Geomorphic Hazards

Abstract

Geomorphic hazards are those that originate at or near Earth's surface and include expansive soils, soil erosion, slope failures, ground subsidence and karst, river channel changes, glaciers, and coastal erosion. Geomorphic hazards are natural processes until they intersect with human activities and settlements. Geomorphic hazards can be natural or be caused/exacerbated by human activities to some degree. Expansive soils involve Vertisols with certain clay minerals or soils with a high gypsum content. They experience shrink‐and‐swell and deep cracking, which damages structures built on them. Soil erosion has been a hazard since the advent of agriculture. Soils are eroded by rainsplash, sheetwash, rills, gullies, and piping. Wind erosion can be important locally. Dust storms are controlled by wind turbulence, aridity, supply of silt‐sized particles, fetch, and land use/land cover. The variables that control slope failures differ from place to place, and from time to time in the same place. Subsidence is a type of mass movement that involves the downward displacement of surface material caused by natural or artificial removal of underlying support (collapse) or by compression of soils (consolidation). Sudden collapse of the ground, forming sinkholes, is more common in karst terrain. Rivers channels change location by meander cutoffs, meander migration, and by avulsion. These changes can occur in the absence of human activities but can be exacerbated by humans through direct manipulation of the channel or through land‐use/land‐cover changes upstream. Glaciers can create hazards for humans in at least five ways. Coastal hazards include erosion and sedimentation by waves and longshore currents. The types of hazards depend on the geomorphic type of coastline: sandy beaches, cliff coasts, deltas, or coral reefs. All geomorphic hazards can be affected by climate change.