Joint Control on Stream Direction and Pothole Axis Formation in the Lower Chesapeake Group, southeastern King William County, Virginia

Multiple heavy rain events in the last few decades, three in particular: Hurricane Isabel (2003), Tropical Depression Gaston (2004), and Hurricane Irene (2011), produced noteworthy downcutting of numerous streams in two adjacent watersheds in the Virginia Coastal Plain in southeastern King William County, Virginia. The downcutting has exposed joint sets in the Chesapeake Group clays in streambeds with yellowish gray clay, as well as a series of potholes in a streambed with a blueish gray clay. The objective of this study was to test the hypothesis that joints in the streambeds in these two watersheds control stream direction and pothole axis formation. The test showed an agreement of joint strike directions with stream directions, and a relationship between the axis of the potholes and stream directions in the Pothole Stream. Overall, results indicate that the stream directions from the three streams and the axis of the potholes in the Pothole Stream in the study are controlled by the strike of joints in the two watersheds.