Figure 1. General Motors Corporation's Wintergarden at the Renaissance Center facing the Detroit River (rendering courtesy of Hines Development and Skidmore Owings & Merrill, LLP Master Architects).

Hard vs. Soft Engineering of Shorelines

On November 23, 1999, the Greater Detroit American Heritage River Initiative held its first major stakeholder event to look at options on how to reshape the Detroit River shoreline using techniques of soft engineering. Hard engineering of shorelines is generally defined as the use of concrete breakwalls or steel sheet piling to stabilize shorelines and achieve safety. There are many places along our working river where hard engineering is required for navigational or industrial purposes. Much of the Detroit River shoreline is already hardened. However, there is growing interest in using soft engineering of shorelines in appropriate locations. Soft engineering is the use of ecological principles and practices to reduce erosion and achieve the stabilization and safety of shorelines, while enhancing habitat, improving aesthetics, and saving money. Soft engineering is achieved by using vegetation and other materials to soften the land-water interface, thereby improving ecological features without compromising the engineered integrity of the shoreline.

Rationale for Soft Engineering

Hard engineering typically has no habitat value for fish or wildlife. Soft engineering incorporates habitat for fish and wildlife. The Detroit River is one of the most biologically diverse areas in the Great Lakes Basin. In 1998, the U.S.-Canada State of the Lakes Ecosystem Conference (SOLEC) identified the Detroit River-Lake St. Clair ecosystem as one of 20 Biodiversity Investment Areas in the entire Great Lakes Basin Ecosystem with exceptional diversity of plants, fish, and birds, and the requisite habitats to support them (Reid et al. 1999). The State of the Lakes Ecosystem Conference went on to call for special efforts to protect these unique ecological features. Many people who appreciate the outdoors know that the Detroit River supports a nationally renowned sport fishery. For example, the City of Trenton, located on the Trenton Channel at the lower end of the Detroit River, hosted a major walleye fishing tournament called "Walleye Week" in 1999. "Walleye Week" attracted people from all over North America to compete in the In-Fisherman Professional Walleye Tournament, the Team Walleye Tournament, and the Michigan Walleye Tournament offering $240,000 in prize money. It is estimated that walleye fishing alone brings in $1,000,000 to the economy of communities along the lower Detroit River each spring.

Another reason why soft engineering practices should be encouraged is because it is well recognized that there is limited public access to the Detroit River, particularly on the United States side. Use of multiple-objective soft engineering of shorelines will increase public access to the river.

There are also economic benefits associated with use of soft engineering. In general, soft engineering of shorelines is typically less expensive than hard engineering of shorelines. Additionally, long-term maintenance costs of soft engineering are generally lower because soft engineering uses living structures, which tend to mature and stabilize with time.

Technology Transfer

Over 200 people attended the November 23rd conference to:

• learn from case studies of soft engineering of shorelines from places like Toronto, Hamilton Harbour, and Thunder Bay, Ontario, the Upper Mississippi River in Minnesota, and the Kenai River in Alaska;
• hear about recent work on cost-benefit analysis of soft vs. hard engineering of shorelines; and
• discuss where and how soft engineering might be used along the Detroit River (see Appendix A for the program and Appendix B for a list of participants).

The soft engineering case studies presented at the conference and additional ones contributed for this best management practices manual are listed in Table 1.

Participants in the November 23rd soft engineering conference learned that it is important to redevelop and redesign our shorelines for multiple objectives. Shorelines can be stabilized and achieve safety, while increasing public access, enhancing habitat, improving aesthetics, and saving money. Hard engineering of shorelines, in the form of steel sheet piling, can cost as much as $1,000 per linear foot. We cannot afford to use hard engineering along the entire length of the Detroit River shoreline, nor do we want fully hard engineered shorelines because they have no habitat value and will not support the diversity of fish and wildlife found in our river. Participants also learned that hard and soft engineering are not mutually exclusive, there are places where attributes of hard and soft engineering can be used together. This makes sense in a high-flow river like the Detroit River through which the entire upper Great Lakes pass.

It is critically important that the right people get involved upfront in redevelopment projects to be able to incorporate principles of soft engineering into future waterfront designs. The design process must identify opportunities and establish partnerships early in the process which achieve integrated ecological, economic, and societal objectives.

Table 1. A list of soft engineering case studies presented.

Integrated Approach to Design, Implementation, and Evaluation of Effectiveness

Figure 2 presents one potential design and implementation framework which encourages incorporating soft engineering practices into shoreline developments. As noted above, it is critically important that the right people get involved upfront in shoreline redevelopment projects to be able to incorporate principles of soft engineering into future waterfront designs. However, project leaders must first perform a preliminary assessment which:

• defines the geographic extent of the project or study area;
• inventories existing shoreline uses (habitat, public access, etc.); and
• evaluates existing uses against historical conditions and desired future uses.

Figure 2. A framework to help incorporate soft engineering practices into shoreline developments.