MS Thesis Defense


Tiffany Sprague
Water Resources Science

May 7, 2019


They Paved Wetlands and Put Up a Road: Streams in Duluth, Minnesota (USA) seek free admission to tree museum for restoring altered flow regimes

Capitalizing on Duluth, Minnesota’s unique landscape comprised of sixteen high-value trout streams flowing through a mix of forest, wetland, urban and suburban environments, and available high-resolution GIS data, along with a current commitment to collaborative watershed management through the Duluth Urban Watershed Advisory Committee, this project aims to utilize high-resolution land cover maps, as well as field-surveys of flow from small stream reaches draining a variety of land use types, to demonstrate how the current landscape matrix drives small-scale stream hydrology, highlighting priority areas for cross-community preservation of forested headwaters. This study shows road density within Duluth-area subwatersheds is the largest land use contributor to altered flow regimes, decreasing lag time between precipitation and peak flow, increasing peak flow discharge, and decreasing baseflow stage. This study also demonstrates the need for additional best management practices such as larger stream buffer setbacks to slow overland flow and increase groundwater recharge, preservation of beaver dams to sustain year-round baseflow in small tributaries, and future design plans minimizing road density and stream-road crossings to maintain critical subsurface flow. As larger storm events plague northeastern MN, in combination with a growing population and expanding
urbanization, streams already show signs of altered hydrology, highlighting the importance for preservation of remaining natural vegetated areas in the headwaters, in combination with stormwater practices mimicking the infiltration capacity of these natural areas, so as to minimize further degradation of flow regimes and future impacts from flooding.