Is it possible to protect cities from the kind of devastation caused by Typhoon Haiyan in Tacloban city, central Philippines? There, storm surges reached up to the second floor of buildings. Over 10,000 people are feared dead. Almost all infrastructure has been knocked out. One year after Hurricane Sandy New Yorkers are asking themselves the same question.

This type of extreme event is likely to increase in frequency as global sea levels are projected to rise by up to a metre by 2100, according to the UK's Natural Environment Research Council (NERC)'s Proudman Oceanographic Laboratory (POL), a world leader in storm surge modelling.

But investment in storm surge protection is expensive. It can however be justified twofold: not only is it critical for protecting a city's population but its economy too. According to NERC, a city deemed by investors not to be sufficiently protected from flood risk would see their money flowing elsewhere: they calculate that a 5% fall in Foreign Direct Investment due to perceived flood risk would cost the London economy £2.1 billion per annum.

The Dutch, of course, are leaders in this field, with Zuiderzee and Delta Works projects, manmade systems of dams, land reclamation and water drainage works, declared by the American Society of Civil Engineers as among the Seven Wonders of the Modern World. New Orleans has already seen the adoption of Dutch principles for its $14 billion upgrades to the levees.

Firstly, it is becoming increasingly foolish and shortsighted to situate critical infrastructure close to sea level. Resiting of population centres and critical infrastructure to higher ground will be an increasing priority of coastal cities. Resources should then be concentrated on protecting sites that cannot be moved. 

Complex modelling comparing the relative environmental and economic costs and benefits of protecting different areas of land is required to tease out strategies and priorities for action. Decisions will be based upon variables such as height above sea level, relative population density, water flows and gradients, underlying geology, and the presence of critical infrastructure such as power supplies, industry, chemicals plants and bridges.

For example, what would happen if a storm surge the same height as that which struck Tacloban hit Texas City and the surrounding coast? Much of it would be submerged, as can be seen from the illustrations below. How can you protect against such high waves, especially when the coastline is so convoluted?

One proposal to protect the Houston Ship Canal levee is a $1 billion scheme similar to that used in Rotterdam [Gulf Coast Green - 2013 Coastal Planning and Design for Sustainable Economic Development, Recreation, and Security Thomas Colbert, University of Houston].

In Galverston Bay situated in front of Texas city, an earthen verdant levy could also rise to 25 feet above sea level with a 1 to 5 gradient. On the protected side existing residences need no modification. On the Bayside, existing saltwater wetlands are preserved. New wetlands should be constructed to replace those already lost to development, says Colbert, who grew up in New Orleans where, during hurricane Katrina, his father had to take shelter in a building that ran out of drinking water.

He also points out that marshes are essential to reduce coastal erosion. Tall grasses that are found in wetlands reduce the scouring effect of storm surges while providing essential habitats for hatching fish and migrating birds. They also provide leisure facilities for humans.

There is a prospect for new types of architecture in the form of elevated structures on the bay side of levees, built on tall stilts, which would in some cases be needed to peer over raised existing sea walls, made 8 feet higher.

A mixture of approaches is therefore necessary for dealing with the threat of storm surges. Besides sensible urban planning, this includes, wherever possible, deploying nature's own adaptation and mitigation measures in the form of wetlands; different patterns of development; and, above all, flexible, modular and upgradeable technologies.