Unforested Riparian Zones

The Indicator

Many ecological benefits are associated with maintaining forest along streams–riparian forest. These include taking up nutrients in ground and surface water flow, as a buffer between streams and adjacent land uses; stabilizing stream banks; shading the water and maintaining its temperature; and providing food and habitat for aquatic and terrestrial animals alike. The presence of unforested riparian areas is an indicator of aquatic and terrestrial system stress within a watershed.

A Geographic Information System (GIS) was used to calculate the amount of forested and unforested riparian zone in each watershed. First a 100-foot stream corridor (buffer) was identified around free-flowing streams mapped by the Maryland Department of Planning (MDP). This information was combined with MDP 1997 land use data showing forested land, and DNR’s Forest Resource Inventory (FRI) of 1991. To calculate the indicator, the combined area of forested and unforested buffer was summed for each eight-digit watershed. Then, the unforested buffer portion was divided by the total available buffer to create the percent of unforested riparian buffer.

Indicator Use

About 35% of Maryland’s streams lack a forested buffer of at least 100 feet in width. Watersheds having high percentages of unforested land in the riparian area bordering streams are potential targets for riparian reforestation. Where unforested riparian buffer areas represent smaller percentages of stream mileage in a watershed, other restoration measures may be more appropriate to achieving water quality and habitat improvement objectives.

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