Which mechanism causes increased flood risk to structures built on alluvial fans at the base plains of mountains?

💡 Explanation

When sediment load exceeds transport capacity, channel avulsion occurs due to the aggradation and blockage of one flow path on the alluvial fan, leading to a new, often unpredictable channel forming across structures. Therefore channel avulsion results, rather than subsidence, liquefaction, or deflation which involve entirely different drivers.

• Which mechanism causes the formation of terraced alluvial fans in arid environments after prolonged tectonic uplift?
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• Which risk increases when artificial levees constrict a river's floodplain during an extreme rainfall event?
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• Which long-term isostatic process elevates previously submerged fjord landscapes?
• Which geological feature’s formation follows the cutoff of a river meander loop alongside a floodplain lake?