Frequent flooding is one of the consequences of the changing climate that is affecting most communities in Sub-Sahara Africa. When it rains it pours, and Narok County in the Southern parts of the Great Rift Valley in Kenya is a good example. Situated within the Valley of the Great Rift Valley Narok Town and Masai Mara National Reserve are hot spots for flooding during the rainy seasons in Kenya. The intense rains leave no time for the water to infiltrate leading to flooding. Passing through the Narok Town and Masai Mara National Reserve is the Enkare Narok River which floods due to heavy rainfall uphill in the Mau Forest the largest water tower in the Country.
In order to safeguard life and properties of the community, informed decision making based on accurate rainfall forecast is a key ingredient. Numerical weather prediction (NWP) models plays a key role in flood forecasting. Using the WRF model, KMD has established a limited area model with the outer nest extending into Central Africa to take care of the unstable Congo air mass and into the Indian Ocean to cater for the ocean dynamics running at 10 km resolution. The inner domain running at 2 km resolution extends from the Lake Victoria basin through the Rift Valley and the Highlands east of Rift valley. Shown in figure 1.
The model is run daily from 0600Z with initial conditions from the GFS model. The model output is then analysed and flood risk generated from the rainfall amounts expected bearing in mind the soil saturation status from the previous day precipitation.
This information is shared to the farmers, disaster managers and other stakeholders through the WhatsApp group to inform their decision making.
Figure 1. WRF domains; Outer domain at 10 km and
inner domain at 2 km horizontal resolution.
Figure 3 An Example of Flood Early Warning Service (FEWS) for Narok County
Figure 2. WRF Rainfall output for Narok County
With the success stories from Narok County, the Flood Early Warning Service (FEWS) will be rolled out in other Counties such as Isiolo, Nakuru and Muranga through the TEMBO project.
Authors: Kizito Amua and Dr. Richard Muita
Date: 1st September 2023
This project has received funding from the European Horizon Europe Programme (2021-2027) under grant agreement n° 101086209 (TEMBO Africa).
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