Climate Change and Flood Assesment : A Future towards NWP
Case Study: Rwanda
1. Country description
In the continent of Africa (latitude 01-58S, longitude 030-07E) , Rwanda covers 24,668 Km2 of land and 1,670 Km2 of water. The total area of 26,338 Km2 .
The climate is a tropical temperate climate. The average precipitation per annum in Kigali(Capital City) observed between 700 and 1200mm
2. Rainfall Patterns and Types of Flood
3. Influence to Flood dynamics
•Rainfall variability: is the most important factor in creating flood, but there are many other contributing factors such as:
- Land use : land used is dominated by agriculture and small forest
plantation as well as small open lands
-Topography : The area is a characterized by mountains and deep valleys
- Drainage systems: Can lead to flood when drainage systems cannot deal with voluminous amount of runoff water (Douglas et al.2008) and this is the case in Kigali city
- Waterways: water flow path such as river, tributary or stream that captures runoff and conveys it towards an outlet
- Soil Texture: The valley is characterized by low infiltration clay soils
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Figures illustrating the risk zone of flood in the capital city,the topography of Rwanda,land use and soil map of Nyabugogo which is one the most flooded area in Rwanda
4. Discussion on the Analysed Data
The available rainfall data collected were daily measurements synoptic data. Among all available rainfall stations, one station was chosen because it had no missing data: Kigali aero located at latitude -1.95, longitude 30.11 with an elevation of 1495m.
15 years (1999-2014) data were analysed to show the rainfall distribution in 15 years and which monthly average rainfall amount may lead to flood in Kigali city based on some reports and news on flood occurrence in that city.
The 15 years data were plotted using both R and Excel to show monthly rainfall variability and the probability of excedence of annual rainfall as shown in the figures below
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It was found that the months susceptible to get high amount of rainfall are march and april during the long rainy season, as well as october and november during short rainy season,with a monthly average rainfall amount variating between 3 to 8mm
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Since the precipitation is very low, it is important to consider other factors contributing to flood in the area such as soil texture and drainage system in the area.
For this study, the proposed adaptation measures and future work suggestions are found in the respective sections.
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