Cutting dikes, cutting ties? Reintroducing Flood Dynamics in Coastal Polders in Bangladesh and the Netherlands

Renewed attention for ecosystem dynamics when considering flood related interventions has been instrumental in shaping initiatives to ‘de-polder' lands, i.e. returning previously reclaimed land to the waters. This is a substantial paradigm shift in land and water management, as poldering has been crucial to the development of both the Dutch and Bangladeshi deltas, where wetlands have been turned into productive agricultural areas by constructing peripheral embankments to separate water in rivers from water within polders.

Although these interventions have contributed significantly to increased food production and safer livelihoods within the embankments in the short run, negative socio-environmental effects also surfaced. Constructing flood preventive embankments also means preventing the deposition of sedimentation. As a consequence, soil subsidence and the increase of economic value in the built-up area behind the embankments, turned a 'high-incidence, low-consequence' flood risk situation into a 'low incidence – high consequence' one. It also led to changes in social structures, decision-making power and trade-offs between when and how much water is taken in or drained out – (re-)distributing hydrological risks between stakeholders. It is against this background that polder embankments have come in for strong criticism and reconsideration. They were cut, reduced in height, moved or even completely removed, in the cases central in this paper. As a result of such ‘de-poldering’, flood dynamics (riverine/freshwater or tidal) have reappeared in formerly enclosed lands. Proponents of ecosystem-based approaches to water and flood management have been instrumental in encouraging this practice.

This contribution describes and analyses two cases from the Dutch and Bangladeshi deltas, where these kinds of interventions have taken shape over the last 10–20 years. The article highlights the complexity and interaction between environmental, technological and socio-political drivers for (and against) dyke removal and restoration of flood dynamics to reduce flood disaster risk. The Dutch case emphasises how a de-poldering project had redistributive consequences, when farmers felt they had to pay the price for other people's safety from flooding. The Bangladesh case study shows how controlled tidal flooding addresses another water related risk: prolonged water logging within delta polders. Originating in a popular practice of the region, this DRR strategy met with varying degrees of success when implemented as a top-down intervention.