Date of Graduation

Summer 2021

Degree

Master of Science in Geospatial Sciences

Department

Geography, Geology, and Planning

Committee Chair

Robert Pavlowsky

Abstract

Despite their important role of headwater watersheds as a buffer for upland soil and vegetation disturbances, there has been little research about the effects of historical logging practices on present-day watershed hydrology and channel form. Middle Big Barren Creek (MBBC) watershed (48 km2 ) drains Mark Twain National Forest in the Ozark Highlands and was heavily logged from 1880 to 1920, reducing native shortleaf pine forest by 90%. Additionally, the frequency of intense rainfall events has increased in the region over the past 30 years. In this study, field surveys and hydrologic/hydraulic modeling were used to evaluate the historical timber harvesting impacts on hydrology and channel hydraulics along a 4.5 km segment of MBBC. The models were accurately calibrated with actual gage discharge data and water surface elevations yielding a Nash-Sutcliffe coefficient value of 0.85 and R2 = 1. Four different land use/cover scenarios were assessed to understand the history of hydrological alteration with five hydrologic parameters (flow duration, average discharge, runoff depth, peak discharge, and lag time ) and three hydraulic parameters (shear stress, stream power, and velocity). Pine forest cover tended to reduce runoff with the present-day peak discharge predicted to be 23% higher than with 100% pine cover, but 3% lower with 100% hardwood forest cover. Change from pine to hardwood forest composition caused reduced canopy interception (-29%) and higher peak flow (+60%) during a modeled early spring rainstorm. Compared to the pre-settlement condition, present-day shear stress (SS) increased among channel types for a bank-full flood as follows: (i) multi-threaded, 29%; (ii) single-channel, 59% and (iii) channelized/leveed 19%. Therefore, the single-channel form probably indicates a geomorphic response to higher runoff rates in these forest streams including coarser substrates. In the study segment, artificial over-widening of the channel resulted in bed aggradation.

Keywords

headwater streams, hydrologic and hydraulic modeling, shortleaf pine forest, historical logging effects, Ozark Highlands

Subject Categories

Forest Management | Hydrology | Water Resource Management

Copyright

© Shoukat Ahmed

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