After reading through the comments on the previous post – I did a little digging and found this article from the USGS regarding watersheds. Here is the full article: What is a Watershed? I like how the USGS specifically calls out Georgia below and its famous clay soil (bolded below).
Infiltration: When rain falls on dry ground, some of the water soaks in, or infiltrates the soil. Some water that infiltrates will remain in the shallow soil layer, where it will gradually move downhill, through the soil, and eventually enters the stream by seepage into the stream bank. Some of the water may infiltrate much deeper, recharging ground-water aquifers. Water may travel long distances or remain in storage for long periods before returning to the surface. The amount of water that will soak in over time depends on several characteristics of the watershed:
- Soil characteristics: In Georgia, clayey and rockey soils of the northern areas absorb less water at a slower rate than sandy soils, such as in Georgia’s Coastal Plain. Soils absorbing less water results in more runoff overland into streams.
- Soil saturation: Like a wet sponge, soil already saturated from previous rainfall can’t absorb much more … thus more rainfall will become surface runoff.
- Land cover: Some land covers have a great impact on infiltration and rainfall runoff. Impervious surfaces, such as parking lots, roads, and developments, act as a “fast lane” for rainfall – right into storm drains that drain directly into streams. Flooding becomes more prevalent as the area of impervious surfaces increase.
- Slope of the land: Water falling on steeply-sloped land runs off more quickly than water falling on flat land.