Date on Master's Thesis/Doctoral Dissertation

5-2020

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Civil and Environmental Engineering

Degree Program

Civil Engineering, PhD

Committee Chair

Parola, Arthur

Committee Member

Rockaway,Thomas

Committee Member

Gerber, Erin

Committee Member

Bhaskar, Nageshwar

Author's Keywords

Stream restoration; two dimensional hydrodynimc model; erosion; velocity; shear stress

Abstract

In the design of stream restorations, boundary shear stress (shear stress) and velocity during high flow events are the key parameters in the assessment of the risk of morphological failure associated with channel bank and bed erosion and sediment transport. The use of two-dimensional hydrodynamic models (2D Models) is becoming more common to estimate critical shear stress and velocity for stream restoration projects. These models can give detailed distribution of shear stress and velocity over floodplain surfaces and channel. Obtaining reliable and correct estimates of stress and velocity require an accurate digital terrain model, estimates of input flows at the upstream, approximation of water surface elevation at the downstream, and surface roughness coefficients. Obstacles to the use of these models include the cost associated with extensively detailed terrain surveys, distributed information about the roughness coefficients, and the determination of appropriate flow conditions that must be modeled to identify erosion susceptible components. In the present research, the reliability of the use of 2D models for predicting regions of streambanks and floodplain that are susceptible to erosion is assessed. For this purpose, two-dimensional hydrodynamic modeling software (TUFLOW) is employed to evaluate the accuracy of the model for assessing the risk of having erosion by comparing with field observation. Also, the results of this study have been compared with the existing recommendations for the risk of having erosion. Topography and hydraulic data obtained from monitoring efforts of the restored channel and floodplain of Slabcamp Creek located in Rowan County, Kentucky was used to develop and calibrate the 2D Model. Also, the topographic data from the restored floodplain and channel of Brushy Creek located in Greenup County, Kentucky was used for doing the simulation as the second study site. Areas of bank and floodplain erosion were developed approximately from aerial surveys. The relations between the model hydraulic parameters and areas of observed erosion were developed based on model results and the aerial surveys. In both the Slabcamp and Brushy analysis for the bank and floodplain areas, shear stress over 4 psf and velocity over 6 fps showed high percentage area of erosion.

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