What is the effect of impermeable surfaces like tarmac in urban areas?

Impermeable surfaces such as tarmac significantly affect water runoff in urban areas by increasing the speed at which water moves across the surface. Unlike natural surfaces, like soil or vegetation, which can absorb water, impermeable surfaces do not allow water to infiltrate into the ground. As a result, when precipitation occurs, water is unable to seep into the soil, leading to an immediate increase in surface runoff.

This rapid runoff can lead to several consequences, including increased flooding potential and the loss of natural water filtration, which can degrade water quality in nearby streams and rivers. Furthermore, the swift movement of water can erode channels and alter the natural landscape of waterways.

The other options are associated with characteristics that are contrary to what impermeable surfaces provide. For instance, impermeable surfaces do not aid in groundwater recharge, as they prevent water from filtering through to aquifers. Instead, they redirect water quickly into drainage systems. Similarly, they do not slow down runoff or have no effect; rather, they exacerbate the water movement issue in urban settings. Understanding these dynamics is crucial for managing urban planning and addressing water management within city environments.