Doctoral Dissertations

Date of Award

5-2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Civil Engineering

Major Professor

John S. Schwartz

Committee Members

Daniel C. Yoder, Eric C. Drumm, Russell Zaretzki, Glenn Tootle

Abstract

The use of loose spoil on steep slopes for surface coal mining reclamation sites has been promoted by the US Department of Interior, Office of Surface Mining for the establishment of native forest. Although low-compaction spoils improve tree survival and growth, the erodibility and hydrology of steep slopes may change due to this practice. The purpose of this study was to quantify the erodibility (K factor), and the Curve Number (CN) value for low compaction, steep-sloped (> 20%) reclaimed mine lands in the Appalachian region, USA. This study also investigated the performance of the SEDCAD model in estimating erosion and sediment delivery from these slopes, and tried to estimate the potential change in rainfall erosivity due to climate change in the study region.

Three active coal mining sites in the Appalachian region of East Tennessee were monitored for rainfall, runoff, and sediment yields. The estimated time-varying K factor ranged between 0.03 and 0.5 t۰ha۰h۰ha-1۰MJ-1۰mm-1, with the highest values immediately following reclamation site construction. Rill development greatly influenced sediment yields. A fining of delivered sediment size was observed from the period of rill development to relatively stable rill morphology, with the D84 changed from 17.3 mm to 1.7 mm. Meanwhile, different methods were used to identify CN values of these new reclaimed surfaces as they are vital for design of runoff and sediment control structures. In contrast to previous studies, CN estimation methods utilized in this study propose a narrower, more practical CN value range of 58.5 ~ 60.0, based on standard asymptotic behavior, for low-compaction steep-sloped reclaimed surfaces.

This study also investigated the performance of SEDCAD in estimating erosion and sediment delivery. Model input parameters were assessed with respect their impacts on SEDCAD outputs. In general, SEDCAD appeared to overestimate sediment yield compared to what was measured from study sites, and modeled sediment yields were found to be sensitive to CN selection. Finally, this study showed that for all future greenhouse gas emission scenarios the overall annual rainfall erosivity will increase in the study area, though the distribution of erosivity throughout the year will be similar to the present.

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