Slide 14 of 75
Notes:
The hydrologic impact of urbanization is not limited to storm events. During dry weather periods, urban streams tend to have less flow because groundwater recharge and stormwater infiltration has been diminished. While streams that have never been developed retain their flow during dry weather conditions, many urban streams lack the baseflow necessary to sustain healthy habitat conditions during extended periods of dry weather.
An increase in impervious surface often decreases the amount of rainfall available for infiltration. Without infiltration, the groundwater will not be recharged and the stream will lose this potential source of water, thus low flows tend to be lower in urbanized watersheds.