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Climate change and Urban Vulnerability in Africa

Climate change and Urban Vulnerability in Africa. Assessing vulnerability of urban systems , population and goods in relation to natural and man-made disasters in Africa. Course on Hazard , Risk and ( Bayesian ) Multi-risk assessement Napoli 10/24/2011 – 11/ 11 /2011.

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Climate change and Urban Vulnerability in Africa

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  1. Climate change and Urban Vulnerability in Africa Assessingvulnerability of urbansystems, population and goods in relation to natural and man-made disasters in Africa Course on Hazard, Risk and (Bayesian) Multi-riskassessement Napoli 10/24/2011 – 11/11/2011 Module 5: Case study: from climatic data to flooding risk assessment - Application for informal settlements Prof. F. De Paola, prof. F. Jalayer, ing. R. De Risi

  2. MOLFETTA F. De Paola

  3. BasinmainCharacteristics • Area S [Kmq] • Lengthofmainchannel [Km] • Medium Slope • Drainage density DD • Averageheight F. De Paola

  4. CN method The runoff curve number CN is an empirical parameter used in hydrology for predicting direct runoff or infiltration from rainfall excess. The curve number method was developed by the USDA- Natural Resources Conservation Service, which was formerly called Soil Conservation Service or SCS. The number CN is still popularly known in the literature as a "SCS runoff curve number". The runoff curve number is based on the drainage basin characteristics (hydrological soil group, land use, land management) and hydrological condition. References, such as from USDA, indicate the runoff curve number for characteristic land cover descriptions and a hydrologic soil group F. De Paola

  5. CN method • where: • - Pnet : accumulated runoff depth (mm) • - P : accumulative rainfall depth (mm) • - Ia : initial abstraction (mm), or the amount of water before runoff, such as infiltration, and rainfall interception by vegetation • - S : potential maximum soil moisture retention after runoff begins (mm). • Assuming Ia = 0.2S Maurizio Giugni CN fundamental relationship: 17/11/2011 F. De Paola 5

  6. CN method The runoff curve number, CN, is then related to potential maximum soil moisture retention, S, by: CN has a range from 30 to 100. Lower numbers (permeable soils with high infiltration rates)indicate low runoff potential. Larger numbers are for increasing runoff potential. Maurizio Giugni 17/11/2011 F. De Paola 6

  7. HydrologicSoil Group Curve Numberbased on hydrologicalsoilgroups: Group Aiscomposedofsoilswithvery high infiltration rate and low runoffpotential Group Bsoilswith high infiltration rate whenthoughlywetted and moderate runoffpotential Group Csoilswith low infiltration rate and moderately high runoffpotential Group Dsoilswith low infiltration rate evenwhensaturated and high runoffpotential F. De Paola

  8. F. De Paola

  9. LAND USE MAP F. De Paola

  10. Average on the area F. De Paola

  11. CN F. De Paola

  12. Peak hydrograph (Mockus) L [km]; s[%] tl: catchment lag time (time between the hydrograph centroid and the net rainfall centroid) • V [mm] • A [km2] • ta [h] F. De Paola

  13. 17/11/2011 F. De Paola 13

  14. F. De Paola

  15. Inundationmodel Depth-averaged shallow water equations on land surface F. De Paola

  16. Two - dimentionalModel F. De Paola

  17. T = 30 YEARS F. De Paola

  18. T = 200 YEARS F. De Paola

  19. T = 500 YEARS F. De Paola

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