What has significantly increased impervious surfaces in watersheds?

Urbanization and development are the primary drivers behind the significant increase in impervious surfaces within watersheds. As cities expand and more land is developed for residential, commercial, and industrial use, natural landscapes are altered to accommodate roads, buildings, parking lots, and other infrastructure. These developments create surfaces that do not allow water to infiltrate into the ground, thereby increasing runoff and leading to various issues related to erosion, sedimentation, and water quality.

This transformation of land is critical to understanding how impervious surfaces impact local hydrology. The increase in runoff can overwhelm drainage systems, lead to flooding, and contribute to the degradation of water resources through increased sediment and pollutant loading. In contrast, agricultural activities, natural disasters, and reforestation efforts do not directly contribute to the dramatic rise in impervious surfaces in the same way that urbanization and development do. Agricultural activities may lead to soil compaction and changes in land use, but they don't typically create impervious surfaces like urban development does. Natural disasters can temporarily alter landscapes, but they are often not a consistent factor in the increase of impervious areas. Reforestation efforts generally aim to restore natural cover, which can actually reduce impervious surfaces and promote absorption and filtration of rainwater.