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The picture collage shows some of the damage wrought by flood waters in Harare’s Carrick Creagh Estates and Borrowdale Brooke. The raging flood waters tore into houses, breaking window panes and doors and in some instances washing away property such as refrigerators, couches and television sets. Trees were uprooted, a bridge was swept away, pre-cast walls collapsed while the floods also swept away crops and livestock. — (Picture by Innocent Makawa)

The floods in north-west Borrowdale and a few parts of Glen Lorne last week after a very heavy downpour are the direct result of poor planning by developers and approved without investigation by the Harare City Council with the perimeter walls blamed by the council being very much a sideshow.

Indeed, a Government water engineer noted that a wall only blocks a water course if built across that water course.

We would imagine that if the wall that floods breached was not there then the house behind the wall was in the water course and would still be flooded. The attempt to shift the blame to house-owners simply does not make sense.

What should have happened, and what must now happen, is that development in water courses has to be banned or water courses have to be diverted. At the same time, developers must be forced to think through the effects of their projects and ensure high runoff can be taken to the nearest stream or river promptly.

In most of Harare, including all the older sections of Borrowdale, this is largely automatic. Most of the city was built on a rectangular grid system, seen at its most intense in the city centre, which, being almost entirely built over a stream, has to cope with every drop of rain turning into instant runoff. But from Highlands to Highfield, if the stormwater drains overflow in a bad storm the road network itself can cope with the overload and the grid ensures that floodwater quickly finds a road leading to the nearest stream or river and is drained. Potholes are worse but homes, shops and factories are not flooded.

And the streams and rivers in older areas were often deepened and widened to ensure that the floodwater was moved quickly without causing damage to property. Most houses now have walls and these do not cause floods.

There were floods in Msasa a few weeks ago, in an area that does not have a rectangular road grid, but these were largely due to the fact that the drains built in the 1950s and 1960s had been blocked with rubble and garbage, thus letting Msasa cope with the storm over southern Greendale without a proper outlet to the Mukuvisi River. But past bad storms had been handled there.

Newer Borrowdale was more complex. First, the older developments on the hillsides now allow subdivision, more houses and more runoff. The old drainage and road grid gets this extra water away efficiently.

But instead of farms in the flatter valleys there are large housing developments, often using fancy landscaping and long meandering roads rather than a grid.

The floodwaters from the hills, and the high runoff from the heavy valley development, cannot reach rivers such as the Borrowdale Brook quickly. So there are floods, and lives are exposed to avoidable risk.

What this newer area of Borrowdale needs, and other new areas need, are careful engineering surveys to ensure that when there is a heavy storm, or a succession of storms, runoff is moved quickly to a river and future developers are forced to submit plans in advance that ensure storm water from the development, and more importantly, from high ground next to the development, is moved efficiently to the nearest river.

There is nothing hard about this. People have been building towns and cities for thousands of years and when they think it through there is no flooding and when they do not care there are floods.

Harare City Council needs to care. And this starts with the city’s planning and engineering departments doing their job instead of getting bribes to approve improper plans.