Paper No. 5
Presentation Time: 9:05 AM
RIVER TERRACES, INCISION AND POST-GLACIAL LANDSCAPE EVOLUTION IN SOUTHERN NEW ENGLAND
River terraces are ubiquitous throughout the southern New England landscape. These features demonstrate the role of glacio-isostatic rebound, local and regional base level changes, rock strength, climate change, and anthropogenic effects that have played during the post-glacial evolution of rivers in this region throughout the late Pleistocene and Holocene. Despite their abundance, previous studies in New England concerning fluvial terraces are limited. However, due to recent advances in GIS mapping techniques and availability of high-resolution data (e.g. LiDAR), we can expand the mapping and interpretations of these fluvial features. Here, we present a contribution to New England fluvial geomorphology through an analysis of fill and cut fill terraces found adjacent to the Farmington, Housatonic and Thames Rivers in Connecticut, the Deerfield and Westfield Rivers in Massachusetts, and the Connecticut River in southern New England. We use high-resolution airborne LiDAR data to map the distribution and heights of terraces along these rivers, and combine this topographic analysis with fieldwork, trenching and analysis of archeological records. Pairing our mapping with age constraints on the formation and timing of abandonment for various terrace levels allows us to address the timing and style of post-glacial incision. Our results indicate there are typically one to three terrace levels preserved along all reaches of these rivers, but maximum terrace heights vary, with heights up to 25 meters above the modern active channel for the Farmington River, 18 meters for the Housatonic River, 22 meters for the Thames River, and 32 meters for the Connecticut River. Terraces heights also demonstrate systematic variations along stream. Some rivers in our dataset (Thames, upper Farmington) display a widespread and uniform amount of incision beneath a consistent high terrace level, while others (Housatonic, lower Farmington, Connecticut) highlight the control of bedrock knickpoints. These knickpoints slow the propagation of incision and lead to higher terrace heights downstream of knickpoints than upstream.