Flood risk assessment for the lower Zambezi watershed
Problems
In the past decades, and particularly in recent years, it has repeatedly become clear that in large parts of Mozambique communities, businesses and ecosystems are extremely vulnerable to floods. The devastating flood events of 2019 as a result of cyclones Idai and Kenneth may have been the most extreme ever recorded in the area, and under the projections of climate change such events could become more common in the future. There are indications that a changing climate may lead to increased frequency and strength of severe rainfall events associated with cyclones that reach Mozambique’s coasts. Therefore, the urgency is higher than ever to understand the hydrology of the basins, to identify locations that are vulnerable to floods and, next, to develop preparation, protection and other flood risk-reducing measures that are realistic, sustainable and, most of all, effective.
Solutions
In response to this challenge, Resilience performed, together with project partner HKV, a flood risk assessment for the Lower Zambezi area in Mozambique. This assessment served as a preliminary study for the ECO-DRR project of the Mozambican Red Cross (CVM), supported by the French Red Cross (FRC) and funded by the French Development Agency (AFD). The flood risk assessment consisted of a desk study, stakeholder consultation, hazard and risk assessment, and fieldwork. The desk study examined historical flood risk, with an additional emphasis on local coping capacity and the ecological situation related to floods in the Lower Zambezi. Stakeholder consultation was performed through interviews, workshops and field visits. To assess the impact of natural hazards in the target area, a hazard study was performed, consisting of the assessment and mapping floods, erosion and landslides. The risk study then focused on flood risk, through the mapping of assets, modelling of affected areas with different flood scenarios (using various return periods), and a quantification of damages per flood scenario. During the fieldwork, target areas were visited together with local stakeholders to get a better understanding of the situation on the ground, which was used to verify desk study and modelling results.
Impact
Following the findings of the flood risk assessment, several recommendations for physical as well as non-physical measures are formulated, including an estimation of costs and impact of measures. The physical measures focus on the safety of key assets such as roads, schools and hospitals. Existing dikes have created a sense of safety for certain areas, which is unjustified in the absence of proper dike maintenance. Regarding non-physical measures, the main idea is that having access and evacuation routes and safety shelters are needed preconditions to deal with flood emergencies. The next step is to inform the population on what to do before, during and after an emergency. Based on these recommendations, FRC and CVM will further shape the implementation strategy of ECO-DRR together with local partners.