Date of Award

2016

Document Type

Open Access Master's Report

Degree Name

Master of Science in Environmental Engineering (MS)

Administrative Home Department

Department of Civil and Environmental Engineering

Advisor 1

Dr. David W. Watkins

Committee Member 1

Dr. Martin T. Auer

Committee Member 2

Dr. Ann L. Maclean

Abstract

Before the advent of Light Detection and Ranging (LiDAR) technology, farm-level infrastructure for sustainable agriculture was designed using topographic maps. LiDAR is a remote sensing method whereby reflected laser pulses are measured to generate high-resolution 3D images of the terrain. This report compares these two methods in the design of grassed waterways for flood drainage and evaluates how the quantitative difference between the two methods can affect the overall hydrologic design. The benefits of LiDAR are expected to be higher accuracy and precision in design, as well as greater reproducibility or consistency, regardless of the designer. To carry out this analysis, design notes from 2001 to 2011 were acquired from the Perry Field Service Center of the Natural Resources Conservation Service (NRCS) of the US Department of Agriculture (USDA), and designs for thirty grassed waterways were randomly selected from Noble County, OK. ArcGIS was used to delineate the watersheds and compute the drainage areas and average watershed slopes for twenty-eight grassed waterways using LiDAR data. The NRCS Engineering Field Tool was then used to calculate the time of concentration, runoff depth, and peak discharge for the 10-year 24-hour storm, selected to match stated design criteria. These estimates were then compared to the original design notes, which were based on design methods using topographic maps. The results indicated a significant difference (p = 0.0001) in the mean watershed slopes, yielding lower times of concentration values and higher peak flow values with the LiDAR method. Smaller differences arise from the watershed delineation by LiDAR and the calculation of the runoff curve number (due to inclusion of more soil types). For a complete understanding of how methods based on LiDAR and topographic maps compare, this study should be done on a larger scale including different types of drainage structures. Until further study can be done, it is recommended that the topographic method be used in conjunction with the LiDAR method as a means for checking and adjusting for slope errors common to the LiDAR method.

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