China
Africa
Explore chapters and articles related to this topic
Coastal Erosion and Shoreline Change
Published in Yeqiao Wang, Coastal and Marine Environments, 2020
Beach nourishment is the most commonly employed response to erosion today, largely due to the negative aspects of hard stabilization. Beach nourishment simply involves the emplacement of sand to widen the beach. Although nourished beaches keep the natural ability to adjust to the dynamic ocean, their drawback is that they must be renourished frequently to maintain their width—as often as every 3 to 4 years. Carolina Beach, North Carolina, has been renourished more than 20 times since its first beach nourishment project.[11]
Coastal engineering
Published in P. Novak, A.I.B. Moffat, C. Nalluri, R. Narayanan, Hydraulic Structures, 2017
P. Novak, A.I.B. Moffat, C. Nalluri, R. Narayanan
Beach nourishment may be used as an alternative to the installation of, or in conjunction with, groynes for the protection of shoreline. It is deployed where the coastal areas experience loss of sediments without being replenished by littoral drift or where the purpose is to create a wider beach for recreation or land reclamation. Beach nourishment involves the supply of suitable materials from quarries, mines or from offshore by dredging to the shore and dumping at suitable places on the beach so that the sea action will distribute them to shape the required beach profile. The amount of material for recharge will depend on the rate of coastal erosion, environmental requirements, required beach shape and onshore–offshore movement of bed material. It is advisable to use material for beach nourishment with properties like sizes and grading similar to the native material at the beach. Usually flat average slope of beaches is made of finer sediments. The quantity of material and hence the annual cost including transport from the material source and dumping along the beach will dictate the cost of recharging the coast. Computational and physical modelling can give better understanding of the processes involved and hence better estimates of the recharge volume especially for larger schemes. Details of design of beach profiles with beach nourishment are clearly set out in Simm et al. (1996). Reference is also made to Shore Protection Manual (US Army, 1984), Davison et al., (1992) and Dean (2002).
Conclusions
Published in Enzo Pranzini, Allan Williams, Coastal Erosion and Protection in Europe, 2013
Enzo Pranzini, Lilian Wetzel, Allan Williams
techniques, which promote sediment deposition and evolution of the shoreline (Kunz, 1999), e.g. submerged groins to intercept sediments without shifting the longshore transport offshore, as occurs with traditional groins (Jackson et al., 2002). However, because of problems associated with hard engineering in the nearshore zone, not least cost and maintenance, alternative soft engineering techniques that work in conjunction with natural coastal processes have increasingly been used since the 1970s. The beach nourishment method for shoreline protection is a soft engineering solution, extensively used primarily for the benefit of tourism. Some 40 per cent of the EU population live on the coast and 60 per cent of EU holidaymakers go to the coast bringing in 75 billion per annum, the Mediterranean alone receiving 170 million visitors (EC, 2009). Although not a permanent solution, beach nourishment can be a sustainable way to manage coastal erosion, if coastal processes are appropriately considered. Following nourishment, the new wider beach serves as shore protection from the impacts of storms and increases recreational benefits with new tourism related opportunities (Benassai et al., 2001). Another soft engineering solution, which has been tested on eroding coastlines, is beach drainage (Turner and Leatherman, 1997). Bowman et al. (2007) showed moderate beach accretion and shoreline advance following installation of beach drainage at Alassio Beach, northern Italy. However, effectiveness of this method is governed by beach thickness and sediment type. All coastal protection decisions should be based on sound data.
Marine Geology and Sand Resources of the Southern North Carolina Inner Shelf
Published in Marine Georesources & Geotechnology, 2022
Ian Conery, John P. Walsh, David Mallinson, David R. Corbett
Like many areas around the world, the North Carolina ocean coast is experiencing widespread erosion as a result of reoccurring storm events (Luijendijk et al. 2018). The shelf geomorphology and geology play a key role in shoreline changes (e.g., Miselis and McNinch 2006) and also hold sand resources to mitigate against erosion. Beach nourishment is used worldwide as a strategy to combat erosion of sandy coasts (e.g., de Schipper et al. 2021). Often described as a “soft-engineering” strategy, nourishment is designed to dissipate wave energy and minimize storm surge to protect infrastructure and to sustain recreational beaches that are economically essential in tourism-driven areas. Along some sections of the U.S. Mid-Atlantic Coast nourishment occurs every few years. For example, since 1939, nearly $850 million has been spent in North Carolina (NC) on nourishment of > 250 projects and > 250 miles of coastline (PSDS 2018).
Modelling the cross-shore profiles of sand beaches using artificial neural networks
Published in Marine Georesources & Geotechnology, 2019
Isabel López, Luis Aragonés, Yolanda Villacampa
On the other hand, for evaluating the performance of the model, various statistical parameters were studied (Eqs. 4, 5 and 6). By analysing these parameters, it was observed that the neural network improves the results compared to actual models (Dean and Aragonés). Thus, it was observed that the mean absolute error of the ANN (for all profiles, training and test data together) is 81.2% and 55.5% lower than Dean (0.22 m vs. 1.16 m) and Aragonés (0.22 m vs. 0.49 m) models, respectively. The MAPE and the percentage relative error also exhibit an improvement over the numerical model of Aragonés; these errors were 64.0% and 71.3% lower. By analysing in detail the errors, it could be seen that the greatest errors occur mainly on the beaches 30, 33, 42, 65, 81 and 102. After the study of the inputs used in the profiles of these beaches (sediment, slope, morphology of the Posidonia meadow, etc.), no anomalous value was observed or that stood out with respect to the average of values used in the rest of the profiles (Table 3). However, these beaches presented the following singularities: (i) Beaches with important nourishments (Figure 6(a,c)), therefore, perhaps the profile has not yet stabilized. (ii) Beaches with rock reefs or islets in front of their coasts so the bathymetry is considerably altered, and therefore also the profiles are (Figure 6(b,d)). These kinds of profiles represent only 5.5% (23/418) of the studied profiles, so the network is not able to learn effectively their singularities. In order to correct this problem, there are two options: (a) remove these profiles from the ANN and (b) increase the sample size of data by Monte-Carlo simulations or by perturbing the input by say 5/10% or similar, however, given the extent of the work this is left for future work. Nevertheless, the results obtained by the ANN in this area are lower than both Dean’s formulation (72.7% absolute error, 65.4% MAPE and 88.3% percentage relative error) and Aragonés model (36.9% absolute error, 30.0% MAPE and 82.5% percentage relative error; Figure 5). The improvement in the accuracy of the profile results in a smaller volume error when calculating the amount of sand needed in beach nourishment, and therefore a lower economic cost, about 5.3–9.8 €/m of beach (assuming a cost of 11.5 €/m3; López, Aragonés, Villacampa, and Compañ 2017). This cost savings certainly compensates the largest computational cost of the ANN versus the simplicity of the numerical models and the formulations.