Why is Houston so vulnerable to the devastating floods?

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Parts of the Houston area have been getting hammered by more than 50 inches of rain since Hurricane Harvey made landfall, setting new records for the united states. But why the city became America flood the capital?

In April 2016, “historic” floods struck Houston, a 17.6 in (44.7 cm) of rain fell on the city in a single day.

The flood came just 11 months after another massive storm hit the city, dropping over a foot of rain.

Together, these two events have caused 16 deaths and over $ 1 billion (£777m) in damages and interest.

Both pale in comparison to Hurricane Harvey, the impact of which was obtained Houston\’s unenviable reputation as the u.s. city most severely affected by the floods.

Understand why the risk to life and property is on the rise is crucial, not only for the future of the America\’s fourth largest city, but for others across the world who share many of its problems.Urban sprawl

Houston unleashed, the rapid growth is a primary factor.

The population of its metropolitan area of nearly 6.8 million people and, with the predictions of some of the countries with the most rapid growth for the coming years, it is expected to exceed 10 million by 2040.

The growth itself is not a problem, because it can create economic, social and environmental benefits for cities.

But poorly planned growth that fails to carefully manage the use of land for housing, businesses and infrastructure such as roads, parks and sewers that cities need to – can create problems and even lead to disaster.

Houston has long favored light-touch controls, which has led to haphazard development.

Today, the city covers an immense territory of more than 1 500 square kilometers.

He is the archetype of urban sprawl, where the land is easily accessible for real estate development on the city\’s expanding periphery.
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The loss of habitat

This unplanned growth has led to many problems.

One is that of vast acres of wetlands and grasslands, land that soak up large quantities of precipitation have been paved over.

Between 1992 and 2010, for example, White Oak Bayou, in the north-west of Houston has lost almost 70% of the wetlands.

During heavy rains, the city is growing expanses of concrete generate runoff that clogs and sometimes overwhelms its complex network of waterways. This includes creeks and bayous, as well as the risk of flood controls such as levees and detention basins.

Success of the wetlands and grasslands of the protection of the land would not itself have a major effect in the reduction of flooding caused by rains such as the one given by Harvey.

However, protecting and restoring natural areas provides an important contribution to making Houston less vulnerable to the most moderate of storms.

They also bring benefits to the environment by providing fish and wildlife habitat and clean up polluted runoff that can sometimes come from the city.

The blue color of water areas is detected before and after the storm.

A city for cars

Another problem is that the investment in flood control infrastructure, such as canals, dams, and reservoirs not managed to follow the pace of the expansion of the city.

Houston is a car-oriented city, with several billion dollars of projects in support of one of the most advanced systems of roads and highways in the world.

The goal is to make traffic flow more smoothly.

The time lag between the expenditure of flood prevention and roads may bring new challenges, fresh tarmac is laid for motorists.

An example is the partially completed State Highway 99.

Once completed this 290km (180 miles) of the loop will be the longest in the nation – surrounding the Houston area.

Continuation of urban sprawl on the edges of the city will inevitably follow, and without careful planning, wide expanses of impermeable concrete will be laid.

The runoff generated can cause problems for residents when heavy rains arrive.

For example, since the 1980s, rainfall has increased by 26% in the Brays Bayou watershed, but runoff has increased by 204%.

Another study suggests that a supplement of 3 500 households in the Sims Bayou watershed in the south of the city have been exposed to flooding due to increased runoff.

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What can be done?

The tragedy caused by Hurricane Harvey offers the possibility to plan for the reconstruction of a more resilient city.

The expansion of the city has led to short-term financial rewards for developers and builders, while local government has benefited from the increase in the tax base.

But they have not shared the risks presented by floods, whose costs are mostly passed on to residents and the national government.

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To survive on the Gulf Coast of Texas, in the century to come, the city and its surroundings, the region will need to make careful planning decisions to guide the growth.

A better coordination between the federal government, state and local government bodies is lacking.

The city will also have to take into consideration the way in which it defends itself against the storms. Make huge investments in flood control infrastructure they need to keep pace with the rapid expansion of the population.
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Everywhere in the world

While Harvey offers a dramatic, devastating storms are becoming more severe and more frequent throughout the world.

Rapid and poorly planned urbanization, the increase in the level of the sea, and the subsidence of putting the world coastal cities at increased risk of flooding.

A World Bank study predicts that the flood damage for large coastal cities could cost $1 billion a year by 2050 if no action is taken.

There are cities that offer a hint of what can be achieved in both the united states and elsewhere.

In front of more coastal storms, and rising sea level on the Atlantic Coast, in Norfolk, Virginia, has adopted long-term strategies to guide the future of land use and development.

For example, the areas of low flood risk where there has until now been limited development will be transformed into high-density and mixed income neighborhoods.

In contrast, the high-risk areas in established neighbourhoods gradually retired from banks, with housing purchases, while the main sewers and water utilities, and roads will be maintained and not expanded.

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Rotterdam, the netherlands, provides another model. Ninety percent of the population of the city is below sea level.

Its innovative solutions to the floods, living with water, rather than trying to contain it.

He has installed underground garages, green roofs that absorb water, water and places, which serve as a kind of aquatic town square, at the same time, huge storage tanks when extreme rainfall occurs.

From Norfolk and Rotterdam points of view, floods, and climate change are not obstacles to economic development, but opportunities.About this piece

This analysis was commissioned by the BBC to an expert working for an outside agency.

Philip Berke is Professor of Land Use and Environmental Planning at Texas A&M University.

Edited by Duncan Walker