Analyzing the Development of Beaver Ponds at Seasonal and Annual Scales via UAV and Satellite Remote-Sensing;

Abstract:

Beaver are prevalent throughout North America and their associated impoundments impact catchment hydrology in multiple ways, from dampening peak flows to a hypothesized increase in summer baseflows. However, little is known about the variability of the spatial and temporal distribution of these impoundments, what metrics determine presence or absence of ponds, and how pond presence might affect the hydrology in semi-arid, snow dominated landscapes. To address these questions, we conducted a multi-tiered research campaign in the Laramie Range of Southeastern Wyoming. While beavers are usually trapped on private land, portions in the Laramie Range are public land, which allowed for beavers to thrive and establish dams. In a first step, we used National Agricultural Imagery Program (NAIP) data and random forest image classification schemes to investigate climatic and physiographic controls on beaver pond locations and sizes. There was little variability in pond numbers, pond extents and sizes in first and second order streams over the 16 years of NAIP coverages. Moreover, climate metrics such as precipitation and snow melt magnitudes seem to have a limited impact on changes in pond areas. In contrast, pond distribution appears to be controlled primarily by topographic characteristics such as upslope accumulated area (UAA) and watershed slope. To understand the interannual dynamics of impounded water and their associated headwater systems, we use a two-prong approach. First, 25 Temperature sensors were installed in first-order streams to estimate streamflow persistence over a range of beaver activity. Differences in temperature amplitudes reveal when streams dry up as the summer progresses. A UAV-mounted multispectral camera was used to delineate the seasonal extents of two pond complexes throughout the summer baseflow period. This work increases our understanding of controls on beaver pond locations in small headwater catchments and how impoundments influence the hydrologic regimes of semi-arid, snow dominated watersheds.