Water-caused erosion prevention

A riparian zone in New Zealand. Photo: Dairy News

Recent modern solutions to managing the effects of water-caused erosion have tended toward ‘hard’ infrastructure solutions such as sea walls. Unfortunately, these methods are increasingly unsuccessful as long-term solutions. Nature-based solutions can be implemented instead, or in addition to existing protections, to prevent erosion caused by water, using natural processes and green or hybrid infrastructure. Various solutions have emerged as prevention measures for erosion caused by water. The primary ones that relate to nature-based solutions are vegetation barriers and hybrid barriers.

Vegetation barriers: Vegetation is one of nature’s simplest and most effective ways to manage water and erosion. Planting can act as a vegetation barrier, to prevent or reduce erosion of gullies and banks, to reduce risk of landslides, and to prevent or reduce sedimentation entering streams (Gavin, 2023). 

Gavin (2023) suggests nature-based planting solutions to preventing erosion along waterways:

  • Afforestation: dense planting of a mixture of trees creates root systems that hold soil tight into slopes, stabilising gullies.
  • Spaced planting: planting trees at maximum 10m spacing can reduce the change of landslides by up to 95%.
  • Buffer planting: closely planted native grasses can capture silt and sediment, and reduce runoff velocity. 
  • Riparian planting: holding riverbanks together with deeply rooted trees to improve soil stability and enhance filtration. 

In coastal settings, vegetation barriers formed of dune vegetation, biogenic reefs, mangroves, marshes, and dense planting are able to protect coastal areas from erosion and flooding by dissipating the hydrodynamic energy through their submerged canopies or structural complexity (Juanes et al., 2022). 

Hybrid barriers: Solutions to erosion caused by water can also be a hybrid, or mixture of hard and soft solutions. In coastal environments, Knight (2023) shows that natural landforms of different environments can serve the same function as hard-engineered methods. Beaches, dunes, islands, marshes and mangroves, coral and oyster reefs, either alone or in combination with traditional hard infrastructure can reduce damage to shorelines (NCCOS, 2023). 

Research into the prevention of erosion caused by water has introduced various interesting hybrid methods:

  • Baek et al. (2020) introduce a hybrid method for erosion control that combines the submerged breakwater with an artificial coral reef.
  • Hur et al. (2019) experimented with controlling the water flow of an open inlet by developing a submerged breakwater with a drainage channel to reduce the water-level rise behind the structure.
  • Oh et al. (2006) employed a geotextile tube technology to create shore protection structures

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Name of NbS

Water-caused erosion prevention

Type of NbS

Hybrid living/engineered interventions

Location

Urban, Periurban and Rural: anywhere where erosion is caused by water.

Planting methods can add resilience to erosion. Photo: Boffa Miskell

Relationship to Indigenous knowledge

Increased erosion caused by climate change poses an enormous threat to coastal communities in Te Moananui Oceania. Indigenous people in the region rely heavily on, and have a deep cultural connection to the shoreline and the ocean. Indigenous communities in the Pacific are resilient and have been adapting to the changes of the ocean and the shoreline for milenia. The use of nature-based solutions to prevent erosion is a way of protecting traditional geographic habitats or ancestral territories in a way that allows them to preserve a reciprocal relationship with their community, their land, rivers, and the sea.

Climate change benefits
  • Changes in rainfall
  • Coastal erosion
  • Coastal inundation and storm surge
  • Flooding
  • glacial retreat and snow cover change
  • Reduced soil quality
  • Sea level rise
  • Soil erosion and landslides
  • Wind / storm damage

Erosion is the process in which earthen materials are worn away by natural forces like wind and water. The process creates sediment; eroded soil particles. As the climate changes, there are more intense rain events, sea level rise, and increased storm events, all of which lead to flooding, coastal inundation, landslides and reduced soil quality. The changes in water patterns, higher water levels and faster velocities in waterways increase erosion and result in more sediment in rivers, lakes, streams, and reefs (EPA, 2023). An increase in sediment disrupts water quality and disturbs habitats and ecosystems.

Soil erosion is increasingly problematic in both fresh and ocean waters; it threatens coastal areas, as well as areas near rivers, lakes and streams, and hills and gullies (MPI, 2014). Globally, almost 1 billion people now live within 10km of a coastline, and the same number live in areas less than 10 metres above sea level (Knight, 2023). A survey in 2018 showed that 24% of sandy coasts globally were already experiencing persistent net erosion because of climate change (Aarninkhod et al., 2018).

The use of vegetation barriers, or carefully considered hybrid methods, as nature-based solutions to water-caused erosion can build resilience to climate change. See also: Living Crib Walls.

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Societal / socio-cultural benefits
  • Disaster risk reduction and resilience
  • Food security

Across the Pacific, coastal erosion is exacerbated by natural disasters, changes in rainfall, sea level rise and flooding. Coastal infrastructure and food sources are damaged, and land loss leads to displacement and uncertainty. 

The ability to create solutions to erosion that communities can understand, construct or plant, and maintain is essential to their success. Barriers of vegetation along coastlines and waterways are a solution that is both effective and kind to the natural environment, and requires no external aid, as it can be maintained by the community who live in the area. This gives the community autonomy and the ability to create and maintain their own resilience to natural disasters. 

Soil is vital to food growing and therefore food security. 

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Ecological and biodiversity benefits
  • Disturbance prevention (erosion, storm damage, flooding etc.)

ecologically beneficial than hard infrastructure. The vegetation barriers will grow naturally over time, creating areas of recreation and adding natural appeal to landscapes. Additionally, vegetated areas create opportunities to restore habitats of birds, insects, and fish, which is especially beneficial where habitats have been damaged by erosion.

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Planting of a vegetated buffer zone to manage water-caused erosion. Image: Great Rivers Greenway

Technical requirements

The technical requirements of water-caused erosion methods vary significantly based on their application, size and intended purpose. 

A vegetated barrier can be as simple as planting solutions along a streambank, or as complicated as entirely new planted and constructed landscapes along coastlines. Selecting the right species and creating nurseries to supply plants for larger schemes is likely to be key.

Issues and Barriers

Solutions to water-caused erosion must consider the natural, dynamic nature of water; coastlines and waterways are naturally constantly dynamic and moving. They cannot be easily controlled by one simple solution.

In order to create successful solutions, there should be consideration of where the bodies of water are flowing from, and to. Each stream, river, or ocean is influenced by unique climactic, cultural and ecosystem conditions. And more often than not, bodies of water are connected and influenced by each other.

In Te Moananui Oceania, where foreign aid continues to flow, often a Western lens is applied to solutions to climate change (Mihaere et al., 2024). Solutions to water-caused erosion prevention must consider the socio-cultural implications of applied infrastructure on communities. 

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Opportunities

As foreign aid continues to flow into Oceanic nations, to aid in climate change resilience, there should be consideration of nature-based alternatives to hard infrastructure solutions. There is an opportunity to work with local communities to create vegetated barriers that they can create and maintain themselves; solutions that work with nature in the same way the people of the Pacific have been doing for millennia.

Financial case

Vegetated barriers can be implemented on small and large scales, so their cost can be flexible and adjustable. The cost of maintaining them can be minimal if a local community is involved. 

References

Further resources: