NbS-06

Sediment Capture Traps

Sediment capture traps are designed to capture and retain sediments that would otherwise be carried downstream by river currents. These traps play a crucial role in controlling sediment transport, reducing erosion, and improving water quality by preventing excessive sedimentation in downstream habitats.

They can be engineered elements such as sediment basins, weirs, or dams, or natural features like gravel bars or vegetated floodplains. These modifications slow down water flow, allowing sediments to settle and helping to retain valuable nutrients and organic matter that might otherwise be lost.

This retention improves soil fertility, supports the growth of aquatic vegetation, and enhances overall ecosystem health. By reducing suspended solids in the water, sediment capture traps help improve water clarity and quality, preventing pollution and habitat degradation. This is especially important in river systems near urban, industrial or agricultural areas, where excessive sedimentation can contribute to water quality issues and harm aquatic habitats.































LANDSCAPES SUPPORTED








    
        Flood responsive Riverine and Deltaic Landscapes
    




    
        Flood-responsive Dry River Landscapes
    




    
        Regenerative Agriculture
    










EbA (ECOSYSTEM-BASED APPROACHES)






  • Ecosystem based adaptation
  • Green infrastructure
  • Ecosystem restoration
  • Sustainable land management






MAIN PROBLEMS ADDRESSED







                    Soil Erosion
                    Soil Erosion
                

                    Biodiversity Loss
                    Biodiversity Loss
                

                    Flood Control
                    Flood Control
                

                    Carbon Sequestration
                    Carbon Sequestration
                









EbA (ECOSYSTEM-BASED APPROACHES)








        

            
SUPPORTING
    

  • Trapping systems help retain nutrients that would otherwise be lost, promoting nutrient cycling and improving soil fertility in agricultural or forested areas.
    • 

  • Protect aquatic and terrestrial habitats by reducing the smothering of critical habitats.
    • 

REGULATING
    

  • Stabilize the soil in areas prone to erosion by capturing sediments before they can be carried downstream.Helps maintain the capacity of river channels, preventing flooding.
    • 

  • Prevent pollutants that may be carried with the sediment from reaching water bodies.
    • 


            
PROVISIONING
    

  • Contribute to agricultural productivity by reducing soil erosion and preserving fertile soils.
    • 

  • In forest areas, prevents soil erosion, which in turn maintains forest health and contributes to the availability of timber and other forest resources.
    • 

SOCIAL BENEFITS
    

  • Preserving these landscapes (wetlands, rivers, floodplains) through sediment management contributes to cultural heritage.
    • 


        















NbS6_Permanent Sedimentation Basin
NbS6_Sediment Capture Trap_Queensland with Legends









PROJECT’S CHALLENGES & RISKS






        

            
Extreme Weather Events: Sediment traps can be overwhelmed by extreme rainfall, floods, or storms, leading to system failure.


Water Quality Issues: Accumulated sediments can become a source of pollution if they release trapped nutrients, heavy metals, or organic matter back into the water.

            
Land Use Conflicts: Sediment traps may require significant space, which can conflict with other land uses like agriculture, urban development, or recreation.


High Costs: Designing, building, and maintaining sediment capture systems can be expensive, especially in urban or heavily engineered environments.

        








NbS co-BENEFITS AND THEIR INDICATORS








        

            
Improved Water Quality


Population trends of key indicator species. Presence of migratory bird species during critical seasons.


Enhanced Soil Fertility and Agricultural Productivity


Soil organic matter content (%), crop yield increases (kg/ha), nutrient levels in retained sediment.


Carbon Sequestration


Carbon sequestration rate (tCO₂/year), vegetation cover percentage (%).

            
Groundwater Recharge


Groundwater table levels (m), Recharge rate (mm/year).


Flood Risk Reduction


Reduction in flood frequency (flood events/year), water retention capacity of the system (m³).

        







COST ANALYSIS








        

            
Direct Costs


Design, engineering, construction ($50,000–$500,000 + $5,000–$50,000/year maintenance).


Indirect Costs


Land Acquisition, opportunity costs : $10,000–$1M (depending on land value and mitigation needs).


Time Horizon


1–5 years for implementation, 20–50 years for operation.

            
Direct Benefits


Improved water quality, flood control, erosion prevention


Indirect Benefits


Improved habitats for aquatic and riparian species, carbon sequestration, recreational value, agricultural productivity


Risk Assessment


Overload, sediment starvation, habitat disruption, high maintenance costs.

        











REFERENCES




South Korea, Seoul, Cheonggyecheon stream (sediment traps, vegetated wetlands).


Netherlands, port of Rotterdam, Sediment traps installed to manage sediment flow and reduce dredging.


 









IMPLEMENTATION OPPORTUNITIES




Thailand, Bangkok, Chao Phraya River, faces significant sedimentation and water pollution.


Malaysia, Port Klang, sedimentation in its navigation channels and berths, leading to frequent dredging.











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