Scoping Study for the Development of Design Guidelines for Bioengineering in the Upper Midwest

Abstract

It has been about fifteen years since soil bioengineering and bioengineering technology have been used in projects to protect slopes and river banks against erosion in the U. S. Now many consulting firms as well as state and federal agencies promote and practice these techniques. Despite a widespread support of these techniques, many projects have failed. Therefore, it is deemed necessary to develop a set of design guidelines to ensure a higher rate of success. In order to develop design guidelines for soil bioengineering and bioengineering technology, a pilot study was conducted to determine the amount of work already done in these areas, and to define the existing research needs. This report comprises (a) a summary of literature review, (b) interviews with eleven practitioners in the field, (c) an evaluation of three projects done in Minnesota, (d) current research needs, (e) and a brief evaluation of three sites in the vicinity of the Twin Cities area as potential outdoor laboratories to conduct research in the needed areas. It also includes a summary of a site visit of the Department of Soil Bioengineering and Landscape Construction at the University of Agricultural Sciences in Vienna, Austria. The study shows that a significant number of studies have been done on topics related to soil bioengineering techniques. However, these studies mainly address the problems at a micro scale, and hence, there is a gap between existing knowledge and practice. Therefore, there is an urgent need to not only study some of the fundamental processes and mechanisms involved in soil bioengineering techniques, but also to investigate these processes at a macro scale to evaluate their strengths and impacts when applied to streambanks and slopes. Main highlights of the research needs identified in this study were a) quantifying the bank and bed roughness with the most common plants used in bioengineering techniques, b) studying the added shear strength to banks by vegetation, c) determining the resiliency of different plants under high flow conditions, e) understanding the mechanisms which cause failure of plants under different flow conditions, f) quantifying the shear strength of the commonly used techniques for a range of bank slopes, top soil depths and soil types, and g) determining the shear strength of composite systems, where different plants and techniques are combined. To conduct research in the needed areas three sites were identified and evaluated as potential outdoor research facilities in the vicinity of the Twin Cities area, Minnesota. The three candidate sites were (1) the two abandoned wasteways near the Falls of St. Anthony located adjacent to the St. Anthony Falls Laboratory, (2) a 7 acre area in the northern part of the UMore Park, a University of Minnesota property allocated for research, and (3) a short reach of the Vermillion River near Empire, MN, located on private property.