Beach scraping is recovering material from the berm at the foreshore and placing it on the backshore at the foot of the dunes or the cliff.
Beaches consisting of coarse sand or gravel sometimes form a beach berm (a nearly horizontal plateau on the beach face or backshore, formed by the deposition of beach material). This berm can be removed and placed on the backshore or the foot of the dunes, which is understood as beach scraping. The purpose of beach scraping is the strengthening of the upper part of the beach. In case of storms, this material will be firstly eroded and thus protect dune or cliff systems.
It differs from beach nourishment because new volumes of sand are not introduced to the system replacing eroded material. Instead, sand is moved from one location on the beach to another (Kratzmann et al. 2008).
This technique is used to move small volumes of accumulated sand to the upper beach. It is important to remove only that quantity of sand that can be replenished naturally. This is why beach scraping should rather be executed at beaches mainly exposed to seasonal erosion. For beaches exposed to long-term erosion, this measure seems not feasible, because in this situation the measure would not contribute to the overall stability of the beach profile.
If undertaken in situations where sand has been accumulated over a period of time repeatedly, the technique can increase the volume of the dry beach, providing some mitigation for short-term erosion. (Harrington 1994).
Comparing to other coastal defense measures (like building a dyke or groynes), this approach has relatively low derogation on the ecological system. For example, for a beach scrapping undertaken in New Brighton Beach, Byron Shire (AUS), there was a environmental assessment undertaken, stating that “is not likely to cause significant adverse impacts on threatened species identified as potentially occupying the proposed works area” if the works are carried out during winter time.
But the relocation of sand with heavy machines will always have an impact on the ecosystem. Therefore a environmental assessment before the measure is undertaken und a monitoring of the impacts during afterwards should be mandatory. In New Brighton Beach this assessment of the impacts of the measure on macroinverrtebrates were undertaken (see Smith et al. 2011). The results of the study show that the beach scraping had no on the biodiversity and assemblage patterns of beach infauna. The authors assume that the primary reasons for the lack of impact are likely related to the high energy wave environment and high natural levels of dynamism at New Brighton beach, and the fact that deposition of scraped sand did not cause major changes to beach granulometry. This may lead to the conclusion that at beach with a natural high dynamics the ecosystem is already adapted to drastic changes.
Political & social feasibility
Beach scraping can only take place at sandy beaches, which are often frequently used by tourists and thus providing a source of income for neighboring communities. A mechanical restructuring of the beach may disturb recreational activities. Therefore it is recommended to undertake the measure in times of low touristic activity if possible.
Cost of implementation & maintenance
Beach scraping is a rather short-term techniques and needs subsequent maintenance. In the study mentioned for New Brighton Beach1, a cost-benefit analysis was also undertaken. These showed that benefits to costs ratio are rather high. This is mainly due to the benefits arising from tourism and beach scraping is a potentially cheaper form of beach nourishment. The numbers refer to a proposal of a beach scraping, which was planned for approximately 1.5 kilometers. A scrape depth of up to 0.2m was recommended and a total cost of around 160000AUD$ (ca. 10700€) were estimated. These costs included for example On-ground works, ecological and coastal engineering supervision, biological and dune monitoring, and dune rehabilitation works.
If undertaken correctly, Beach scraping can strengthen the beach to slow down erosion. Like beach nourishment this measure doesn’t eliminate the causes for erosion and needs repetitive intervals. But with rather low ecological impacts and financial costs it is a valuable prevention measure.