Mauritania and Senegal coastal area urbanization, ground water flood risk in Nouakchott and Land use/land cover change in Mbour area

Abstract

Urbanization has increased significantly in Mauritania and Senegal during the last decades since the countries gained independence. In both countries most of the important cities are located in their coastal area. Cities inherited from the colonial period expand both in size and inhabitants. The total urbanised surface has increased at a rate of 300- 400 % in 30 years. The development of cities impacts the coastal environments, particularly the ground water flow in the city of Nouakchott in Mauritania during the rainy season and the land cover and land use in the city of Mbour, located in the coastal area called Petite Côte in Senegal. This study used GIS and RS techniques to map the expansion of urban area over the Mauritania and Senegal coastline and measure the rate of expansion during the last decades. A linear regression analysis revealed a strong relationship between the urban area expansion and population growth in both countries’ capitals. In Dakar, the capital of Senegal, the urbanised area increase rate is estimated at 291 % between 1978 and 2002. The correlation has a R₂–value of 0.94 that indicate a strong relationship between the two variables. Using the same techniques, the environmental impacts of urbanization was evaluated. Classification and reclassification of Nouakchott elevation identified suitable and unsuitable areas and this data was used to estimate the extent of built-up construction in low-lying areas that may be influenced by ground water flooding during the rainy season. These surfaces represent 13.66% of the urbanised area in 2008 with a population of 112 964 inhabitants. To evaluate the change in land cover/land use in Mbour area located on Petite Côte (Senegal), Landsat 5 TM anniversary images of 17th October 1984 and 22nd October 2009 were used. Supervised classification method was used after defining training sites. Image classification was done using maximum likelihood classification. Post classification was used to evaluate the changes. The rates of changes were calculated. The results show that urban area, rain fed cropland, mosaic cropland vegetation and sparse vegetation increased at a rate of 490.04%, 27.02%, 30.21%, and 23.17 % respectively. Open shrubland decreased by an estimated of 85.69%. Landsat NDVI statistics showed no significant change in greenness but changed vegetation patterns were detected by visual analysis. NOAAH/AVHRR time series and rainfall data were extracted and analysed. The correlation analysis indicated a strong relationship between NDVI and rainfall data in Mbour area. The LU/LC map was compared to Landsat NDVI and NOAAH/AVHRR time series and rainfall data by visual analysis. The results indicated that urbanization had effect on LU/LC in the Mbour area and that the degree of greenness was more a function of rainfall. The change in Landsat NDVI pattern is related to land use change.

Abstract

Popular science
Mauritania and Senegal are two countries located at the border of West Africa. Their urban population is increasing significantly since the last decades because of rural immigration and natural growth of urban population. Using GIS and remote sensing techniques, the rate of urbanized area is estimated for two coastal cities of Mauritania (Nouadhibou and Nouakchott) and for three coastal cities of Senegal (Saint Louis, Dakar and Mbour). The results show that the urban area is increasing significantly at the rate of 200 - 300 % in 30 years.
In the second part of the study, still using the same techniques some environment impacts due to urbanization are estimated in the city of Nouakchott in Mauritania and in the city of Mbour in Senegal. Nouakchott urban area susceptible of inundation due to ground water flow disturbance is estimated and Mbour ´ s land use, land cover change is evaluated.
The result reveal that in Nouakchott the urban area susceptible of inundation due to building construction in low lying area represent 13.66% of the urbanized area in 2008 and 112 964 inhabitants are leaving there. Land use, land cover change study results shows that urbanization had effect on land use, land cover in the Mbour area and that the degree of greenness was more a function of rainfall.

• author: Ouattara, Adama
• supervisor: Ulrik Mårtensson; Sébastien Gadal
• organization: Dept of Physical Geography and Ecosystem Science
• course: NGEM01 20102
• year: 2011
• type: H2 - Master's Degree (Two Years)
• subject: Earth and Environmental Sciences
• keywords: geography, physical geography, urban area expansion, coastal area, population, ground water flood, land cover/land use, normalized difference vegetation index, geographical information system, remote sensing.
• publication/series: Lunds universitets Naturgeografiska institution - Seminar series
• report number: 227
• language: English
• additional info: External supervisor Sébastien Gadal,; Maître de conferences UVSQ-OVSQ (REEDS Lab.); Co-Head of the Department of Geography; Head of the Master TGAE; NASA Scientific Advisor; Université de Versailles/Saint-Quentin
• id: 3015245
• date added to LUP: 2012-08-29 16:31:46
• date last changed: 2012-09-24 13:39:49