Utilizing GIS to Study Concentrated Flow Off Agricultural Fields in the Chesapeake Bay Watershed

Hello W&M!  My name is Sarah Young, and I am a Geology and Environmental Science Double Major here at the College.  My Honors Thesis project that I will be working on this summer and next year revolves around the problems associated with agricultural runoff bypassing riparian buffers, allowing excess nutrients into the already unhealthy Chesapeake Bay.  I am so excited to embark on this journey and begin my research with Professor Greg Hancock of the Geology Department.  Many thanks to Professor Hancock, the Charles Center, the Theresa W. Long and Emil L. Hanzevack Faculty/Student Research Endowment, and everyone who has contributed to my Honors research via the W&M website.  I would not have been able to do this without your generous assistance.  I’d also like to recognize Lyndsey Funkhouser, who recently defended her Honors Thesis on riparian buffer bypass and has helped me in crafting a project that would expand on her own.

Agricultural runoff is a significant source of the excess nutrient and sediment pollution in the Chesapeake Bay and its tributaries.  In an effort to alleviate this pollution, the state of Virginia requires all agricultural fields in the eastern-most part of the state alongside streams to have along the edge of the field a vegetated strip of no less than 100 feet, called a riparian buffer.  The purpose of this buffer is to trap nutrients and sediment flowing off the agricultural field in order to increase water quality of the adjacent stream flowing into the Chesapeake Bay.  Ideally, all nutrients and sediment are trapped as flow moves into the buffer, thus preventing them from ultimately traveling to the Bay.  In practice however, several studies have shown that sloped or uneven topography can cause concentrated flow off the field, resulting in significantly decreased buffer effectiveness.  Concentrated flow off the field causes channelization that bypasses the buffer, allowing much of the nutrient and sediment pollution through to the stream and eventually the Bay.  However, this phenomenon has not been widely studied and has not been documented in the literature for the Chesapeake Bay watershed.  In this study, we hope to find a way to accurately predict locations of channelization and buffer bypass using Geographic Information Systems (GIS), slope-area comparisons, and the Vegetative Filter Strip Model (VFSMOD) developed at the University of Florida.

I will be looking at fields in the Virginia Coastal Plain, Piedmont, and Valley & Ridge regions using GIS software and tools within this software to calculate flow accumulation.  Basically, the program will tell me where the most runoff goes when it exits the field.  These areas of concentrated flow can create channels through the riparian buffers bordering the field, allowing much of the nutrient and sediment pollution from the field into the stream.  Eventually, these pollutants will make their way to the Chesapeake Bay, contributing to eutrophication.  This has a variety of consequences, the worst of which being the eventual creation of an anoxic zone with no dissolved oxygen in the water, meaning fish and other organisms can no longer live in that area of the Bay.

I believe this project will increase our understanding of riparian buffer bypassing, allowing future policy changes to ensure the most effective buffers possible so excess nutrients do not reach the streams bordering agricultural fields.  If you would like to know more about my research or have comments/questions, please feel free to post them below!  I want my research to be as accessible as possible, so I will be updating my blog about it periodically throughout the summer.  Thank you for your interest!