Date of Graduation

Summer 2021

Degree

Master of Science in Geospatial Sciences

Department

Geography, Geology, and Planning

Committee Chair

Robert Pavlowsky

Keywords

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

Subject Categories

Forest Management | Hydrology | Water Resource Management

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.

Copyright

© Shoukat Ahmed

Open Access

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