Beach nourishment, also called beach renourishment, beach replenishment, or sand replenishment, is a method used to replace sand that has been lost due to erosion or the movement of sand along the shore. Adding more sand to the beach can help protect buildings and other structures near the coast. A wider beach spreads out the force of waves and storm surges, reducing damage from storms, tsunamis, and high tides. Beach nourishment is usually part of a larger plan to protect coastal areas. This process often needs to be repeated because it does not stop the forces that cause erosion; it only helps reduce their effects.

The first beach nourishment project in the United States took place at Coney Island, New York, in 1922 and 1923. Today, this method is widely used by both public and private groups to protect shorelines.

History

The first nourishment project in the United States was built at Coney Island, New York, between 1922 and 1923.

Before the 1970s, nourishment involved putting sand directly on the beach and dunes. Since then, more shoreface nourishments have been done, which use the power of wind, waves, and tides to spread the sand along the shore and onto the beaches and dunes.

The number and size of nourishment projects have grown a lot because of population growth and the expected rise in sea levels.

Erosion

Beach erosion is a type of coastal erosion, which is a form of erosion caused by living things that changes the shape of coastlines through the movement of sand and other materials. Many beaches are shrinking today, often because of changes in the way sand moves along the shore and because of human activities that harm the coast.

Beaches can lose sand naturally or because of human actions, such as removing sand for construction or mining.

Erosion happens naturally during storms. When storms occur, sand from the visible part of the beach moves underwater to form sand bars that help protect the beach. This movement is only one part of the process. During calm weather, smaller waves bring sand back from the bars to the visible beach in a process called accretion.

Some beaches do not have enough sand to naturally recover from storms. Without enough sand, the beach cannot rebuild itself after a storm.

Many areas with severe erosion are caused by human activities. These include seawalls that trap sand dunes, buildings like ports and harbors that stop sand from moving along the coast, and dams or other river structures. Long-term efforts to add sand to beaches, especially in certain coastal areas, can stop the natural movement of sand and cause erosion farther down the shore. These activities prevent sand from moving naturally by building dams (which reduce sand from rivers), creating barriers like jetties, or deepening waterways.

Types of shoreline protection approaches

Coastal engineering for shoreline protection includes the following methods:

• Soft engineering: Beach nourishment is a gentle method that helps protect beaches by adding sand to create a larger sand area. This pushes the shoreline outward and avoids using permanent structures.
• Hard engineering: Hard structures are used to manage beach changes. Four common types include seawalls, revetments, groynes, and breakwaters. Seawalls and headland breakwaters (breakwaters connected to the shore using groynes) are the most frequently used.
• Managed retreat: This method allows the shoreline to erode naturally. Buildings and other structures are moved inland to avoid damage from erosion.

Approach

Beach nourishment involves adding sand to beaches. This process helps widen beaches, protects buildings behind them, and shields areas from storm damage. It can increase the value of nearby land, boost the economy through tourism and recreation, and create more space for animals to live. It is a practical and environmentally friendly way to reduce erosion. Adding sand also encourages plant growth, which helps stabilize tidal areas.

However, there are challenges. The added sand may be lost during storms or if there is not enough sand from nearby areas. The process is costly and often needs to be repeated. During nourishment, access to certain areas may be limited. It can harm or cover marine life, and finding the right type of sand can be difficult.

Nourishment is usually a repeated process because it reduces erosion effects but does not eliminate the causes of erosion. In areas with less erosion, nourishment projects happen less often, which lowers costs. In places with high erosion, nourishment may become too expensive to be practical.

In many coastal regions, wide beaches have significant economic benefits. Since 1923, the United States has spent $9 billion to rebuild beaches. A famous example is Miami Beach, Florida, where 10 miles of shoreline were restored between 1976 and 1981. The project cost about $86 million and helped improve the local economy. Before nourishment, some beaches were too narrow to walk on during high tide.

In 1998, a study found that 418 beach nourishment projects had been completed in the United States. These projects involved 648 million cubic yards of sand, costing about $3.4 billion (adjusted to 1996 prices). The cost was about $6.84 per cubic meter. Between 2000 and 2020, prices in the United States increased, while in Europe, prices decreased.

In areas near the North Sea, nourishment is often less expensive. In 2000, the North Sea Coastal Management Group collected data on nourishment projects. In the Netherlands, detailed information about nourishment projects is available. In areas without nearby sand-dredging equipment, nourishment costs are typically between €20 and €30 per cubic meter.

A wide beach can absorb energy from storms, which is important in low-lying areas where storms might damage buildings. Studies after storms and coastal engineering principles show that wide beaches reduce damage to structures.

Beach nourishment can affect local ecosystems. Adding sand may bury some sea creatures that are attached to the seafloor. It can disrupt habitats in both the source and target areas, such as when sand is placed on coral reefs or hardens. Imported sand may have different chemical or grain characteristics than local sand, which can affect light availability for reefs and plants. Imported sand might also contain harmful materials. Removing sand from near-shore areas can destabilize shorelines by changing underwater slopes. Efforts to reduce erosion may give a false sense of security, leading to more development.

Newly added sand can harden, making it harder for turtles to dig nests. However, nourishment can also create better habitats for turtles, seabirds, and beach plants. In Florida, special grills were added to dredge pipes to prevent turtles from being sucked into pumps.

Choosing the right material for a project depends on design needs, environmental factors, and transport costs. The most important factor is the size of the sand grains, which should closely match the natural sand. If the sand has too much silt or clay, it may not be suitable. Projects with mismatched grain sizes often perform poorly. Using slightly smaller sand than natural sand can lead to narrower beaches over time. Evaluating materials usually involves surveys with geophysical data and samples.

Some beaches were nourished with finer sand than the original. Studies show that such beaches erode faster during storms, as seen in a project in Waikiki, Hawaii.

Beach profile nourishment refers to programs that add sand to the entire beach profile, including the underwater slope. In some areas, more sand is added below the waterline to allow the beach to grow naturally over time. These methods do not permanently stop erosion caused by human activity, which must be addressed separately.

Nourishment projects aim to achieve physical, environmental, and economic goals. Physical measures include the width and height of the dry beach, sand volume after storms, and damage prevention. Environmental measures track marine life, habitats, and species counts. Economic impacts include tourism, flood prevention, and disaster risk reduction.

Some projects are supported by studies showing increased tourist spending. However, these studies may not account for all costs or benefits. Methods to include nourishment in flood insurance and disaster aid remain debated.

Beach nourishment works best on long, straight shorelines without inlets or man-made structures. Predicting overall beach changes is more reliable than predicting changes in specific areas.

Nourishment can affect eligibility for the U.S. National Flood Insurance Program and federal disaster assistance. It may also unintentionally encourage more coastal development, increasing risks from other coastal hazards.

Other shoreline protection approaches

Nourishment is not the only method used to stop beach erosion. Other methods can be used alone or with nourishment, depending on economic, environmental, and political factors.

Human activities, such as building dams, can stop natural sand movement, reducing the amount of sand that reaches the beach. Building barriers like jetties or deepening inlets can also stop sand from moving along the shore.

The structural method tries to stop erosion by building strong barriers. These include seawalls, revetments, and breakwaters. Structures that run parallel to the shore, like seawalls, protect buildings but do not help the beach outside the wall. Over time, the beach may disappear completely.

Structures that run perpendicular to the shore, like groynes and breakwaters, can protect the beach from erosion. Filling breakwaters with sand can help prevent them from trapping sand, which might otherwise cause erosion in other areas.

Structural methods can block access to the beach, make nearby areas erode faster, and need regular repairs.

Managed retreat involves moving buildings and other structures inland as the beach erodes. This is often used in places where erosion is fast or where there are few or outdated buildings.

Beaches change size based on tides, rain, wind, waves, and ocean currents. Wet beaches lose sand more easily. Waves deposit sand on dry beaches. Beaches are usually wet during falling tides because the sea level drops faster than the beach can drain. This often causes erosion. Using special tubes called Pressure Equalizing Modules (PEMs) can help the beach drain faster during falling tides. These tubes are placed vertically in the sand and connect layers of groundwater. Water flows through the tubes into coarser sand layers, where it drains more quickly. PEMs are arranged in rows from the dune to the low tide line, spaced about 300 feet apart, depending on the project. PEM systems vary in size and connect layers with different water flow abilities. Air and water can enter the tubes to balance pressure.

PEMs are minimally disruptive, covering about 0.00005% of the beach. The tubes are hidden underground and not visible. PEMs have been used on beaches in Denmark, Sweden, Malaysia, and Florida. However, their effectiveness in stopping erosion on large sand beaches has not been proven clearly. While PEMs lower the water table, other natural forces often outweigh their benefits for fine sand. Some studies show mixed results, with sand building up in certain areas but erosion continuing elsewhere. This matches what scientists know about how water and sand interact on beaches.

Fences built correctly can trap wind-blown sand, helping rebuild dunes and protect the beach from wind and sand loss.

Another method is creating a dynamic revetment, which is a flat area made of loose, mixed rocks. Seeds placed among the rocks can grow and hold the rocks in place. Sand can collect around the rocks, forming a beach again. Allowing the rocks to move helps them settle in stable spots. A second flat area near the highest water level can speed up recovery. This method was used at Washaway Beach in North Cove, Washington. Within one year, the beach grew by about 15 meters and continued to expand. Similar techniques have been used in Washington, California, Europe, and Guam.

Projects

The location of a beach nourishment project is important for its design and how well it works. Possible locations include a long, straight beach, an inlet that may be natural or man-made, or a pocket beach. Rocky or seawalled shorelines that have no sand create special challenges.

In 2005, Hurricane Wilma damaged the beaches of Cancun and the Riviera Maya. The first beach restoration project cost $19 million but failed. A second project started in September 2009 and was expected to finish by early 2010 at a cost of $70 million. Engineers and the government agreed to continue maintaining the beaches to prevent future erosion. They considered factors like the season and sand qualities, such as how tightly packed the sand was. The restoration in Cancun aimed to add 1.3 billion US gallons (4,900,000 m³) of sand to cover 450 meters (1,480 ft) of coastline.

Gold Coast beaches in Queensland, Australia, have faced serious erosion. In 1967, a series of 11 cyclones removed most of the sand from these beaches. The government of Queensland asked engineers from Delft University in the Netherlands for help. The 1971 Delft Report suggested solutions, including beach nourishment and building an artificial reef. By 2005, most of these suggestions had been carried out.

The Northern Gold Coast Beach Protection Strategy (NGCBPS) cost A$10 million. It was completed between 1992 and 2003. The project involved moving 3,500,000 cubic meters (4,600,000 cubic yards) of sand from the Gold Coast Broadwater to nourish 5 kilometers (3.1 miles) of beach between Surfers Paradise and Main Beach. The sand was kept in place by an artificial reef made of large geotextile sand bags near Narrowneck. This reef was designed to improve wave conditions for surfing. A key part of the project was the ARGUS coastal camera system, used to monitor the beach.

More than one-quarter of the Netherlands lies below sea level. The coastline along the North Sea (about 300 kilometers or 190 miles) is protected from flooding by natural sand dunes, except in estuaries and behind barrier islands. This coastline has been eroding for centuries. In the 19th and early 20th centuries, people tried to stop erosion by building groynes, but this was expensive and not very effective. Beach nourishment worked better, but there were questions about how to fund it. In 1990, the Dutch government decided, after a detailed study, that all erosion along the entire coastline would be fixed using artificial beach nourishment.

The shoreline is monitored yearly by measuring cross sections of the beach at points 250 meters (820 feet) apart to ensure proper protection. If long-term erosion is found, beach nourishment using high-capacity suction dredgers is used. In 1990, the Dutch government decided to use nourishment to fix all coastal erosion. This policy continues today and has been successful. All costs are covered by the National Budget.

A new beach nourishment strategy was used in South Holland. A new beach shape was created using large amounts of sand, with the hope that natural processes would spread the sand to nourish the beach over many years (see "Sand Engine").

The basic coastline in the Netherlands represents the low water line from 1990. This line helps identify erosion and growth along the coast and determines if action is needed. In the Coastal Memorandum of 1990, the government decided to keep the 1990 coastline by using beach nourishment. The coastline in question is the low-water line. For practical use, the memorandum also defines the momentary coastline (MKL) and the basic coastline (BKL). Each year, the shoreline to be tested (TKL) is determined based on the MKL. If the shoreline threatens to move inland from the BKL, sand nourishment is done.

A problem with the low water line mentioned in the 1990 Coastal Memorandum is that the average low tide height is clearly defined, but its position horizontally is not. The beach profile crosses the low water line three times. It is not important to maintain a line, but to keep the amount of sand in the active beach profile. To measure this volume, two heights are used: the average low water level (glw) and the height of the dune foot (dv). The dune foot is determined by finding where the steep slope of the dune meets the dry beach. This point is usually slightly below the sand. It is hard to redefine the dune foot height every year. Some administrators define the dune foot line as a certain elevation, where the dune foot usually lies. In areas where the coast is stable, this is acceptable. The method for determining the MKL is not very sensitive to the exact value of dv. The location of the dune foot is determined by its height above NAP (National Datum, roughly mean sea level) and the distance from that elevation line to the administrative coastline (Xdv). This administrative line has no physical meaning but is used for survey work.

The steps to calculate the position of the MKL are:

• Find the location of the dune foot.
• Determine the height of the average low water (glw).
• Calculate the height h of the dune foot above average low water.
• Calculate the sand volume A, which is the amount of sand seaward of the dune foot and above the level (glw – h).
• Define the position of the momentary coastline (SKL) in relation to the national beach pile line as: (A/2h) – Xdv.

This method assumes that the thickness of the sand layer depends on wave height, but this is unknown. However, since the elevation of the dune foot also depends on wave height, the value h represents the combined effects of tides and waves. For measuring beach profiles, so-called JarKus profiles are used. These profiles are spaced about 250 meters apart and are measured annually from around 800 meters offshore to just behind the dunes. These measurements have been available along the coast since 1965. From around 1850, some profile soundings are also available, but they are often slightly shifted compared to the JarKus measurements, making them harder to analyze. In areas with groynes, soundings are taken exactly in the middle between the groynes.

The Basic Coastline (BKL) is defined as the coastline on January 1, 1990. However, there are no exact measurements from that date, and measurements always vary slightly. The B