Deep critical zone controls on shallow landslides

Shallow landslides typically involving just the soil mantle constitute both a primary process driving landscape evolution and a significant geologic hazard.  Theory for and empirical documentation of shallow landslides generally assumes that the elevated pore pressures that destabilize soils arise from runoff just within the soil.  In many landscapes, however, it has been recognized that groundwater emerging from underlying weathered bedrock can generate destabilizing pore pressures.  Here, we develop a coupled hydrologic and slope stability model that explicitly explores how a conductive bedrock weathering zone guides storm runoff and localizes shallow landslides across a watershed.  Our findings suggest that first-order variations of deep CZ can provide physical explanations for variations observed in the susceptibility, magnitude, and timing of shallow landslides, and that CZ structure may be inferred from patterns and timing of landsliding.