Urbanization with more impervious surfaces tends to cause which hydrological change in streams?

Urbanization with more impervious surfaces tends to cause which hydrological change in streams?

• A. Lower peak flows
• B. Cooler runoff
• C. Longer lag times
• D. Higher peak flows and flashiness

Answer: (D)

Urbanization with many impervious surfaces changes how water moves across the landscape. Water can’t soak into the ground, so rainfall becomes runoff that is delivered to streams very quickly. That rapid input creates larger and faster increases in stream discharge—a high peak during storms and a flashy, sharp rise and fall in flow. Because the water reaches the stream so fast, the lag time is shorter. In contrast, more infiltration and storage would smooth the response, producing lower peaks and longer lag times. So the scenario most consistent with impervious surfaces is higher peak flows and flashiness.

Urbanization with many impervious surfaces changes how water moves across the landscape. Water can’t soak into the ground, so rainfall becomes runoff that is delivered to streams very quickly. That rapid input creates larger and faster increases in stream discharge—a high peak during storms and a flashy, sharp rise and fall in flow. Because the water reaches the stream so fast, the lag time is shorter. In contrast, more infiltration and storage would smooth the response, producing lower peaks and longer lag times. So the scenario most consistent with impervious surfaces is higher peak flows and flashiness.