Paper No. 9-29
Presentation Time: 8:00 AM-12:00 PM
IDENTIFYING THE RELATIONSHIP BETWEEN LARGE DISCHARGE EVENTS AND THE TRANSPORT OF WOODY DEBRIS ON THE WHITEWATER RIVER, INDIANA
Large woody debris (LWD) is critical to the health and function of stream systems and integral to stream restoration design. LWD, consisting of wood >10cm in diameter and >1m in length, influences habitat structure, flow patterns, sediment deposition, and pool formation. Although much work has been done on the role of LWD in streams in the western U.S., few studies have been conducted in the Midwest and the Ohio River Valley, in part due to the limited supply of LWD. The Whitewater River in southeastern Indiana, however, has a wide riparian corridor and few dams or bank stabilization measures, allowing for the recruitment and transport of LWD. This study aimed to link the mobility of LWD to stream discharge and stream height through multiple surveys conducted on the Whitewater River. Jams were monitored using historic records and satellite imaging to spot any fluctuations of LWD. To determine the required discharge for mobilization, LWD was compared to various flood events. Log jams were surveyed and inventoried on the Whitewater River from Metamora to Brookville, Indiana from May 30, 2021 to June 01, 2021. Log jams were categorized on their position (meander, bar apex and bar top jams) and the number of large structural logs (i.e. key members) contained. During the previous four years a much longer reach from Metamora to where the Whitewater River joins the Great Miami River (~45km) was also surveyed for lag jams. The flood events of 2018 and 2019 saw the biggest changes in terms of key members and the largest annual average discharge. The evidence suggests movement of single pieces of LWD and small jams occured during annual flood events, whereas the mobilization of larger jams requires bankfull discharge events or larger. The Whitewater River runs through heavily cultivated lands in southeast Indiana and southwest Ohio and receives heavy loads of sediment and nutrient pollution as a result. As efforts increase to improve water quality in the Ohio River Valley, it will be important to integrate LWD in stream restoration design. Understanding its mobility will be key in developing this design.