A hillslope steepened to its maximum stable, or threshold, angle. According to the threshold hillslope model, landscapes respond to river dissection into the bedrock by adjusting landslide erosion rates on threshold hillslopes. This model assumes that landslide erosion rates are related to river incision rates, and that landslide erosion rates increase non-linearly as hillslope gradients approach the threshold angle. See DiBiase et al. (2012) ESPL 37, 8, 855. In steady-state landscapes, the threshold hillslope model additionally predicts that landslide erosion rates are spatially coupled with rock uplift and exhumation rates.