The Linebacker Theory of Urban Defence

Fortifications at castles and walled cities have given way to more permeable edges at urban settlements.  But at the critical water’s edge, strong building walls—mass and material in defiance of rising waters—offer assistance in resisting the immediate effects of storms.  Concrete and steel buttress against tides and wave action, and intercept the debris which would otherwise pierce lighter frames.

Multi-story casino developments along the waterfront protected single-family houses in Hurricane Katrina, saving lives as well as structures.  One 28-story hotel tower and its 4-level parking garage shielded an urban area three blocks deep, intercepting the Category 1 winds and Category 3 storm surge and diminishing the impact upon the buildings in its lee.  Beyond the tower’s protection, modest wood cottages were propelled off their foundations, roofs were ripped from the walls, and structures were reduced to debris.

In contrast, the commercial structures suffered damage to lower floors and broken windows throughout, but the hotel tower and garage remained intact.  The structures were six years old, built with the fire-proofed and reinforced techniques standard for commercial investments.  The casino functions were required to be placed on movable barges; these massive, floating palaces were tossed thousands of yards by the tidal suck and sweep.  The inability for casinos to recover quickly and the general blow to coastal tourism lead to a significant loss of revenue for the state of Mississippi, and inspired changes to the gaming laws.  (The state no longer requires water-borne gaming along the coast.)

Improvements to building strength are available, but they come with a higher initial cost than standard construction.  In 2010, in Mississippi, a commercial structure budgeted at $200.00 per square foot for conventional construction would rise to $250.00 to $350.00 per square foot if armoured to meet tornadic windspeeds and debris impacts, and raised on a hardened base.  Even nominal increases in safety, such as upgrading from standard facilities to essential facilities as defined by the building codes, requires a premium of 10-25 percent higher costs.

When a storm strikes, higher initial investments may demonstrate their worth many times over.  Lower capital costs are required for repairs necessary to return to operation.  There is reduced downtime for employees, and a bonus for the first businesses with the ability to bounce back.

The same issue driving down reinvestment along coastlines—higher insurance prices—may promote higher standards for coastal structures.  Insurance costs for buildings within flood zones are set to multiply, due to reduced government subsidies.  Underwriters don’t want losses, thus insurance companies are beginning to discount policies for buildings with better materials and methods.  People don’t want higher costs and may be willing to pay more upfront, with the promise of lower rates annually, multiplied over many years.

A desirable view inflates property values and property taxes keep pace.  Soon, only wealthy individuals or collectively owned property may occupy the water’s edge.  Can the stratification of wealth along coastlines be utilized to protect smaller-scale, individual structures behind a first tier of armoured structures?  Can continuous urban development encourage greater density along the water; admittedly closer to danger, but immunized by higher performance standards?  Could dense patterns of inhabitation and small lot sizes reduce storm surge and debris in future storms?

Similar conditions are found in cities far from Biloxi, offering evidence that this strategy works.  Dense infill breaks the impact of water and scatters the wind.  In Mumbai, mangroves and wetlands providing natural defences have eroded to make room for new real estate, housing the city’s 13 million residents clustered at a rate of 53,600 people per square mile.  Coastal Regulation Zone guidelines attempt to keep lower densities within 500 meters of the shore for traditional uses: fishing villages and working industrial waterfronts.  But what if that guidance was reversed, and higher densities allowed provided the structures met higher construction standards?  This may be a more appealing solution than the current estimate of 40 billion rupees necessary to replace the city’s storm drainage and flood defence systems.  At the very least, developing a string of (hardened) pearls assigns both the risk and the higher initial costs to be borne by the residents most able to meet the demands of waterfront living, instead of spreading the cost across the over 60 percent of the population living in informal settlements with barely a sheet of corrugated metal between them and the elements.

There are other cities and beaches from Miami to Waikiki, Beirut to the south of France, with a continuous corniche of hotels, apartments, and condominiums.  These inhabited breakwaters shelter small, lightweight dwellings behind the front tier.  With proper flood gates installed to seal the gaps remaining at streets and setbacks, this strategy has the potential to halt surge at the first band of structures instead of allowing it to pass beyond and cause mayhem.  If cities place stronger structures seaward, the altruism inherent in the urban condition protects the smaller and weaker buildings beyond.