COMPARING THE EFFECTS OF BEAVER DAMS AND ARTIFICIAL DAMS ON SEDIMENT DISTRIBUTION IN LOW-GRADIENT STREAMS IN MASSACHUSETTS

Blockages in stream flow, both natural or anthropogenic, can have effects on a number of stream characteristics, such as velocity, discharge, and sediment distribution. The goal of this study was to determine if different types of stream discontinuities, in particular, beaver dams and artificial dams, yielded differences in sediment distribution in small, low gradient New England streams. Field studies were conducted in four headwater watersheds in Massachusetts, between June 2014 and September 2014. Channel morphology and wood distribution in the channel and floodplain were measured with a Leica TPS total station. Longitudinal profiles, bed grain size, channel cross-sections, and a wood survey were collected along two to three reaches within each watershed. A Wolman pebble count was completed at each reach, measuring 300 pebbles. The reaches located in watersheds with beaver activity tended to have higher D₈₄ values than those with artificial dams. When comparing D₈₄ to average bankfull shear stress, there were no consistent overall trends. Preliminary grain size analysis did show that the watersheds that had beaver activity (Pearl Hill Brook and Bear Swamp Reservation) had a positive correlation between D₈₄ and bed gradient (S₀), while the sites with artificial dams (Noanet Woodlands and Harold Parker State Forest) showed an overall negative correlation. Further analyses include determining the effects of large-scale controls, such as land use, geology, and vegetation, versus local controls on sediment distribution.