CHARACTERIZING HYDROLOGICAL AND GEOMORPHOLOGICAL CHANGES IN URBAN STREAMS THROUGH ENVIRONMENTAL SIGNALS

Characterizing environmental degradation in urban ecosystems is a pressing issue in today’s rapidly developing landscape. Retention ponds, which are human-made water storage ponds intended to store excess urban runoff, are one construction measure used to mitigate degradation from hydrological changes. Strawberry Creek is a small stream system located in James City County, Virginia that has been heavily impacted by the failure of a near-by retention pond to accomplish natural water release, leading to significant geomorphological and hydrological changes over the past two decades and quickly degrading the ecosystem. Erosion has been quickened by the loose soils of Strawberry Creek, with underlying formations including loose sands, silts, and clays from the Windsor, Bacon’s Castle, Sedley, St. Mary’s, and Yorktown Formations. The goal of this study is to characterize changes in the geomorphology and hydrology of the stream downstream of the retention pond by using signals from trees, which were measured using two indicators: leaf area index and tree rings. Leaf Area Index (LAI) data was collected using the LP-80 ceptometer along both Strawberry Creek and an unimpacted stream that merges with Strawberry Creek. The LAI results are presented for different sections of the stream system with comparisons between the variation in impacted versus unimpacted stream areas. Variation in overall LAI is greater for the stream sections impacted by the retention pond. Tree cores were collected from beech trees in three primary settings along the stream: unimpacted trees from the hillslopes, trees partially buried by eroded upstream sediments on the stream banks, and trees heavily impacted by erosion through uprooting or burial within the stream channel. Tree rings were measured to investigate the timing and magnitude of changes in tree growth as indicators of geomorphological changes to the stream channel. Overall, this research seeks to improve our understanding of geomorphological and hydrological changes in urbanized landscapes by leveraging trees as readily available environmental sensors.