A friend who runs cattle on environmental preserve land near Lincoln once told me that he'd observed changes in the ways that his watershed functioned. Because of the increase in impervious surfaces (roofs, sidewalks, blacktop, etc.) in the upper watershed, he felt that his part of the creek system had become "flashier" - that is, during storms, water levels in the lower watershed came up faster and rose to higher levels that before development occurred. Water levels also dropped faster after storm events ended.
This spring, we've been grazing our sheep in a highly urbanized setting. The sheep are grazing open space, generally on slopes, with homes both above and below. We've observed several changes in the water courses that drain these slopes.
First, we're finding wetlands where they probably didn't exist previously. These seeps and springs get their water from irrigation run-off from landscaping. I would imagine that they serve an important function of filtering any impurities in this runoff before it reaches creeks or ponds (or groundwater).
Second, we're finding that relatively minor amounts of rain can create raging torrents. Because storm runoff is concentrated by the storm drain system in the upper watershed, water levels in the natural water courses rise VERY rapidly. The modification of these systems has caused some erosion on the steeper slopes.
As a farmer, I'm always concerned with conserving soil and water resources - without soil and water (and sunlight), we won't have any grass for our sheep to eat. While I applaud efforts to conserve open space and wildlife habitat as part of urban and suburban development, the impacts on this remaining open space are complex. Successful management of these lands is equally complex!