Quantifying sediment source contributions in an agricultural catchment with ephemeral and classic gullies using 137Cs technique

•The fallout 137Cs was used to quantify the sediment source at various spatial scales in agricultural catchment.•Contributions of subsoil for the catchment with classic gullies were greater than those with ephemeral gullies.•The eroded fine sediment of the catchment mainly came from gully erosion.•Soil conservation measures should be concentrated on stabilizing gullies.