Special Threats and Challenges for the Big Laurel-Whitetop Laurel Creek Watershed

Two important special threats and challenges facing the Big Laurel Creek – Whitetop Laurel Creek watershed are increased development and land use changes and habitat fragmentation particularly aquatic habitat. 

The first special threat and challenge facing the watershed is continued and potentially increased residential and commercial development, with the resulting land use changes.

An example of the changed hydrological response of a watershed to increased development and urbanization can be seen on this typical hydrograph.  As the ground cover is changed from more to less permeable (such as forest to farmland or pasture, and farmland and pasture to houses, asphalt and concrete roads) the storm water response changes from a extended, gentle flow to a short, very destructive high flow.

                 Courtesy of https://www.slideserve.com/buzz/an-introduction-to-benthic-macroinvertebrates, slide 7

Quoting from the article, “Water Resources and Land Use and Cover in a Humid Region: The Southeastern United States” (Nagy et al, 2011) ,  “It is widely recognized that forest and water resources are intricately linked. Globally, changes in forest cover to accommodate agriculture and urban  development introduce additional challenges for water management. The U.S. Southeast typifies this global trend as predictions of land-use change and population growth suggest increased pressure on water resources in coming years. Close attention has long been paid to interactions between people and water in arid regions; however, based on information from regions such as the Southeast, it is evident that much greater focus is required to sustain a high-quality water supply in humid areas as well. … Commonly, forest removal leads to increased stream sediment and nutrients, more variable flow, altered habitat and stream and riparian communities, and increased risk of human health effects.”

The Big Laurel Creek – Whitetop Laurel Creek watershed was likely totally forested prior to European settlement in the 1700s.  Since that time, the watershed's land use, land cover and hydrologic response has been permanently altered by settlement and gradual urbanization.  This has resulted in a net negative impact on the overall pre-settlement health and function of the watershed.   

Also unique to the Big Laurel Creek – Whitetop Laurel Creek watershed is that the headwaters in the higher elevation and the final outflowing sections are under US Forest Service control and remain in heavily forest, and wilder condition, while the intervening floodplain section has been fully developed into residential houses, pasture lands and farmland.

The second special threat and challenge facing the Big Laurel Creek – Whitetop Laurel Creek watershed is habitat fragmentation, particularly aquatic habitat.  Due to topography of the mountain valley of the watershed, with the only relatively flat land naturally occurring in the stream’s floodplain, human land use changes and infrastructure development has fixed the topographical features into a condition that can not respond to environmental changes.  

With the meandering of the stream and the need for relatively straight roads, there are many stream-road crossing in the watershed.  The Nature Conservancy (TNC) has recently completed an aquatic organism passage (AOP) assessment of the Big Laurel Creek – Whitetop Laurel Creek watershed.  Significant barriers are indicated by the larger circles shown on this GIS map.

An example of the impact of an AOP barrier is illustrated for the large concrete box culvert on Virginia State Route (SR) 612 at the lat long location of 36.67 N, 81.62 W (36.6696, -81.6190).  As seen in the photograph, the vertical height of the bottom of the culvert and the natural stream bed is too high for most aquatic organisms.  As a result, 12.8 square miles of habitat, or 23% of the total the Big Laurel Creek – Whitetop Laurel Creek watershed, has been cut off for native aquatic life. 

References:

• 1.    Nagy, Chelsea and Lockaby, Graeme & Helms, Brian and Kalin, Latif & Stoeckel, Denise. (2011). Water Resources and Land Use and Cover in a Humid Region: The Southeastern United States. Journal of environmental quality. 40. 867-78. DOI:10.2134/jeq2010.0365
• 2.    Connections between Forested and Urban Landscapes and Implications for Water Supply, Ecosystems Land Change Science Program December 13, 2018, https://www.usgs.gov/programs/ecosystems-land-change-science-program/science/connections-between-forested-and-urban