Feb 24, 2024

How Water Responds to Land Reclamation in Coastal Cities

Land reclamation from the sea has become a popular phenomenon in coastal development. It is the most preferred solution to the need for land in coastal areas and has been implemented for various use cases, including flood control and agriculture. Nowadays, it has become a famous urban response to the rapid increase in coastal urbanization, economic activity, and global population. Countries like China and the Netherlands lead the chart on the amount of land area reclaimed. However, most reclamation projects today take place within urban centers in the global south. Cities in West Africa, East Asia, and the Middle East produce these new lands as economic forerunners for their commercial industry and as platforms to house luxury residences.

But the relationship between the design and production of reclaimed lands and the response of water in ocean environments is complex. It requires a symbiotic relationship with water bodies for stability but can provoke natural forces when negligently imposed on the sea. Ocean water behaviors, including tidal accumulation, sea level rise, connection to wetlands, and aquatic biodiversity, can question the success or failure of land reclamation projects in different contexts.

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Land reclamation has been practiced for centuries using various methods in different settings. Traditionally, cities employed dikes to enclose shallow waters and drain the enclosures to create dry land. An example of this is Zuiderzee in the Netherlands. In the 1900s, dams were built into the North Sea and the water was drained to create land for housing its growing population. In modern times, more concrete practices such as deep cement mixing directly in ocean environments and building sea walls to contain them have been implemented. The Sino-Singapore Tianjin Eco-city in China is a large-scale example of this modern practice, producing 6.2 miles of land for housing, industrial projects, and port facilities, boosting its urban growth and economy.

Coastal reclamation, despite its benefits to cities and the evolution of its methods, will inevitably impact the structure and behavior of ocean environments. Studies have shown that reclamation can alter the profile shape, bed slope, and sediment grain size of ocean environments, influencing local tide dynamics such as amplitude, asymmetry, and tidal currents. When natural ocean currents are obstructed, water finds its way by enhancing wave action and tides, naturally shifting in a new direction with extra force. This is the basis for water's response to land reclamation, and it determines the success, environmental impact, and sustainability of a land reclamation project.

For instance, Busan, South Korea's marine city, is a result of coastal reclamation. It has an urban shape that faces the sea on three sides and is home to luxurious residential high-rises. Built in the 1980s, the city is protected by a seawall on all sides. However, this project not only alters the shape of the coastline but also introduces hard land (concrete and asphalt) into the ocean, making the city more vulnerable to large storms and sea-level rise. In the last decade, the marine city has experienced a series of typhoons that caused waves to spill over the seawalls and flood its streets.

Another example is the Eko Atlantic City, Lagos, Nigeria. Interestingly, this reclamation project was conceived as an urban solution to protect the cultural capital from flooding, erosion, and rising sea levels. Through the dredging of nearby ocean floors, the soil was collected to reclaim 10.2km of land facing the Atlantic. It was bordered by an 8.2km seawall and planned to accommodate highrise housing projects which will sustain the city’s growing population. However, this land reclamation project also had negative environmental implications. It eliminated the wetlands, which previously served as a buffer between coastal areas and the ocean, and changed the water flows to surrounding areas, leading to greater erosion in those parts of the city. Additionally, the coastal areas where the ocean floors were dredged are currently vulnerable to storm surges and have experienced successive flooding over the years. These examples demonstrate that a lack of sensitivity to water behavior and inadequate design of land reclamation projects can have long-term negative effects on the environment.

In a positive light, the land reclamation scheme of Shanghai, China, is one that notes existing coastal conditions and responds to water behavior. Through reclamation techniques of building seawalls and dredging, the city has added well over 580 square kilometers (220 square miles) of land to its shorelines since 1985. Although most of the added lands were intended for ports, industry, and housing to fuel the city's growth, a significant portion was also designated for parks, forests, inland lakes, and wetlands. The urban design was carefully planned to consider the ocean water's response to built obstructions and the role of wetlands as a buffer between the ocean and the land, which helps absorb much of the ocean's force. Despite being identified as a city vulnerable to flooding and future climate change, Shanghai has employed sensitive land reclamation practices to mitigate the ocean's impact.

It is evident through these various reclamation examples, coastal factors such as the wetlands, the shape of the coastline, the structure of the ocean bed, and local tide dynamics all contribute to the sustainability of land reclamation projects. Eliminating natural flooding erosion systems of wetlands can lead to more flooding, and preventing flooding in one location can cause water to find a new direction, which can lead to flooding in other locations. Wetlands are not only buffers for flooding and erosion but also habitats for unique aquatic species. They are marine ecology zones that house coral reefs, horseshoe crabs, seaweed beds, and other species near the coast. These organisms have a major impact on the ocean’s food chain and control its overall biodiversity. Destroying them can lead to long-term ecological disasters. So, we have an environmental responsibility to sustain them and cannot eliminate their habitats to suit land reclamation projects.

The discourse surrounding ocean water's response to the design and reclamation of lands in coastal areas has expanded. In addition to paying attention to the tidal dynamics of water, we should view these areas as homes to vast ecological species. All aspects of land reclamation projects, from decision-making and location in the oceans to coastline design, marine ecology conservation, ocean structure, local tides, and wetlands, must be examined sensitively to promote a sustainable coastal environment.

This article is part of the ArchDaily Topics: Water in Architecture, proudly presented by Hansgrohe.

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Paul YakubuThis article is part of the ArchDaily Topics: Water in Architecture,