Waiting for the water
Posted - November 01, 2009
Parts of Jericho at flood risk
Residents living close to the canal received rather alarming news a few months back. The Environment Agency sent out a notice warning that the lower parts of Jericho, effectively all houses between the canal and Hart Street, were now considered at risk of flooding.
At a meeting for residents, officials from the Environment Agency explained that they had issued the new flood map not because of any fresh developments, but because they now had more accurate data on potential water flows.
What are the chances that those of us living within what is now categorized as ‘Flood Zone 3a’ will get our feet wet? The Environment Agency warnings suggest we have a 1% chance of being flooded in any year. Or to put it another way, maybe once in a hundred years.
In 2007, we seemed to come close to this, as the level of water from the Thames approached that of the canal. Another six inches might have done the trick. But in fact, according to the Environment Agency, it might have taken at least two or three times as much water to start flooding lower Jericho. This is because the first impact of more water arriving from the north would be to increase the speed of flow rather than raise the level.
A close thing in 2007, as the river surges close to the top of the Isis Lock. Photo Adrian Arbib
Jericho does have some history of flooding, but this was a result of water coming from the other direction, flowing down the hill from Walton Street. Among other things this was because the construction of the canal had blocked the drainage. However, in the 1970s the water authority installed a new drainage system along with a pumping station in Nelson Street, which solved the problem.
Until recently there seemed to be little risk of water coming from the west. The lower part of Jericho used to lie within the Thames flood plain, but the canal now offers a barrier and the land is probably a little higher than before, maybe 30 centimetres. Meanwhile Port Meadow still soaks up a lot of excess river water.
The flood possibility – that we might not be as secure as we thought – arose first from discussions on the development of the canalside site. As part of the community case against the redevelopment, the Jericho Living Heritage Trust and the Jericho Community Association carried out a flood risk assessment which showed that the northern part of the site is lower and vulnerable. It is clear too that more intense and sudden rainfall further up river, perhaps as a result of climate change, could leave us more exposed.
One implication for residents is more expensive house insurance. Thus far there does not seem to have been a problem. A number of residents have dutifully reported the news of the revised flood map to their insurance companies and have been told that insurers would already have this, or better, information. Indeed it seems that they are more interested in knowing if there has been any recent history of flooding in Jericho – and since there has not been they do not appear particularly concerned. Of course the ‘one year in one hundred’ could be 2010.