Coastal management

Coastal management refers to the strategies used to defend against flooding and erosion. It also includes techniques used to claim new lands by stopping erosion. These efforts are increasingly vital because sea levels are rising due to climate change. As sea levels accelerate, tidal energy can disturb coastal sediments. Coastal zones are small, occupying less than 15% of the Earth's land area. However, they are incredibly crowded, hosting more than 40% of the global population. Nearly 1.2 billion people live near a coastline. This population density is three times higher than the global average. By 2025, it is expected that three-quarters of the world's population will live in these coastal zones.

Human history is closely tied to the engineering of coasts. Coastal engineering for harbors likely began before 3500 B.C. with the rise of maritime traffic. The Romans introduced many major innovations in harbor design. They were able to build walls underwater and construct solid breakwaters. To do this, they used a special material called Roman concrete. They also used rubble mounds and arched breakwaters built with timber floating caissons. In the Netherlands, the Romans were the first to use dredgers to maintain the harbor at Velsen. While many Roman structures disappeared after the fall of the Western Roman Empire, some submerged remains are still visible today.

In the Middle Ages, many coastal towns were abandoned due to attacks from the sea. Some harbors were also lost to natural causes like rapid silting or shifting shorelines. The Venetian Lagoon is a unique historical example of continuous prosperity. It provides some of the earliest written reports regarding the use of sea walls to protect settlements. After the Renaissance, there was little improvement in harbor construction until the early 19th century. The advent of the steam engine and the expansion of the British Empire helped revitalize sea trade. This renewed interest led to a massive increase in port works and coastal engineering projects.

Modern coastal management has shifted from "hard" to "soft" engineering. Before the 1950s, the standard practice was to use hard structures. These included seawalls, revetments, and groynes to protect against storm damage. During the 1920s and 1930s, local communities often built these structures on an ad hoc basis. However, these hard structures sometimes caused the loss of beach areas and impeded recreation. In the late 1940s, engineers began a more dynamic approach. They started using artificial beaches and stabilized dunes to replicate natural systems. These soft engineering methods are often more economically viable and environmentally friendly.

There are five general strategies used for coastal defense. The first is managed retreat, which allows an area to erode. This is often used when land is of low value or when sea levels rise. For example, in 1991, a small area at Northey Island in the UK was flooded through managed retreat. The second strategy is armoring, which involves building hard structures like seawalls. The third strategy is to construct defenses seaward of the coast. The fourth is adapting vertically by elevating land and buildings. Finally, limited intervention allows natural processes to take place in areas of low economic importance.

One common hard engineering method is the use of groynes. A groyne is a wall built perpendicular to the coastline. It is designed to trap the sedimentation caused by longshore drift. This process creates a wider beach that absorbs wave energy. Groynes can be made of concrete, rock, wood, or greenharts. While they are cost-effective, they can cause "terminal groyne syndrome." This happens when a groyne prevents sediment from reaching other nearby areas. This has been observed along the Hampshire and Sussex coasts in the UK.

Coastal management must also account for the danger of "coastal squeeze." This occurs when sea levels rise and ecological zones try to move landward. If they encounter solid human structures, they have nowhere to go. This makes wetlands, salt marshes, and mangroves particularly vulnerable. To manage this, the European Council issued the European Code of Conduct for Coastal Zones in 1999. This document helps guide national legislation and promotes integrated management. Effective planning is necessary to balance the needs of growing populations with the protection of fragile coastal ecosystems.