4.2 Aquatic Communities
4.2.9.3 Problems Affecting Habitats Medium river communities in North Carolina have been threatened by a variety of per- turbations in the past, similar to threats to small and large rivers, and many of those same threats continue today. Land Use. Converting land uses from natural forest to agriculture or silviculture produc- tion and residential and commercial development continues to threaten stream integrity. Deforestation and increased impervious surfaces cause increases in sedimentation, bank erosion, and stormwater runof containing sediment and other pollutants. Erosion and the resultant sedimentation are the largest sources of nonpoint source pollution in most aquatic systems. Te increased loads could afect water quality and habitat for aquatic spe- cies, as well as drinking water supplies for municipalities (Band and Salvesen 2009) . Sources of erosion include disturbance from development activities and agriculture. Residential development can increase erosion during the construction process, but also as a secondary result of increased impervious surfaces in the watershed. Most watersheds in the Piedmont are already highly developed and development pressure is likely to increase in the Coastal Plain, which will lead to an increase in impervious surfaces, increasing runof, stream and bank erosion, pollution inputs and increased fashiness of rivers. An increase in impervious surfaces due to roads, parking lots, homes, and businesses increases the amount and speed of runof being delivered into aquatic systems. Decreased groundwater recharge between storms due to impervious surfaces leads to a decrease in stream base fows. Riparian vegetation is critical to overall stream and streambank stability and moderation of water temperatures. Lack of riparian vegetation or inadequate width of forested bufers can cause streambank erosion and sedimentation. In addition to stabilizing streambanks, riparian vegetation contributes nutrients to the stream community, provides large woody debris that increases habitat complexity, and helps regulate stream temperature by pro- viding shade. Lack of sufcient vegetation cover contributes to rising water temperatures, especially where water depths are shallow enough that the entire water column is subject to solar heating. Impoundment. Dam construction on medium rivers has altered hydrology and morphol- ogy. Many rivers that were once free-fowing are now dammed, severely fragmenting habi- tat and often isolating populations of aquatic species above and below the impoundments. Indirect efects to portions of the system downstream of dams include disruption of natural hydrologic and thermal regimes. Increases in water surface area of impoundments and the resulting increases in evaporation rates, in addition to water withdrawals, reduces the amount of water available downstream. Low DO levels can also impair waters downstream of dams.
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2015 NC Wildlife Action Plan
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