Steeper landscapes tend to erode faster. In this study, we also find that sediment produced on steeper landscapes is coarser. Soils are coarser because fragments spend less time in the soil so are less exposed to processes that can break them down. Change in sediment sources impact the sediment transported by rivers: rivers transport sediment up to cobble size in low-slope, soil-mantled areas; they transport much coarser sediment (including boulders supplied from landslides) in the steep areas.