5.7: Human Impacts on Beaches

The longshore and cross-shore transport of sand from rivers and the journey of sand from the mountains to the sea are eloquently documented in an Encyclopædia Britannica video classic, The Beach: A River of Sand (1966). The film—now more than 50 years old—also tells another story, a darker story, one that reveals the ways people have altered the natural functioning of beaches.

Beaches serve as the centerpiece of a trillion-dollar global tourist ocean economy (Brumbaugh and Patil 2017). In the US alone, beaches generate billions of dollars in revenue from tourists and beachgoers (e.g., Houston 2018). Municipalities in charge of maintaining beaches have a strong desire to make sure that the sand on the beach stays clean and stays put—no sand, no tourists, the thinking goes.

Human activities can disrupt the natural flows of sand. In some cases, these activities lead to increases in the amount of sediments flowing downstream. In others, the supply of sand is diminished. Both have consequences for the coastal ecosystem and for human wealth, health, and safety.

State of the World’s Beaches

Using observations from satellites, researchers can now reasonably estimate the state of the world’s beaches and their changes over time. A recent study found that about a quarter of the world’s beaches are eroding, about a quarter are growing, and about half appear stable (Luijendijk et al. 2018). Whether that’s good news or bad news depends on where the beaches are located.

More than two billion people and a third of the world’s “megacities” live in the coastal zone, defined as the area within 62 miles (100 km) of a coastline (Small and Nichols 2003). Compiling a global database on beaches using data from remote sensing platforms, researchers can identify “hotspots” where beaches are either losing sand or gaining sand (Luijendijk et al. 2018). Four of seven receding hotspots are in the United States. The world’s fastest-growing beach is in southwest Namibia, where an active beach diamond mining operation adds sand to the beach.

Too Much Sand?

Several human activities increase the downstream flow of sand to beaches. Mining, deforestation, agriculture, and road construction rank highest on the list. These activities result in an oversupply of sediments that clog urban and coastal waterways, generate dangerous debris flows, and damage coastal ecosystems.

An overabundance of sediments has several negative consequences. Sediments can bury organisms, deliver toxins, reduce light penetration required for the growth of marine seaweeds and plants, and promote the growth of harmful bacteria (e.g., Granger et al. 2010; Mekonnen et al. 2015; Saunders et al. 2017; Lintern et al. 2018). However, these negative consequences can be reduced by restoring natural flows of sediments.

Too Little Sand?

Manmade structures can block the natural flow of sand. Paving of land (reducing erosion), construction of dams, and building of coastal infrastructure to trap sediments upstream (e.g., groins, jetties, and seawalls) may impede the flow of sediments to a beach. Anything that reduces the natural weathering processes or that alters the downstream transport of sediments will reduce the delivery of sediments to the ocean.

Beaches whose supply of sediments is shrinking experience beach starvation. In California, a study by the US Geological Survey revealed that 40 percent of beaches have experienced long-term erosion—over 120 years—and 66 percent exhibited severe short-term erosion—over 25 years (Hapke et al. 2009).

Starved beaches are more susceptible to extreme waves and more prone to flooding as a result of sea level rise, especially during times of king tides. When water moves closer to shore, coastal structures suffer damage by waves and intrusion of saltwater, which dissolves metals and corrodes machinery. People can no longer enjoy the beach because much of it is gone. Fewer beachgoers translates into economic losses for industries dependent on coastal tourism. Beach erosion can be deadly as well. In 2019, three people lost their lives when a coastal bluff collapsed at Grandview Surf Beach in Encinitas, California (Xia 2019).

One cause of beach starvation is the damming of rivers. Used for flood control or to generate power, dams prevent the flow of sand to the beach. The sand becomes trapped behind the dam. Starved of its natural supply of sediments, the beach shrinks. In recent years, dam removal has been carried out to restore coastal sediments. The largest project ever attempted—removal of two dams on the Elwha River in the state of Washington—resulted in a release of 30 million tons of sediments into the watershed (Ritchie et al. 2018). Remarkably, after nearly a hundred years of beach and estuarine sediment starvation, a supply of sand was returned to the shoreline (Warrick et al. 2019).

Other impediments along coastlines are structures built along shorelines. Groins, concrete and rock structures built perpendicular to the shore, act as a barrier to maintain sand on beaches. While groins effectively trap sand on their upstream side, they cause a deficit of sand on their downstream side. Coastal armoring—paving or hardening of bluffs and seawalls to block wave action—protect shorelines, at least temporarily. However, armoring reduces bluff erosion, cutting off a source of sand. Seawalls intensify wave energy and increase erosion adjacent to the seawall. The net effect of these efforts is to reduce flows of sand and disrupt natural beach processes (e.g., Pilkey and Cooper 2012).

Beach Nourishment

Another temporary measure is the feeding of beaches. Beach nourishment refers to the practice of adding sand directly to the beach from an external source. Sand may be dredged from channels or river mouths and piped to beaches or transported from local deserts. Whatever the source, beach nourishment can be costly and may have negative consequences for coastal ecosystems (e.g., Speybroeck et al. 2006; Elko et al., 2021). Like the giant man-eating plant in the film Little Shop of Horrors (Corman 1960), some beaches just can’t be fed enough.

To track beach nourishment efforts, the Program for the Study of Developed Shorelines at Western Carolina University in North Carolina maintains a public website (beachnourishment.wcu.edu). According to its database, more than 350 million cubic yards of sediment have been applied to 343 sites in California at a cost exceeding $281 million (2019 dollars).

Orange County, California, recently completed a $19.5 million sand management project—dredging the Santa Ana River mouth and using the dredged material to replenish local beaches (Connelly 2016). Despite these efforts, beach nourishment in California has met only about half of the sand deficit (Patsch and Griggs 2007). Long-term beach erosion and cliff retreat remain problems on at least 40 percent of California beaches (Hapke et al. 2009).

In New Jersey, nearly a billion dollars has been spent on beach nourishment in the past three decades. The choice is one to maintain the beach (through nourishment) or rebuild coastal homes every decade or two. As one coastal manager justifies it, “We live on the shore. We love the beach. We need to maintain it. . . . Yes, it’s expensive, but it’s not the most expensive thing you can do for shore protection” (O’Neill 2015).

Sand Mining

Journalist and Los Angelino Vince Beiser calls sand “the most important solid substance on Earth.” You might think he’s joking until you realize that sand is part of just about everything we build. As marvelously portrayed in Beiser’s book, The World in a Grain: The Story of Sand and How It Transformed Civilization (2018), the world is running out of sand.

It turns out that sand is an essential ingredient of concrete, the stuff of which modern civilization is built. The other two ingredients are cement and gravel, but these are abundant. And though sand is also abundant, it turns out that only a special kind of sand works to make concrete. That sand is largely found on beaches. Desert sand has grains that are too smooth. Smooth grains in a concrete make it fall apart. Beach sand, on the other hand, has angular grains that lock together in the matrix of the cement. In essence, beach sand makes concrete hard. And the bulk of sand goes into construction. To build using concrete, you need sand. Lots and lots and lots of sand.

Sand can only be obtained by mining it—sand mining—shoveling sand off beaches or sucking it off the seafloor. Not surprisingly, sand mining operations can be found on beaches and coastal waters all around the world. Unfortunately, sand mining operations often destroy the habitats where the sand is extracted. As you might guess, mining of sand from beaches accelerates beach erosion. It can also negatively impact sensitive nearshore habitats, such as coral reefs, mangrove forests, and seagrass beds (Beiser 2018). Environmental concerns led the state of California to shut down one of the longest-operating sand mining operations in the United States, the CEMEX Sand Mine in Marina, California (very near Cal State University, Monterey Bay). The plant, blamed for accelerating beach erosion, ended operations in December 2020 (Shalev 2020).

As sources for sand dwindle, people turn to illegal means to obtain it. Beiser describes what he calls the “sand mafia.” In parts of India, where the illegal sand economy is estimated at $2.3 billion annually, local residents describe torture and murder in the name of sand (Beiser 2018). Stealing and smuggling have become so prevalent that some countries have now banned exports of sand.

Experts believe that the only way to reduce environmental threats and violence is to implement some kind of “global sand governance system” (Torres et al. 2017). Better data on the global demand for sand will enable development of a global sand budget. And efforts must be taken to raise public awareness of the “sand crisis” to spur policymakers to take action. Regulations with sensitivity to local concerns and means for enforcement and monitoring will enable “the global community . . . to use sand more sustainably and avert a tragedy of the sand commons” (Torres et al. 2017).

Beach Diamond Mining

Though limited to one region of the world, beach diamond mining in southern Namibia, near South Africa, deserves mention. Diamond mining developed in 1908 when Zacharias Lewala, a Namibian railway worker who had worked previously in a diamond mine, recognized on the ground several kimberlite rocks, the kind of deep mantle rocks that contain diamonds. He showed them to his German boss, August Stauch (1878–1947), who staked a claim on the area and became a millionaire. For his part, Lewala’s name earned a place in the history books, but little else is known about the man (e.g., Badenhorst 2003).

Similar to alluvial mining, beach miners sift the sand for rock and diamonds, often using heavy machinery and giant sifters. Front loaders and shovels may be used where diamond-bearing material occurs. To gather the diamonds, workers use brooms and hand collection. Conditions for workers appear less harsh than in “blood diamond” regions, primarily because of strong agreements between the sole mining company, De Beers, and the Namibian government (Munier 2016). But the mines are nearing the end of their profitability—less than 15 years may remain—so alternative employment (including cutting and polishing of diamonds) and other possible industries (such as tourism) are being considered to offset unemployment as the diamonds dwindle.

Living Shorelines

Ultimately, best practices for protecting coastal habitats from upstream threats involves ecosystem-based management principles, which encompass the full range of interconnections between ocean, estuarine, wetland, freshwater, and land habitats. Sheaves (2009) refers to the connectivity between land and sea as “the coastal ecosystem mosaic.”

One recent approach involves a kind of hybrid between constructed and natural landscapes. Known as living shorelines, this approach combines structural materials (natural and artificial) with natural vegetation and marine organisms to protect coastlines and preserve the ecological services that coastal habitats provide (e.g., Sutton-Grier et al. 2015).

As the concept of living shorelines has matured and gained acceptance, coastal stakeholders have increasingly turned to its principles to ensure success of their projects (e.g., Bilkovic et al. 2017). Structures that reduce erosion upstream prevent those materials from moving downstream. Installation of permeable surfaces traps sediments and debris in place. Biological filters help remove nutrients and toxins and other harmful substances. While solutions based on incorporating natural processes into urban systems remain relatively new, their potential to solve a wide variety of environmental threats makes them promising, if not essential.