INTERACTIVESee how Houston has developed since 1984

2017

1984

Growth itself is not a problem, as it can create economic, social and environmental benefits for cities.

But poorly planned growth which fails to carefully manage land use - for housing, businesses and the infrastructure like roads, parks and sewers that cities need - can create problems and even lead to disasters.

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

The city now covers an enormous area of more than 1,500 sq km.

It is the archetype of urban sprawl, where land is made readily accessible for real estate development on the city's ever expanding periphery.

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Loss of habitat

This unplanned growth has led to many problems.

One is that vast acres of wetlands and prairie land - which soak up large amounts of rainfall - have been paved over.

Between 1992 and 2010, for example, White Oak Bayou in north-west Houston lost about 70% of its original wetlands.

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

Successful wetland and prairie land protection would not itself have a major effect in reducing flooding caused by unprecedented rainfall like that delivered by Harvey.

Yet, protecting and restoring the natural areas provides an important contribution to making Houston less vulnerable to more moderate storms.

They also bring environmental benefits - providing fish and wildlife habitats, and cleaning polluted runoff that can sometimes enter from the city.

The artificially blue-coloured areas show water detected bef