Coastal erosion project, Diani beach, Kenya

Master project report. Since the seventies, the establishment of hotels and other facilities has increased the pressure on the Kenyan coast. During the last decade, hotel managers and residents in Diani Beach have been experiencing problems with erosion. The only measures taken to address the problem are individually built seawalls to protect private properties. These seawalls are mostly not properly built and do not decrease the erosion rate. Erosion continues and beaches are still disappearing. In some places, coral rock is exposed or buildings collapse. The economy in Diani Beach is strongly depending on tourism. A white beach with a gentle slope and a flourishing ecosystem of lagoon and coral reef is desirable to attract tourists. The current situation in most parts of Diani Beach is far from desired. Diani Beach seems to be subject to structural erosion, due to several reasons. Initially, the narrowness of the African continental shelf leads to an easily loss of sediment into the deep ocean. Also the fact that there are no high mountain ranges along the Kenyan coast results in a low rate of sediment flowing into the ocean. A lack of sand combined with the relative stableness of the African crustal plate can be seen as causes for structural erosion. In Diani Beach the process is accelerated by a number of factors, both human and nature induced. Measures have to be taken to recover and maintain the desired situation. However, it is difficult to determine the optimal solution because of policy issues and lack of data. Several measures are proposed, which can be divided into three categories: management and policy measures, soft measures and hard measures. The first category implies e.g. determination of the setback line, altered approach to fishery and enforcement of legislations. Soft measures include planting of vegetation and beach nourishment. Breakwaters, groynes and improvement of seawalls are hard measures. A combination of measures can have effect on both short and long term, first recovering and subsequently maintaining the desired situation. However, more data have to be gathered to determine the best combination of measures, make a proper design and find the way to implement them.