Which mechanism causes increased flood risk when an alluvial fan experiences rapid urbanization?

💡 Explanation

When alluvial fans are urbanized, reduced infiltration occurs because impermeable surfaces prevent water from seeping into the ground, increasing the volume and rate of surface runoff directly into channels. Therefore, increased flood risk results, rather than incision, changed evapotranspiration, or channel straightening which affect sediment or flow dynamics differently.

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