The Process of Coastal Erosion and its Economic Implications for Delmarva
Many geologic processes affect the landscape of the Delmarva Peninsula drastically, but one specific process has major economic implications as well. The process of coastal erosion, which is defined as the actual removal of sand from a beach to deeper water offshore or alongshore into inlets, tidal shoals and bays, is one of the most detrimental geologic events to this region’s economy (Scientific American). This type of erosion can result from many factors including rising sea levels and changing weather patterns. A majority of coastal erosion is episodic, meaning that the erosion occurs in small episodes over short periods. During intense storms, such as hurricanes or nor’easters, the coastal shoreline can be eroded in a day or even several hours. Erosion is also sporadic, meaning that erosion rates in the same region are not always uniform (Stewart). In the Delmarva region, the beaches are a main recreational attraction, and the resulting tourism boosts the economy. Therefore, when these geologic events do occur, the primary concern of governments in these areas is beach replenishment. Beach replenishment is a costly endeavor, but a necessary one. Some recent replenishments in southern Delaware have been in the range of 3 to 5 million dollars, and are not guaranteed to last. As a result, it is important to understand the process of coastal erosion as well as the replenishment techniques in order to maximize the economic benefits of the Delmarva beaches.
Coastal erosion results from interaction between ocean waves beach sediments. Human influence, mainly urbanization, also plays a large role. Beach systems are considered to be in dynamic equilibrium and are essentially temporary geological features. The sand levels on beaches are constantly in flux. The common misconception is that once sand is removed off the beach back into the ocean, it is lost. However, when sand is moved from one location to another it is simply recycled and returned into the system. For example, winter storms may remove significant amounts of sand, creating steep, narrow beaches. In the summer, gentle waves return the sand, widening beaches and creating gentle slopes (Haznet). The many factors involved in coastal erosion, including human activity, sea-level rise, seasonal fluctuations, and climate change, allow sand movement rates to change year to year. Between 80 to 90 percent of sandy beaches are currently in erosion cycles at rates ranging from only a few inches to over 50 feet per year, but the issue that causes beachgoers concern is the idea that this cyclical behavior is not balanced in equilibrium, and the erosion in the winter outweighs the sand return in the summer. (Haznet) Below are pictures of beach erosion in Bethany Beach, Delaware. The picture on the left (Figure 1) is erosion following Hurricane Isabel in 2003, while the picture on the right (Figure 2) is erosion following the 2009 Nor’easter.
The process to mask some of the effects of beach erosion is known as beach nourishment. Beach nourishment, or replenishment as it is commonly referred to, is the process of dumping or pumping sand from elsewhere onto an eroding shoreline to create a new beach or to widen the existing beach. Many times, a dredge removes the sand from a borrow site in the ocean and delivers sand to the beach using pipes. The sand arrives on the beach in the form of slurry, which is a mix of sand and water. The slurry is then moved to the desired locations on the beach using heavy-duty machinery. This process does not prevent erosion from occurring in the future, however it simply adds additional material that was lost. As a result, this process is repeated continually in order to maintain the beach (Barber). Each nourishment is expected to have a lifetime, meaning that the nourishment will wear away eventually. Lifetimes of nourishments are difficult to predict because of the...
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