A global synthesis of the effectiveness of sedimentation-enhancing strategies for river deltas and estuaries

Abstract

Deltas worldwide are at risk of elevation loss and drowning due to relative sea-level rise. Management strategies to restore or enhance sedimentation on delta plains, Sedimentation-Enhancing Strategies (hereafter SES), are now being pursued in many deltas but there has been limited cross-disciplinary and cross-delta review. Here we compare 21 existing and planned SES, synthesizing their physical characteristics, funding, governance arrangements, stakeholder engagement, process of implementation, environmental impact, land use change, and potential for upscaling. Strategies exist at various scales, from ~0.05 km 2 - 500 km 2 . 79% of strategies are capable of outpacing high rates of sea-level rise. Cheaper strategies are limited to short term impacts and small spatial scales, while more expensive strategies can have longer lifetimes. Most strategies create wetlands and flood water storage. Some create opportunities for agriculture, aquaculture, housing, or recreational land use. Combinations of SES will likely be the most effective and sustainable method for maintaining elevation in river deltas. • River deltas require sediment to maintain their elevation • Several management strategies exist in river deltas to enhance sedimentation • Strategies vary in lifetime and size (from 10–100 years & ~0.05 km 2 - 500 km 2 ) • Nearly all strategies outpace projected future rates of sea-level rise • Combinations of strategies can effectively and sustainably maintain some delta area • Prompt implementation is desired to increase chances of long-term delta sustainability