Effects of large deep-seated landslides on hillslope morphology, western Southern Alps, New Zealand

摘要: [1] Morphometric analysis and air photo interpretation highlight geomorphic imprints of large landslides (i.e., affecting ≥1 km2) on hillslopes in the western Southern Alps (WSA), New Zealand. Large attain kilometer-scale runout, affect >50% total basin relief, 70% are slope clearing, thus relief limiting. Landslide terrain shows lower mean local variability, angles, steepness, concavity than surrounding terrain. Measuring angle smoothes out landslide morphology, masking any relationship between possible threshold hillslopes. failures also occurred low-gradient slopes, indicating persistent low-frequency/high-magnitude hillslope adjustment independent fluvial bedrock incision. At scale, slope-area plots partly constrain effects process regimes. gradually blend with characteristics at orogen scale (102 km), while being sensitive to length scales failure, topography, sampling, digital elevation model resolution. This limits means automated detection, underlines importance morphologic contrasts for detecting WSA. controls low-order drainage include divide lowering shifting, formation headwater basins hanging valleys, stream piracy. Volumes typically mobilized, yet still stored numerous deposits despite high denudation rates, >107 m3, theoretically equal 102 years basin-wide debris production from historic shallow landslides; lack absolute ages precludes further estimates. Deposit size mature forest cover indicate residence times 101–104 years. On these timescales, require attention landscape evolution models tectonically active orogens.