph either by steepening or widening. Storm hydrographs shows how rainwater reaches and feeds a river
Porous soils such as sands facilitates infilitration, thus lessening the water reaching the river. This results in broader storm hydrographs (long lag time)
Impermeable & compact soils e.g clays increase runoff therefore more water reaching a river fast. This results in steep hydrographs and a short lag time