The Effects of the Fourth Dike on the Kim Đông Coastal System
Balancing Flood Protection, Ecosystem Resilience and economic development in Vietnam’s Coastal Zone
M.K.J. van den Heuvel (TU Delft - Technology, Policy and Management)
T.J. Kaalberg (TU Delft - Civil Engineering & Geosciences)
L.J. Selders (TU Delft - Civil Engineering & Geosciences)
Tijn Spijkers (TU Delft - Civil Engineering & Geosciences)
B.B.J. Velthuijs (TU Delft - Civil Engineering & Geosciences)
S.A.M. Windhorst (TU Delft - Civil Engineering & Geosciences)
E. Minkman – Mentor (TU Delft - Technology, Policy and Management)
C. Mai Van – Mentor (TU Delft - Civil Engineering & Geosciences)
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Abstract
The completion of a fourth sea dike (Binh Minh 4) in Kim Đông, Ninh Bính, in Vietnam will reshape local hydrodynamics and will result in land reclamation. Thus, the balance between mangrove forest health, flood protection, local livelihoods and development goals will be changed. This report addresses the impacts and fills knowledge gaps regarding the completion of this fourth dike on hydrodynamics in Kim Đông, and examines hydrodynamic, ecological, governance, and social factors in relation to the mangrove ecosystems in the region.
To achieve this, a governance analysis and system analysis are combined with a hydraulic analysis and a conceptual hydrodynamic model in Delft3D. This approach is supported by literature and institutional reviews, expert interviews, a community survey, and hydraulic data, including satellite-derived wave and wind records, as well as field measurements. Together, these elements shape the model set-up, boundary conditions and interpretation. The modelling framework compares a baseline situation without a dike with two with-dike scenarios, simulating both storm and regular weather conditions. Physical changes in the model are linked to drivers of ecological change, allowing an assessment of their impact on mangrove forests and socio-economic conditions in the area.
Findings from the conceptual Delft3D model indicate that the completion of a fourth dike is likely to reduce tidal connectivity and sediment supply to the enclosed area, leading to longer inundation times and lower water levels. These change in conditions drive mangrove squeeze, reducing habitat, shelter and carbon storage potential. At the same time, land reclamation creates development opportunities for aquaculture. Interventions to mitigate the effects of the fourth dike are presented using a COCD box, and evaluated via a multi-criteria analysis. Suitable interventions are further elaborated on their trade-offs and implementation process.
Decision-making in Vietnam, and in Kim Ðông especially, is highly hierarchical, which limits involvement of local authorities and residents even though they are most affected. Conflicting priorities among sustainability, economic growth and climate adaptation further complicate this involvement in decision making. Additionally, limited data availability and experience with nature-based solutions also constrain adaptive management and long-term monitoring. With this in mind, four potential interventions are assessed: adaptive gate management, mangrove co-management with incentives, sustainable aquaculture \\certification, and a digital monitoring platform. No single measure resolves all challenges. However, co-management with incentives and sustainable aquaculture emerge as promising options that couple ecological restoration with socio-economic benefits, supported by adaptive gate operations and a digital platform to improve coordination and transparency.