CHAPTER -8-Coastal Protection 8.1Introduction Coastal protection can be defined as the defense against flooding and erosion. Erosion of many coastal regions takes place due to sea level rise , the reduction in sediment supply from rivers to the coastal zone, storm waves, and the interruption of longshore sediment transport by man-made structures such as breakwaters, groins, jetties,... etc. This erosion may endanger the structural integrity or functional usefulness of a beach or any other coastal structure. 8.2Causes of Erosion Before embarking upon any method of coastal protection, it is important to identify and understand both the short- and long-term causes of coastal erosion. Failure to do this may result in the design and placement of- shore protection measures which actually accelerate the process that the protection measure was intended to improve. Although the most serious incidents of coastal erosion occur during storms, there are many other causes, both natural and man-induced, which need to be examined. Figure 8-1. Undermining of structures by storm waves, Marina-El-Alamein.
Introduction to Coastal EngineeringChapter 8CEI 451 Harbor, Navigation and Shore Engineering Dr. Hesham N. Farres 2 Natural causes of erosion are those which occur as a result of the response of the beach to the effects of nature. Man-induced erosion occurs when human activities impact on the natural system. Much of the man-induced erosion is caused by a lack of understanding and can be successfully improved by good coastal zone management. However, in some cases coastal erosion can be due to construction projects that are of economic importance to man. When the need for such projects is compelling, the coastal engineer must understand the effects that the work will have on the natural system and then try hard to greatly reduce or eliminate these effects through designs which work in harmony with nature. 8.2.1Natural Causes 126.96.36.199Sea Level Rise. A long-term rise in sea level relative to the land exists in many areas of the world. This rise results in a slow, long-term recession of the shoreline, partly due to direct flooding and partly as a result of profile adjustment to the higher water level. 188.8.131.52Variability in Sediment Supply to the Littoral Zone. Changes in the world's weather pattern that cause droughts can result in a reduction in the occurrence of floods on rivers supplying sediment to the coastal zone. 184.108.40.206Storm Waves. Steep waves from a coastal storm cause sand to be transported offshore with temporary storage in a bar or shoal. Later partial recovery of the beach may be made through natural transport of this material onshore by longer period, flatter waves. But, in most cases, some material is permanently lost into the greater offshore depths.
- Winter '13
- ayman zakaria
- Erosion, Coastal geography, Coastal engineering, Beach nourishment, Shore Engineering