Which areas are most conducive to flash flooding?

Hilly areas with steep slopes are particularly conducive to flash flooding due to several key factors associated with topography and precipitation patterns. When heavy rainfall occurs in these regions, the steepness of the terrain can cause water to flow rapidly down the slopes, overwhelming drainage systems and leading to a sudden surge of water in lower-lying areas. The rapid run-off combines with limited infiltration, as the steep ground often prevents water from soaking into the soil, leading to high rates of surface flow.

In contrast, flat plains and agricultural fields may allow water to spread over a larger area, absorbing and draining more slowly, which reduces the intensity of flash floods. Areas with dense forest cover can slow down the flow of water, allowing for greater absorption into the ground. Coastal regions may experience flooding from storm surges and sea-level rise, but this is typically a different phenomenon compared to the rapid onset of flash flooding associated with hilly terrains. Therefore, the characteristics of steep slopes and rapid runoff in hilly areas make them particularly vulnerable to flash flooding, confirming why this is the most appropriate answer.