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Sediment nourishment
Sediment nourishment, often referred to as "building with nature," is an innovative nature-based solution (NbS) designed to combat coastal erosion by strategically adding sand or mud to the shoreline. Unlike traditional "hard" engineering structures like sea dikes or concrete breakwaters, sediment nourishment utilizes natural forces—such as waves, tides, and currents—to redistribute added materials across a coastal system (World Bank, 2026). In the Mekong Delta (MKD), this approach is becoming critical as the region faces "sediment starvation" due to upstream damming and extensive sand mining (Marchesiello et al., 2024). Historically, the Mekong River transported approximately 160 million tons of sediment annually, but recent estimates show this has plummeted to roughly 42 million tons per year, leaving the delta's fragile coastline vulnerable to erosion rates of up to 50 meters annually (CTU Journal of Innovation and Sustainable Development, 2026; Marchesiello et al., 2024).
The mechanism of sediment nourishment in the MKD typically involves two main strategies: active beach nourishment and the "Sand Motor" concept. Active nourishment involves the mechanical placement of sediment directly onto eroded beaches or foreshores to restore their protective volume (MDPI, 2022). The "Sand Motor" or mega-nourishment, a concept recently shared through Dutch-Vietnamese cooperation, involves depositing a massive volume of sand in a single location, allowing natural coastal processes to gradually spread it along the coast over several years (VietnamNet, 2026). This method is often more cost-effective than repetitive small-scale nourishment and creates new habitats for biodiversity while providing long-term coastal defense (World Bank, 2026).
In the mud-dominated sections of the MKD, such as the Ca Mau Peninsula, sediment nourishment is frequently integrated with mangrove restoration. This "Building with Nature" approach uses permeable structures, like bamboo or brushwood fences, to reduce wave energy and trap suspended sediment (ResearchGate, 2024). By artificially or naturally increasing the sediment supply in these sheltered areas, the bed level is raised to an elevation suitable for mangrove seedlings to take root (The Nature Conservancy, n.d.). Once established, the dense root systems of mangroves further stabilize the newly added sediment, creating a self-sustaining coastal barrier that can keep pace with relative sea-level rise (ResearchGate, 2024; CTU Journal of Innovation and Sustainable Development, 2026).
Research indicates that sediment nourishment can be a superior tool for coastal protection compared to standalone hard measures. Numerical modeling studies in the Go Cong coastal zone have demonstrated that while breakwaters are effective at reducing wave height, they can sometimes cause unintended erosion in adjacent areas (MDPI, 2022). In contrast, nourishment provides a "winning tool" by replenishing the overall sediment budget of the coastal cell, thereby addressing the root cause of erosion rather than just its symptoms (MDPI, 2022). Furthermore, the implementation of a delta-wide "Sand Budget" by the Vietnamese government and WWF aims to manage these sediment resources sustainably, ensuring that nourishment projects do not further deplete the delta's dwindling sand reserves (WWF, 2026).