Medium-scale of the order of 5 million m3 — depending on the local context nourishments of channel walls, on locations where tidal channels erode the coast. This type of nourishment has successfully been applied in among others the Netherlands to keep the channels away from the coast. Large scale nourishment. The Sand Motor involves the placement of sand in the shoreface and above. It is supposed to function as a source of sediment supply re-distributed by waves and currents to beaches and dunes over distances of several kilometres.
It is meant to function over a period of some twenty years. The Sand Motor differs from traditional techniques both in terms of scale and by the sand redistribution technique mainly using the natural forces of wind and waves rather than mechanical energy.
Techniques also differ according to the origin of the sand deposit: Inland sources: the sand is excavated from accumulating areas close to the shore and transported to beach by trucks. This technique is more suited for small scale nourishment. Offshore dredging: the sand is dredged from the seafloor. Dredged material can be pumped through pipelines directly to the beach or can be suction-dredged from source, transported and dumped by ship or pumped ashore to build up beach profiles.
Offshore dredging should be used carefully and should not be done in the submerged beach close to the coast to avoid impacting beach dynamics.
Category Green. Stakeholder participation Stakeholder participation will depend on the specific case and on the national context.
Success and Limiting Factors Success factors: Beach nourishment is a flexible and fast coastal management option compared to hard construction, and it is adaptable to changing conditions.
Due to its flexibility it is also a relatively cheap measure to prepare, as long-term design criteria usually are not taken into account, something necessary for hard construction. If conditions change in a negative way, additional nourishment can be simply added.
Beach nourishment can complement other grey measures such seawalls or groynes and green measures such as dune reinforcement. Dune construction and reinforcement can even improve beach resilience and act as sand reservoirs, thus improving effectiveness of beach nourishment.
Besides flood and erosion protection, beach nourishment can provide benefits for coastal tourism, recreation activities and coastal habitats preservation. In some cases, beach nourishment can use material extracted for another purpose, allowing it to be productively reused: in Anglet France , sediment dredged in the port of Bayonne to facilitate navigation is used for beach nourishment. Limiting factors: Beach nourishment potentially can negatively affect foreshore ecosystem with the burial of biota, the loss of habitats in nearshore sandbars, or the disruption of bird and other animal nesting, if it is not carried out properly.
Some species, such as sand-dwelling invertebrates, are sensitive to a change of sediment types. Studies show that the impact depends on the frequency of nourishment in a given area. Beach nourishment is usually an ongoing process, which leads to higher costs over time and repeated disturbance of the ecosystem. Nourishment does not end erosion; it only provides additional sediments on which erosion will continue.
Therefore, traditional small-scale onshore nourishment has to be repeated regularly because the sand stock is depleted either by coastal erosion or storm surges. Finding a source with sufficient quantities and good-quality sand can be challenging. The dredged sand should match the sand present on the site in terms of grain size, colour, and composition, unless it is a shoreface nourishment.
In Hel Peninsula Poland , the grain size of dredged sand from a nearby bay was much smaller than the grain size of sand taken in the open sea and was consequently easily dispersed, even in low energy wave currents. Consequently, erosion continued even though a large amount of sediment was spread over the beach. After research, sand from open sea sites and a nearby breakwater was preferred as more effective against erosion.
Beach Replenishment or Nourishment is a soft armoring technique that involves pumping sand onto an eroding shoreline to widen the existing beach. Virginia Beach has the oldest continuous fill program on the East Coast. Nourishment is a vital component of the Virginia Beach Hurricane Protection System, widening the beach to ft. Virginia Beach includes nourishment funding in the annual budget.
Mega-nourishment projects may require less maintenance and have ecological benefits compared to conventional replenishment. In one locality, widening the beach resulted in some properties moving from an A zone to an X zone, providing insurance savings to homeowners.
Programs are already established in many coastal localities. Expensive band-aid solution that requires re-nourishment periodically. Ecological concerns marine life and shorebird nesting may be impacted. Nourished beaches can erode x faster than natural beaches. Beach nourishment does not prevent erosion, and each project has a finite lifespan. The economic cost of nourishment projects is an important consideration.
Beach nourishment can serve as a natural SWM measure. For example, constructed dunes can reduce overland flow and promote infiltration from impervious surfaces abutting the beach. This is highly beneficial as it allows the widest range of coastal management options to be passed to the next generation.
Alongshore redistribution of the added material will occur through a process known as longshore drift, under the action of waves, tides and wind. Longshore drift is caused by waves approaching the shore obliquely, carrying beach sediments with them. When waves return to the sea however, the movement is always perpendicular to the shore.
This initiates a gradual alongshore movement of sediment as shown in Figure 3. As a result of sediment redistribution by longshore drift, beach nourishment is likely to positively impact adjacent areas which were not directly nourished.
This may provide wider benefits including reduced beach and cliff erosion for the entire coastal cell a coastal cell is a stretch of coastline within which sediment movement is self-contained.
Sediment within one coastal cell is not transported or shared with adjacent cells. Beach nourishment can complement hard protection measures such as seawalls, which may continue to be used as a last line of defence. The existence of a wide, sandy beach in front of such structures greatly reduces the wave energy reaching them, thus providing additional protection. Addition of sediment which closely resembles the native beach material will help retain the natural landscape of the beach, while providing an increased capacity for coping with coastal erosion and flooding.
The natural appearance of nourishment projects also means these schemes are aesthetically pleasing. As a result, beach nourishment has the potential to promote recreation and tourism through beach widening Nicholls et al. This may serve to enhance pre-existing tourism or may serve to attract tourists to the area, thus encouraging development. It is also possible to provide ecological benefits through beach nourishment. Schemes have been shown to provide enhanced nesting sites for sea turtles when designed with the requirements of these creatures in mind Dean, Today, nourishment is very popular in developed countries but has also found application in developing nations, such as Brazil Vera-Cruz, ; Elfrink et al.
The technology and methods involved are well established and many contractors experienced in beach nourishment are available worldwide to undertake such projects. As already stated, nourishment is not a permanent solution to shoreline erosion. This will require regular re-investment but can be viewed as a maintenance cost, such as those associated with hard engineered structures.
As with any type of shore protection works, reducing the risk of coastal flooding and erosion will result in an increased sense of security. To some extent, this is desirable. However, even in the presence of protective measures, the coastal zone remains susceptible to extreme coastal flooding and erosion events, and will remain exposed to natural disasters with long return periods. If not carefully regulated, protective measures may promote unwise development in these risky areas as a result of the increased sense of security.
Depositing sediments onto beaches can generate a number of negative environmental effects, including direct burial of animals and organisms residing on the beach, lethal or damaging doses of water turbidity — cloudiness caused by agitation of sediments — and altered sediment compositions which may affect the types of animals which inhabit the area Dean, As a result, projects must be designed with an understanding of, and concern for, the potential adverse consequences for the environment.
Special consideration should be given to the impacts upon important or rare species resident in the coastal zone. Placement of fill material on the beach can disrupt beach and ocean habitats, such as bird and sea turtle nesting, if schemes are not designed appropriately. The application of beach nourishment is expected to grow in the future and as a result, there may be higher demand for high quality sediment.
Limited availability of large contractors, coupled with an increase in demand for nourishment projects have already caused cost increases for nourishment projects in the Netherlands where it is widely applied Hillen et al.
This upward trend is likely to be observed elsewhere in future. Linham et al. The most important determinant of nourishment costs appears to be the transport distance for the beach material. Most of this data was collected in developed countries because this is where the vast bulk of nourishment occurs today. In developing countries, costs would, in general, be expected to be similar or possibly higher, due to their less developed coastal engineering industry.
Wide variation in costs is apparent between and within countries. Payment to contractors is usually based on the delivered volume of sediment. This normally requires surveys of the visible and underwater sections of the beach to be completed both pre- and post-nourishment. The ongoing cost of monitoring should be accounted for when considering the overall cost of nourishment.
Monitoring costs are likely to vary with local labour costs and, as such, could vary significantly between countries Mason, pers. Large-scale beach nourishments will typically require extensive engineering studies and specialised knowledge and equipment. This may include dredgers and pipelines that need to be hired from a specialised contractor.
However, it is also possible to conduct nourishment on a smaller scale. Beach-grade sediment can be transferred from land-based sources or from depositional to erosional areas by truck haul. Because of the smaller-scale nature of this approach and because readily available equipment could be used, nourishment by truck haul may be more practicable at a local level.
Once nourishment has been carried out, ongoing beach monitoring is needed in order to evaluate nourishment success and to determine when re-nourishment will be required. Nourishment schemes should be evaluated as a whole, however, which may require the participation of multiple communities if nourishment is undertaken on a large scale. Beach nourishment requires a suitable source of sediment to be identified in close enough proximity to the nourishment site.
This ensures that costs are kept at a reasonable level. Sediment availability is highly variable around the globe and suitable sources may not be easily found. The increasing popularity of beach nourishment worldwide may therefore cause sediment availability problems as demand increases.
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