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FEATURE: Town planning gets boost from new Africa-focused climate model

A new climate model developed by researchers working for the Future Climate for Africa programme (a sister programme of CDKN’s) will provide local planners with more useful projections of the climate in their area for the coming decades. Leonie Joubert reports.

The Kenyan town of Nyandiwa sits on a small peninsula that juts out from the eastern shore of Lake Victoria. Like so many towns on the banks of the lake, it will become ever more vulnerable to flooding and inundation as its infrastructure struggles to cope with more intense storms and possible rising water levels in the lake.
Until now, if town planners wanted to get a picture of how rainfall patterns here might change in future, in order to manage infrastructure planning like building better stormwater management systems or flood-resilient roads, they could only look to computer models that painted a broad-strokes picture of the wider region’s changing climate. Most climate models use a 100km by 100km grid. But this doesn’t give details that are fine-grained enough to help town planners understand what is likely to change for a settlement as small as this Nyandiwa, which is about 2.5km long, less than a kilometre wide, and hemmed in on two sides by the lake’s shores.

But a new climate model will change this. The Pan-African Convection-Permitting Regional Climate (CP4-Africa) model zooms in to a 4.5km by 4.5km grid, and allows climate researchers to take a much closer look, on a scale that’s better suited to the local-level needs of a town like Nyandiwa.Convection, the upward flow of warm air in the atmosphere, is the engine that drives cloud formation, rainfall, and thunderstorm activity across the region. The CP4-Africa model works specifically to simulate how these convection patterns will change in future, and what that will mean for the timing and intensity of rainfall patterns and big storm events over the Lake Victoria Basin.

It is relatively easy to project how temperatures will respond to rising carbon dioxide levels in the atmosphere using computer models, explains Zablone Owiti, a research fellow with the Future Climate for Africa (FCFA*) project. But modelling how this will change air movement, and ultimately the formation of clouds, rainfall or storm patterns in future, is much more difficult, particularly at a more local scale.

‘The CP4-Africa model allows us to zoom in closely over the Lake Victoria Basin area. We can now simulate air movement on a much smaller grid, and get an idea of how this will impact on the duration and intensity of rainfall and storm events in future,’ he says. For instance, the model can project changes in statistical properties of rainfall patterns for a decade-long window in the near-term, such as from 2020 to 2030, or far in a decade in the longer-term future, such as 2090 to 2100.

The kind of climate information generated by this modelling can help town planners, development practitioners, and hydrologists understand the implications of changing rainfall and storm activity in terms of inundation and flooding most likely to occur along the shores of Lake Victoria. They will be able to identify places that are most vulnerable, and draw up risk maps to guide planning.

The Lake Victoria Basin is also the economic engine room of East Africa. Countries like Kenya, Uganda, and Tanzania rely heavily on rain-fed agriculture and fresh-water fishing in the lake.

‘This kind of information can help support the agriculture sector to adapt, as well. What sort of crops should they prioritise, in anticipation of local-level changes in rainfall? What alternative farming practices will help farmers to be more resilient? These can help farming policy decisions at national level, which can trickle down to farmers on the ground.’

Towns and settlements around the Lake Victoria Basin region in East Africa, like Nyandiwa on the Kenyan shore of the lake, need climate change information that is detailed and specific to their smaller-scale planning needs. Source: Google Maps

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