Back on April 9th I wrote about some of the unique planning issues that arise for cities built on an isthmus. In a subject near and dear to the hearts of Michiganders, today’s post identifies and discusses those urban areas that have developed along narrow straits (or a “detroit” in French) separating two land masses. In physical geography and navigation, straits may be also called channels, narrows, and passages. A strait is essentially the exact opposite of an isthmus.

The post does not include those cities that are situated on a very wide strait or channel, such as the Florida Straits or the Taiwan Straits, since the majority of the planning issues and impacts cited below would not be the same. Below is a list of some of the key urban areas that have grown along one or both sides of a channel, narrow, or strait. A weblink to a satellite map of each is also provided.

Among the planning considerations uniquely related to urban areas sited along narrow straits are:

These urban centers are often key international trading and shipping points. Singapore may be the best example of a global shipping center – this city-state has one of the world’s busiest harbors. From ground transport perspective, the Ambassador Bridge alone between Detroit and Windsor is busier than any other international crossing in North America.

In a number of cases the narrow or strait is also an international border crossing – by bridge, tunnel, or ferry. This impacts the urban area’s transportation infrastructure as customs, inspection, and security infrastructure are necessary part of the equation.

The international setting can provide a uniquely diverse population and cultural vibe to the urban area that may not be found in similar cities which are not positioned as a global transportation gateway.

Cities on narrows and straits are often vital trans-shipment points, where freight is transferred between ship and rail, ship and truck, truck and rail, or even in some cases even between air and truck or rail when the airport serving the urban area is across the strait. As a result, these cities may contain a significant amount of warehousing and storage space.

Due to the confined navigation channels, cities situated on a strait or narrow will often have strategic military importance. As a result, there may be army, navy, marine, and/or air force facilities that must be considered during region-wide planning and design programs. The Straits of Gibraltar, Hormuz, and Singapore are some obvious examples of straits with significant military and strategic relevance, as is the Bosphorus Strait separating Europe and Asia in Istanbul.

Crossing the strait or narrow has evolved over the decades from barges and ferries to impressive bridges or lengthy tunnels spanning the watery depths. This has helped relieve choke points that had delayed the cross-strait movement of goods, products, and people. Some of the world’s longest bridges and tunnels have been constructed or are under development across these narrows/straits. Here’s a brief list of some of the world’s longest bridges (by main span length) and the urban area where they are located:

For tunnels underneath straits and narrows, probably the best known example is the Channel Tunnel (Chunnel) under the English Channel between the United Kingdom and France. Some other examples are include the Queens-Midtown Tunnel under the East River Strait in New York City the Michigan Central Railway Tunnel underneath the Detroit River Strait between Detroit, Michigan and Windsor, Ontario. Tunnels underneath straits/narrows tend to be designed for railway usage.

Huge bridge or tunnel infrastructure projects not only serve to modernize the local transportation network and relieve traffic bottlenecks, but they also help knit the metropolis together and solidify it as an important and modern transportation hub. The ongoing political debate over a second international bridge crossing between Detroit and Windsor also demonstrates the need for both internal and cross-border cooperation.

The presence of the linear water feature such as a strait or narrow provides ample opportunities for water-based and shoreline-based recreational or tourism activities. However, precautions are necessary to avoid potential and dangerous conflicts with the operating shipping lanes and military facilities.

For those cities occupying both shorelines of the strait/narrow like New York City or Istanbul, consideration must be given to spanning the water feature with public and/or private utilities such as water, sewer, natural gas, electricity, cable, and fiber. In those instances where there is an international crossing involved, joint cooperation between nations is imperative.

Needless to say, there are numerous factors beyond those listed above that urban planners must take into consideration when envisioning the future of a metropolis which is set aside a strait or a narrow. As with every community dotting the map, there will be certain land use and other planning issues that are unique to the local situation. For the planner, it is their job to take the smorgasbord of issues and inputs and come up with a plan that best suits the needs and desires of their community.