Estimating the debris-flow magnitude using landslide sediment connectivity, Qipan catchment, Wenchuan County, China

•Landslide connectivity has a significant negative relationship with the area and location.•The connectivity evolution of landslides has a positive effect on the supply capacity from landslides to debris flows.•An integrated method is proposed to estimate the debris-flow magnitude.•The average error of magnitude estimation is<20% when considering landslide connectivity.