Nature-based solutions for reducing flood risk: A case study in South Tongu district, Ghana

Indicated issues

Displacement, infrastructure damage, and livelihood loss

Flooding poses a significant threat to socio-economic and ecological systems in Ghana, particularly in rural districts such as South Tongu. Frequent and severe flooding are caused by a combination of heavy rainfall, poor drainage, and upstream dam operations. The flooding leads to displacement, infrastructure damage, and livelihood loss. Conventional flood control measures such as drainage systems and zoning have proven inadequate in managing the recurring floods.       

Goals

The effectiveness of implementing NBS

The project aims to assess the effectiveness and practicality of implementing Nature-Based Solutions for flood risk management in South Tongu district.

Specific goals include:

1. Identifying current flood-prone areas and underlying causes.
2. Modelling and comparing the impact of three selected NBS measures (permeable surfaces, river restoration, and riparian/forested buffers) using the FastFlood model.
3. Evaluating the technical, economic, and policy feasibility of implementing these NBS measures in the South Tongu district.

Results

High technical effectiveness

All three NBS measures significantly reduced flood extent, depth, and the number of affected buildings. River restoration demonstrated the highest technical effectiveness, particularly in reducing peak flows along the Volta River. Riparian buffers also delivered measurable reductions, while permeable surfaces proved most effective in compacted urban zones. However, effectiveness alone does not guarantee implementation.

Practicality assessment revealed high technical feasibility but highlighted barriers such as limited funding, weak institutional coordination, and low stakeholder awareness.

Overall, the study demonstrated that NBS can complement existing structural measures and provide sustainable, cost-effective flood mitigation in rural Ghana.

Valuation of solutions

The study evaluates the effectiveness and practicality of NBS for managing flood risk in the South Tongu district of Ghana. The aim was not only to assess the hydrological performance of selected NBS, river restoration, permeable surfaces and riparian/ forested buffers, but also to examine how local socioeconomic conditions, policy frameworks and institutional capacities influence their feasibility in practice.  While the modelling results demonstrate that NBS can reduce flood extent, depth and building impacts under various scenarios, their practical adoption faces significant constraints.