Why can deforestation along river banks increase flood risk?

Correct answer: Trees slow runoff and bind soil

The direct answer is A: trees slow runoff and bind soil. Vegetation along a river bank catches rainfall, slows the movement of water over the ground, helps water enter the soil and holds soil with its roots. These effects reduce rapid runoff, bank erosion and the amount of loose sediment entering the river. Without trees, water can move faster and soil can wash away, which may increase flood risk, although floods also depend on rainfall, drainage and river capacity. Option A correctly gives the physical chain. Option B is wrong because trees do not normally make freshwater saline. Option C is wrong because river-bank trees do not stop ocean tides. Option D is impossible and unrelated to river processes. Memory cue: roots hold soil and vegetation slows water.