Soft engineering

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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. [1]

Contents

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. [2] 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. [3] 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. [1] 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. [3]

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. [4] 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. [5] 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. [2]

Principles of Soft Shoreline Engineering

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. [7]

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. [8]

Coir Logs

Erosion control coir logs are natural fiber products designed to stabilize soil by supporting erosion prone areas such as river banks, slopes, hills, and streams. Coir is coconut fiber extracted from the outer husk of a coconut and used in products such as ropes, mats, and nets. Like RECPs, coir logs are natural and biodegradable, being composed primarily of densely packed coir fibers held together by a tubular coir twine netting. Coir fiber is strong and water resistant, making it a durable barrier against waves and river currents. Multiple sections of coir log can be joined together by twine to provide erosion control and prevention to vulnerable areas. [9] Coir logs can also be vegetated and used to establish root systems of native plants along wetland edges.

Live Stakes and Fascines

Lives stakes and fascines are a specific tree or shrub species that thrive in moist soil conditions and can be strategically used to stabilize stream banks and shorelines. Live stakes are hardwood cuttings with the branches removed that, when planted in moist soil, will grow new plants from the stems of the cut branches. They can be used alone, implanted into 2-inch (5 cm) pilot holes in the soil, or used as a device to secure other bioengineering materials such as rolled erosion control products and coir logs. Fascines are similar live branches strapped together and laid horizontally across streambank contours to impede or prevent the flow of water and curb erosion. [10]

Brush Mattress

Brush mattresses, also known as live brush mats or brush matting is a technique used to form immediate protective cover of a streambank. Brush mattresses are dense compilations of live stakes, fascines, and branch cuttings held down with additional stakes to protect the embankment. The brush mattress is intended to eventually take root and enhance the conditions for the colonization of native plants. Along with aiding in the restoration of riparian habitats, this product intercepts sediment flowing downstream and provides a number of benefits for fish and aquatic species by offering physical protection from predators, regulating the water temperature, and shading the stream.

Live Cribwalls

Live crib walls are structures that resemble that of a wooden log cabin built into a streambank and rilled with natural materials such as soil, dormant wood cuttings, and rock. The live crib wall is able to fortify stream banks with the combination of the sturdy log structure and the root mass that will sprout from the wood cuttings and take hold deep in the bank, armoring it from erosion. Although quite labor intensive, cribwalls can last for decades and provide excellent aquatic habitats under the surface of the body of water. Cribwalls have the ability to prevent the occurrence of a split channel in a stream but should not be used in streams with downcutting as the base of the structure will be compromised. [11]

Encapsulated Soil Lifts

Encapsulated soil lifts are a technique that "encapsulates" soil in a biodegradable blanket and organized on a slope in such a way that creates the desired stream bank slope. The layers of soil, or lifts, are used to stabilize the banks of moderate to high level energy shorelines. Once constructed, the lifts are planted with the seeds of native flowers, shrubs and grasses. In addition to reducing dirt erosion in the body of water, soil lifts protect water quality and the encompassed riparian habitats. [12]

Vegetated Riprap

Vegetated riprap is a soft shoreline engineering technique that is an alternative to conventional riprap for erosion protection. Conventional riprap is a form of rock armor, rubble, or concrete used to fortify shoreline structures against the forces of erosion. Vegetated riprap is a more economically efficient form of shoreline protection that enhances fish and wildlife habitat as well as softening the appearance and improving embankment aesthetic. Vegetated riprap incorporated native vegetation along with rocks to create live cuttings in the bank. This technique improves the natural habitat of aquatic species along with armoring the banks and redirecting water flows. [13]

Geo Bags

Geo bags or erosion control bags/tubes act as sediment removing filters, protecting against shoreline erosion by trapping sludge and sand particles and preventing them from leaving the coastal area. The bags are designed to allow the natural flow of water to filter in and out without inhibition, limiting disruption to the coastline. These geo bags or tubes are designed to look natural in the coastal environment, as opposed to concrete alternatives, and are built to endure the outdoors. Geo bag material is typically composed of geotextile fabric and can be designed for different specifications. [14]

Best Management Practices

In order to incorporate principles of soft engineering into practice, shorelines must be redeveloped to achieve multiple objectives. For example, soft shoreline engineering has the ability to decrease costs, stabilize banks, enhance aesthetic value, protect riparian habitats, expand public access, and support a diversity of wildlife. [2] To achieve the goal of multiple objectives for waterfront development and design, a multi-disciplinary team must be formed to integrate environmental, social, and economic principles.

The first step in implementing soft engineering is conducting a preliminary assessment of the site and determining whether soft engineering is applicable and practical. A typical assessment includes identifying the extent of the project area, evaluating existing uses, documenting amenities and characteristics such as habitats, species, public access, development, and considering impact of future desired use. [2] If the team decides the site is fit to implement soft engineering, a complex process is designed in order to achieve the predetermined goals of the development and complete with objectives. Standards and targets must then be created to measure project development and progress. Interdisciplinary partnerships must be established at an early stage in the process to ensure the incorporation of environmental, social, and economic values, as well as target objectives implemented to measure progress. Priorities and alternative are established, with the team working together to decide on the best management practices to achieve maximum effectiveness. After best management practices have been determined and incorporated, project success is based upon the meeting of objectives and effective preservation and conservation efforts. [2]

Case Studies

Greater Detroit American Heritage River Initiative

In 1998, the President of the United States created the American Heritage River Initiative to restore and revitalize rivers and waterfronts through the use of newly introduced soft engineering techniques. [4] A report by Schneider reported that 47.2% of the U.S. and Canadian Detroit River had been fortified with concrete or steel, in accordance with traditional hard engineering management practices. In 1999, a U.S. Canadian SSE conference developed the best management practices for SSE use, which was put into effect among the 38 SSE projects that took place in the Detroit River-western Lake Erie watershed. A grand total of $17.3 million was spent on these projects which aimed to improve riparian and aquatic habitat, restore natural shoreline, and treat stormwater. The study found that the economic benefits to ecological restoration are profound and provide compelling evidence for further investigation and investment into shoreline rehabilitation processes. Researchers also found that SSE not only improved the natural habitat, but from a social perspective, the efforts aided in reconnecting people to nature, fostering a sense of human attachment to the success and health of these waterfronts. [1]

Mississippi

Beginning with British colonial establishment in 1819, Mississippi's coastline has undergone an extensive history of decline through alteration and land reclamation. Hilton and Manning found that from the period of 1922 to 1993, the area of mangroves, coral reefs, and intertidal mudflats decreased dramatically, the actual percentage of natural coastline dropping from 96 to 40%. [3] In order to combat these deleterious anthropogenic effects, Mississippi's government came up with a Master Plan in 2008 which incorporated the modification of shorelines in accordance with the ecological principles of soft engineering. A study regarding the success of ecological engineering in Singapore found that the most effective way to introduce ecological principles into shoreline design and preservation is to implement a top down approach that coordinates and educates the multitude of agencies that are involved in coastal management. Mississippi's loss of natural coastline is just one example of the inevitable detriment of intensive human development and soft engineering techniques provide an effective way to balance shoreline conservation and restoration with the urban development that is sure to continue. [3]


Related Research Articles

<span class="mw-page-title-main">Coastal erosion</span> Displacement of land along the coastline

Coastal erosion is the loss or displacement of land, or the long-term removal of sediment and rocks along the coastline due to the action of waves, currents, tides, wind-driven water, waterborne ice, or other impacts of storms. The landward retreat of the shoreline can be measured and described over a temporal scale of tides, seasons, and other short-term cyclic processes. Coastal erosion may be caused by hydraulic action, abrasion, impact and corrosion by wind and water, and other forces, natural or unnatural.

<span class="mw-page-title-main">Buffer zone</span> Intermediate region, typically between belligerent entities

A buffer zone is a neutral zonal area that lies between two or more bodies of land, usually pertaining to countries. Depending on the type of buffer zone, it may serve to separate regions or conjoin them. Common types of buffer zones are demilitarized zones, border zones and certain restrictive easement zones and green belts. Such zones may be comprised by a sovereign state, forming a buffer state.

<span class="mw-page-title-main">Bulkhead (barrier)</span> Anti-flooding structure

A bulkhead is a retaining wall, such as a bulkhead within a ship or a watershed retaining wall. It may also be used in mines to contain flooding.

<span class="mw-page-title-main">Seawall</span> Form of coastal defence

A seawall is a form of coastal defense constructed where the sea, and associated coastal processes, impact directly upon the landforms of the coast. The purpose of a seawall is to protect areas of human habitation, conservation and leisure activities from the action of tides, waves, or tsunamis. As a seawall is a static feature it will conflict with the dynamic nature of the coast and impede the exchange of sediment between land and sea.

<span class="mw-page-title-main">Revetment</span> Structures designed to absorb energy

A revetment in stream restoration, river engineering or coastal engineering is a facing of impact-resistant material applied to a bank or wall in order to absorb the energy of incoming water and protect it from erosion. River or coastal revetments are usually built to preserve the existing uses of the shoreline and to protect the slope.

<span class="mw-page-title-main">Geotextile</span> Textile material used in ground stabilization and construction

Geotextiles are permeable fabrics which, when used in association with soil, have the ability to separate, filter, reinforce, protect, or drain. Typically made from polypropylene or polyester, geotextile fabrics come in two basic forms: woven and nonwoven.

<span class="mw-page-title-main">Riprap</span> Rock or concrete protective armour

Riprap, also known as rip rap, rip-rap, shot rock, rock armour or rubble, is human-placed rock or other material used to protect shoreline structures against scour and water, wave, or ice erosion. Ripraps are used to armor shorelines, streambeds, bridge abutments, foundational infrastructure supports and other shoreline structures against erosion. Common rock types used include granite and modular concrete blocks. Rubble from building and paving demolition is sometimes used, as well as specifically designed structures called tetrapods.

<span class="mw-page-title-main">Coastal management</span> Preventing flooding and erosion of shorelines

Coastal management is defence against flooding and erosion, and techniques that stop erosion to claim lands. Protection against rising sea levels in the 21st century is crucial, as sea level rise accelerates due to climate change. Changes in sea level damage beaches and coastal systems are expected to rise at an increasing rate, causing coastal sediments to be disturbed by tidal energy.

<span class="mw-page-title-main">Riparian zone</span> Interface between land and a river or stream

A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks are called riparian vegetation, characterized by hydrophilic plants. Riparian zones are important in ecology, environmental resource management, and civil engineering because of their role in soil conservation, their habitat biodiversity, and the influence they have on fauna and aquatic ecosystems, including grasslands, woodlands, wetlands, and even non-vegetative areas. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone,riparian corridor, and riparian strip are used to characterize a riparian zone. The word riparian is derived from Latin ripa, meaning "river bank".

<span class="mw-page-title-main">Erosion control</span> Practice of preventing soil erosion in agriculture and land development

Erosion control is the practice of preventing or controlling wind or water erosion in agriculture, land development, coastal areas, river banks and construction. Effective erosion controls handle surface runoff and are important techniques in preventing water pollution, soil loss, wildlife habitat loss and human property loss.

Hard engineering involves the construction of hydraulic structures to protect coasts from erosion. Such structures include seawalls, gabions, breakwaters, groynes and tetrapods.

Beach evolution occurs at the shoreline where sea, lake or river water is eroding the land. Beaches exist where sand accumulated from centuries-old, recurrent processes that erode rocky and sedimentary material into sand deposits. River deltas deposit silt from upriver, accreting at the river's outlet to extend lake or ocean shorelines. Catastrophic events such as tsunamis, hurricanes, and storm surges accelerate beach erosion.

<span class="mw-page-title-main">Sand dune stabilization</span> Coastal management practice

Sand dune stabilization is a coastal management practice designed to prevent erosion of sand dunes. Sand dunes are common features of shoreline and desert environments. Dunes provide habitat for highly specialized plants and animals, including rare and endangered species. They can protect beaches from erosion and recruit sand to eroded beaches. Dunes are threatened by human activity, both intentional and unintentional. Countries such as the United States, Australia, Canada, New Zealand, the United Kingdom, and Netherlands, operate significant dune protection programs.

<span class="mw-page-title-main">Buffer strip</span>

A buffer strip is an area of land maintained in permanent vegetation that helps to control air quality, soil quality, and water quality, along with other environmental problems, dealing primarily on land that is used in agriculture. Buffer strips trap sediment, and enhance filtration of nutrients and pesticides by slowing down surface runoff that could enter the local surface waters. The root systems of the planted vegetation in these buffers hold soil particles together which alleviate the soil of wind erosion and stabilize stream banks providing protection against substantial erosion and landslides. Farmers can also use buffer strips to square up existing crop fields to provide safety for equipment while also farming more efficiently.

<span class="mw-page-title-main">Riparian buffer</span> Vegetated area near a stream, usually forested

A riparian buffer or stream buffer is a vegetated area near a stream, usually forested, which helps shade and partially protect the stream from the impact of adjacent land uses. It plays a key role in increasing water quality in associated streams, rivers, and lakes, thus providing environmental benefits. With the decline of many aquatic ecosystems due to agriculture, riparian buffers have become a very common conservation practice aimed at increasing water quality and reducing pollution.

<span class="mw-page-title-main">Stream restoration</span>

Stream restoration or river restoration, also sometimes referred to as river reclamation, is work conducted to improve the environmental health of a river or stream, in support of biodiversity, recreation, flood management and/or landscape development.

<span class="mw-page-title-main">Coastal engineering</span> Branch of civil engineering

Coastal engineering is a branch of civil engineering concerned with the specific demands posed by constructing at or near the coast, as well as the development of the coast itself.

<span class="mw-page-title-main">Alluvial river</span> Type of river

An alluvial river is one in which the bed and banks are made up of mobile sediment and/or soil. Alluvial rivers are self-formed, meaning that their channels are shaped by the magnitude and frequency of the floods that they experience, and the ability of these floods to erode, deposit, and transport sediment. For this reason, alluvial rivers can assume a number of forms based on the properties of their banks; the flows they experience; the local riparian ecology; and the amount, size, and type of sediment that they carry.

<span class="mw-page-title-main">Riparian-zone restoration</span> Ecological restoration of river banks and floodplains

Riparian-zone restoration is the ecological restoration of riparian-zonehabitats of streams, rivers, springs, lakes, floodplains, and other hydrologic ecologies. A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the fifteen terrestrial biomes of the earth; the habitats of plant and animal communities along the margins and river banks are called riparian vegetation, characterized by aquatic plants and animals that favor them. Riparian zones are significant in ecology, environmental management, and civil engineering because of their role in soil conservation, their habitat biodiversity, and the influence they have on fauna and aquatic ecosystems, including grassland, woodland, wetland or sub-surface features such as water tables. In some regions the terms riparian woodland, riparian forest, riparian buffer zone, or riparian strip are used to characterize a riparian zone.

<span class="mw-page-title-main">Living shorelines</span>

Living shorelines are a relatively new approach for addressing shoreline erosion and protecting marsh areas. Unlike traditional structures such as bulkheads or seawalls that worsen erosion, living shorelines incorporate as many natural elements as possible which create more effective buffers in absorbing wave energy and protecting against shoreline erosion. The process of creating a living shoreline is referred to as soft engineering, which utilizes techniques that incorporate ecological principles in shoreline stabilization. The natural materials used in the construction of living shorelines create and maintain valuable habitats. Structural and organic materials commonly used in the construction of living shorelines include sand, wetland plants, sand fill, oyster reefs, submerged aquatic vegetation, stones and coir fiber logs.

References

  1. 1 2 3 Hartig, J.H.; Zarull, M.A.; Cook, A. (2011). "Soft shoreline engineering survey of ecological effectiveness". Ecological Engineering. 37 (8): 1231–1238. doi:10.1016/j.ecoleng.2011.02.006.
  2. 1 2 3 4 5 6 Caulk, A.D., Gannon, J.E., Shaw, J.R., Hartig, J.H. "Best management practices for soft engineering of shorelines." Greater Detroit American Heritage River Initiative, Detroit, Michigan, USA. 2000.
  3. 1 2 3 4 Lai, Samantha; Loke, Lynette H.L.; Hilton, Michael J.; Bouma, Tjeerd J.; Todd, Peter A. (2015). "The effects of urbanisation on coastal habitats and the potential for ecological engineering: A Singapore case study". Ocean & Coastal Management. 103: 78–85. doi:10.1016/j.ocecoaman.2014.11.006.
  4. 1 2 Hartig, John H.; Kerr, John K.; Breederland, Mark (2001). "Promoting soft engineering along Detroit River shorelines". Land and Water-The Magazine of Natural Resource Management and Restoration. Fort Dudge, Iowa. 45 (6): 24–27.
  5. ↑ United States Army Corps of Engineers (August 1, 2008). "The Coastal Engineering Manual". EM 1110-2-1100.{{cite journal}}: Cite journal requires |journal= (help)
  6. 1 2 "Principles and Objectives of Soft Shoreline Stabilization | Coastal Processes, Hazards, and Society". www.e-education.psu.edu. Retrieved 2019-02-28.
  7. 1 2 "Shoreline Stabilization Techniques - NYS Dept. of Environmental Conservation". www.dec.ny.gov. Retrieved 2019-02-28.
  8. ↑ Urban Drainage and Flood Control District (November 2010). "Urban Storm Drainage Criteria Manual". 3.{{cite journal}}: Cite journal requires |journal= (help)
  9. ↑ "Coir Logs | Natural Erosion Control for Soil Stabilization". www.erosioncontrol-products.com. Retrieved 2019-02-28.
  10. ↑ "Live Stakes & Fascines - Cardno Native Plant Nursery". www.cardnonativeplantnursery.com. Retrieved 2019-02-28.
  11. ↑ Ohio Department of Natural Resources. "Live Cribwalls" (PDF). Ohio Stream Management Guide. Guide No. 17: 57–59.
  12. ↑ "Encapsulated soil lifts are lake-friendly option for rebuilding eroding banks on inland lakes". MSU Extension. Retrieved 2019-02-28.
  13. ↑ "Vegetated Riprap, Vegetated Riprap Applications ~ Innovative Techniques". www.terraerosion.com. Retrieved 2019-02-28.
  14. ↑ "Erosion Control Bags for Coastal Protection". www.erosioncontrol-products.com. Retrieved 2019-02-28.

See also

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