Civil Engineering ETDs

Tomomi Ito

Publication Date

2-8-2011

Abstract

The objectives of this study were to estimate the influence of roots on the drainage facilities associated with the levees along the middle Rio Grande (MRG), and to suggest an appropriate drainage design. This study consists of three research elements: (1) GIS-based analysis in estimating root distribution along levees, (2) a bench-top experiment, and (3) evaluating a drainage designs using a numerical model. First, tree crown sizes were measured on GIS-based aerial photography to estimate root distributions. The results were compared with vegetation maps that were created based on field observations. The GIS-based measurements and field measurements showed similar values if the site was covered with a simple vegetation community. Simple canopy shapes improved the precision of the measurements. However, the GIS-based measurement was not accurate for a site with complex vegetation coverage. The bench-top experiment was conducted to evaluate the effectiveness of two types of geosynthetics as root barriers. A geotextile and a geocomposite were tested in v clear columns filled with soil and/or gravel to simulate six different drainage designs. Two New Mexican plants, Rio Grande cottonwood (Populus deltoides ssp. wislizeni) and coyote willow (Salix exigua), were selected, and planted in columns. The results showed roots of both species could penetrate through the geotextile and geocomposite. Also, root growth was not affected by the types of root barriers nor drainage material. For the last study element, HYDRUS-2D was applied to understand the soil water movement in the levee. The typical toe drain and the geocomposite edge drain were considered, and the models were run under the ambient condition (unsaturated) and the flood condition (saturated). As a result, the functions of both drainage designs were close to identical under the ambient condition since it did not result in drainage. In contrast, under the flood condition, the geocomposite edge drain could remove excess water more efficiently than the conventional toe drain.

Keywords

Riparian forest, Levee drainage, Root barrier, Geosynthetics, Drainage materials, Drain pipes, ArcGIS, HYDRUS-2D

Document Type

Thesis

Language

English

Degree Name

Civil Engineering

Level of Degree

Masters

Department Name

Civil Engineering

First Committee Member (Chair)

Coonrod, Julie

Second Committee Member

Cleverly, James

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