Beach nourishment describes a measure where sediment that is lost due to longshore drift or erosion on a beach is replaced from material outside of the eroding beach. This results in a wider beach that can reduce storm damages and coastal erosion. Beach nourishment is typically a repetitive measure, since it does not remove the physical forces causing erosion, but is a measure that mitigates the effects of erosion.
Beach nourishment is the mechanical re-placement of sand in the coastal zone to maintain sand in the littoral system. It stabilizes the shoreline and supports the flood and/or erosion protection of the coast. Beach nourishment has been widely practised in Europe in the last decades. For example the first beach nourishment carried out in Germany took place in 1951, in Italy in 1969, and in the Netherlands in 1970 (see H. Hanson et al. 2002). Beach nourishment is sometimes also called beach recharge.
Instead of using hard constructions to hold the shoreline, the concept of beach nourishment is based on the concept of ‘working with nature’. This is an approach where natural dynamics are being used with less impact to the environment. It may also increase the recreational value of the coastal zone.
The sustainability of this approach depends heavily on the nourishment material. It should fit to the composition of the original beach material (mainly grain size) and the local process and beach movements. Mostly the material is dredged from sea-beds, but also alternatives are possible; for example dredged material from ports or streams. This material must be carefully sampled to ensure the material is of right composition and is not contaminated in any way.
Also the position of the nourishment will have an effect of the sustainability of the measure. Possible locations include the upper beach and dune face, the mid to lower beach and the shallow nearshore zone. Nourishments on the upper beach and dune will have an immediate benefit, but it can be rapidly redistributed alongshore or across the beach by waves and currents to form a new equilibrium profile. Placement of sand on the mid-beach anticipates this redistribution, and provides shoreline protection by helping to dissipate wave energy before it reaches the dunes. Placement below the water line also anticipates the redistribution and allows sand to be fed into the beach system gradually. This latter approach is only appropriate to very large recharge schemes. This implies that nourishment should only be undertaken where there is a good knowledge of the local beach processes and movements.
Political & social feasibility
Between European countries there are significant differences in the organization of beach nourishments. Schasfoort and Janssen (2013) state that the Netherlands and Denmark have an overall performance evaluation program integrated into their legal framework. They and also Germany and the UK have developed a long-term strategy for actions along the coast and following up programs, while Spain, Italy and France lack an overall long-term strategy.
With the different frameworks for the different EU countries, the governance of beach nourishments is highly dependent on the country of execution and also on the specific location.
However, aligning the interest of authorities, stakeholders and the public is critical since these actors have different interest in the affected area of the nourishment. Since this measure will also have an impact on coastal zones adjunct to the executed nourishment, the involvement of stakeholders from these areas isare also necessary. These involvements should address topics like responsibilities, budget rules, and public information campaigns (Link to measure: „public information“).
Especially for the public, there are several issues that have to be addressed (based on Scottish Natural Heritage, 2000):
- develop a public access routes to the beach. It should be clearly laid out and fenced where necessary to prevent trampling that may lead to blowouts.
- Educational displays at backshore car parking areas or along footpaths should be used to explain management schemes and encourage public interest and support for the management objectives.
- Warning signs should be set up highlighting the dangers of unstable dune faces, any construction work in progress or any other hazards associated with the management schemes (gaps in rock structures, slippery algal growth, buried defences, submerged structures, mud deposits, etc).
Cost of implementation & maintenance
The costs for this measure depend on the source, transport, and volume of material needed, expected life-time of measure (intervals of repetition), if necessary additional secondary measures (like groynes, breakwaters, plantings on dunes, etc.) are needed. Also the place of the nourishment has an influence of the price of the measure. Beach and dune nourishments are considerably more expensive than shore face nourishments, due to the use of bulldozers to spread the sand and indirect costs of disrupting beach tourism (Schasfoort and Janssen 2013). One very distinctive element is the restricted lifetime and the requirement of regular investments. Therefore one single execution may not be too expensive but over the years the measure cumulates some costs.
Beach nourishments can create additional benefits. It can have indirect positive effects for local tourism or increase the value of the land near the sea. But these benefits hard very difficult to monetize (see Hartje et al. 2001; Schasfoort and Janssen 2013)
In general, beach nourishment is seen as an environment friendly option for coastal protection and beach restoration. Especially in comparison with hard coastal defence measures like groynes or dikes it allows a semi-natural process of the beach development. But a literature review by Speybroeck et al. (2003) shows that sizable impacts on several beach ecosystem components (microphytobenthos, vascular plants, terrestrial arthropods, marine zoobenthos and avifauna) were observed in executed nourishments. The highly dynamic nature of the littoral zone mainly determined by waves, tides, and winds leads to an ecosystem that is adapted to several forms of environmental stress. Therefore, nourishment should only cause minor damages to the ecosystem but the tolerance is not unlimited. Nourishments bring sizable changes in the sandy beach ecosystem of the resident flora and fauna is destroyed by the addition of a thick layer of sand. It will also have an effect on the beach profile and sedimentology, which will affect the biocoenosis (see Speybroeck et al. 2003). Also, the sand mining for the nourishment cause a disruption of habitats, transitory fishes and marine mammals at the place of extraction (Schasfoort and Janssen 2013).
Speybroeck et al. (2003) list possible impacts and ways to reduce these impacts. Negative effects are based on different factors:
- activities during construction phase,
- quality and quantity of the nourished sediment,
- timing, place and size of project,
- the nourishment technique and strategy applied,
- and the physical environment prior to nourishment.
There are several ways to limit the negative impact on the environment:
- use nourishment sands with a sediment composition comparable to that of the natural sediment
- avoid short term compaction by ploughing immediately after construction,
- execute the nourishment in a period of low beach use by birds and other mobile organisms
- choose a number of smaller projects rather than a single large nourishment project
Nowadays beach nourishment is a common approach in Europe to stabilize the beach and hinder the effects of erosion. Even though it is not eliminating the cause of erosion and is a reiterate approach, it is widely accepted because it has a relatively low impact on the ecological system and leaves the beach in a condition that serves tourism.