Concept
Sedimentation enhancing strategies are environmental management projects aiming to restore and facilitate land-building processes in deltas. Sediment availability and deposition are important because deltas naturally subside and therefore need sediment accumulation to maintain their elevation, particularly considering increasing rates of sea-level rise. Sedimentation enhancing strategies aim to increase sedimentation on the delta plain primarily by restoring the exchange of water and sediments between rivers and low-lying delta plains. Sedimentation enhancing strategies can be applied to encourage land elevation gain to offset sea-level rise. Interest in sedimentation enhancing strategies has recently increased due to their ability to raise land elevation, which is important for the long-term sustainability of deltas. When compared to conventional flood protection infrastructure such as embankments and seawalls, sedimentation enhancing strategies provide various benefits. Firstly, flood protection structures can exacerbate environmental problems in deltas: land reclamation and levee construction result in a loss of water storage area during peak river discharges, which may cause an increased risk of flooding further downstream. Embankments also exacerbate land elevation loss due to soil drainage and hinder natural sediment accumulation. In contrast, sedimentation enhancing strategies do not cause these problems and instead address multiple issues simultaneously: they reduce flood risks while simultaneously restoring ecosystems, enhancing production (e.g. fisheries) and cultural (e.g. landscape) ecosystem services. Sedimentation enhancing strategies are also more flexible than conventional flood protection. Large-scale infrastructural flood defences are costly and rigid, requiring considerable investment to adapt infrastructural flood defences to changing boundary conditions. Particularly considering uncertain future scenarios due to climate change, sea-level rise and peak river discharges, rigid flood defences may not be the optimal choice.
