Regarding the civil engineering of shorelines, soft engineering is a shoreline management practice that uses sustainable ecological principles to restore shoreline stabilization and protect riparian habitats. Soft Shoreline Engineering (SSE) uses the strategic placement of organic materials such as vegetation, stones, sand, debris, and other structural materials to reduce erosion, enhance shoreline aesthetic, soften the land-water interface, and lower costs of ecological restoration. To differentiate Soft Shoreline Engineering from Hard Shoreline Engineering, Hard Shoreline Engineering tends to use steel sheet piling or concrete breakwalls to prevent danger and fortify shorelines. Generally, Hard Shoreline Engineering is used for navigational or industrial purposes. To contrast, Soft Shoreline Engineering emphasizes the application of ecological principles rather than compromising the engineered integrity of the shoreline. The opposite alternative is hard engineering.
Background Hard shoreline engineering is the use of non-organic reinforcing materials, such as concrete, steel, and plastic to fortify shorelines, stop erosion, and protect urban development from flooding. However, as shoreline development among coastal cities increased dramatically, the detrimental ecological factors became apparent. Hard shoreline engineering was designed to accommodate human development along the coast, focusing on increasing efficiency in the commercial, navigational, and industrial sectors of the economy. In 2003, the global population living within 120 miles (190 km) of an ocean was 3 billion and is expected to double by the year 2025. These developments came at a high cost, destroying biological communities, isolating riparian habitats, altering the natural transport of sediment by disrupting wave action and long-shore currents. Many coastal regions began to see significant coastal degradation due to human development, the Detroit River losing as great as 97% of its coastal wetland habitats. Singapore, as well, documented the disappearance of the majority of its mangrove forests, coastal reefs, and mudflat regions between 1920 and 1990 due to shoreline development. Towards the end of the 20th century, coastal engineering practices underwent a gradual transition towards incorporating the natural environment into planning considerations. In stark contrast to hard engineering, employed with the sole purpose of improving navigation, industrial and commercial uses of the river, soft engineering takes a multi-faceted approach, developing shorelines for a multitude of benefits and incorporating consideration of fish and wildlife habitat. Tasked with the responsibility to construct and maintain United States Federally authorized coastal civil works projects, the U.S. Army Corps of Engineers plays a major part in the development of the principles of coastal engineering as practiced within the U.S. In part due to degradation of coastline across the United States, the Corps has since updated its coastal management practices with an increased emphasis on computer-based modeling, project upkeep, and environmental restoration. However, soft and hard engineering are not mutually exclusive; a blend of the two management practices can be used to design waterfronts, especially for high flow bodies of water.
Principles of Soft Shoreline Engineering Imitate Nature - Imitating the characteristics of the natural environment is critical to the success of soft engineering efforts. Existing traits of a landscape provide telltale signs of the geomorphic forces at play. Trying to add vegetation to a barren area with high winds will not produce the intended results. Gentle Slopes - Gentle slopes are most commonly found in the natural environment and are the most stable under the forces of gravity. Gradually inclined slopes along banks and shorelines allow for the dissipation of wave energy over a greater distance, reducing the force of erosion. "Soft Armoring" - Soft armoring includes the use of materials such as live plants, shrubs, root wads, logs, vegetative mats, etc. These materials, which are alive, can adapt to changes in the environment and help maintain regular coastal processes by disrupting the natural shoreline in the least way possible. Soft armoring is also paramount to enhancing shoreline habitats and improving water quality. Material Variety - A variety of textures and vegetation enhances aesthetic, diversifies the natural landscape, and maximizes biodiversity. Native plants and endangered or threatened species should be used whenever possible. The use of locally abundant and easily accessible natural resources also cuts development costs significantly.
Techniques
Planting The most basic and fundamental form of soft shoreline engineering is adding native vegetation to degraded or damaged shoreline areas to bolster the structural integrity of the soil. The deep roots of the vegetation bind the soil together, strengthening the structural integrity of the soil and preventing it from cracking apart and crumbling into the body of water. An added layer of vegetation also protects embankments from corrosive forces such as rain and wind.
Rolled Erosion Control Products (RECP) Rolled erosion control products are blankets or netting created with both natural and synthetic materials used to protect the surface of the ground from erosive forces and promote the growth of vegetation. RECPs are often used in locations highly susceptible to erosion, such as steep slopes, channels, and areas where natural vegetation is sparse. These products aid the growth of vegetation by protecting soil from raindrops, keeping seed in place, and maintaining moisture and temperature parameters consistent with plant growth. The typical composition of an RECP includes seed, fertilizer, degradable stakes, and a binding material. Although design varies by manufacturer, most RECPs are biodegradable or photodegradable and decompose after a given amount of time.
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