Workers trapped in a factory in the West Midlands; the Gardener's Question Time summer garden party almost ruined by rain 'like stair-rods'; the death of a soldier swept away by a swollen river in Yorkshire; schools closed in Sheffield; and thousands of homes ruined in towns and villages from Wales to Norfolk. A century ago, these would have been called 'the big floods' for years to come but the sad fact is we'll probably see the same thing happen again before Christmas.

With good timing, inadequate investment in flood defences was highlighted in a report on Friday by the National Audit Office. They found that our defences – maintained by the Environment Agency – were in peak condition in less than half of high-risk areas, and that protection is often in the wrong place, defending farmland rather than centres of population.

And it isn't just the building of barriers to rising sea levels that is a problem. Other, seemingly harmless, land-use decisions can also have serious consequences in helping make floods part of our daily lives.

The trend to pave over front-gardens in London has led to a dramatic loss of surfaces that absorb water from heavy showers. The permeable land area lost recently is 22 times the size of Hyde Park, according to the London Assembly's Environment Committee's 'Crazy Paving' report in 2005.

Each decision to have a parking space rather than a front lawn has combined to increase the city’s vulnerability to flash-flooding several times. According to the Stern Review last year, “Each individual decision may be rational, but in aggregate this loss of permeable land will leave a legacy for future generations living in London.”

The risk of more city floods can only increase as climate change takes hold properly in the future. A month's worth of rain in 24 hours may never be 'normal' but we can expect it to be a regular occurrence.

In this new climate, plans to build homes on flood plains start to look like madness. With forty percent of homes in the South of England at serious risk of flooding already, building hundreds of thousands of new homes in the Thames Gateway (its name a bit of a giveaway as to its proximity to rising waters) makes no sense at all. The Stern Review recommended limiting construction on flood plains as a way of minimising the cost of climate change, but the government and London planners are intent on ignoring this advice.

Acknowledging its flood-defence failures to date, the Environment Agency is now looking for £150 million in extra funding from this year's comprehensive spending review. I hope they get this and more; a recent study in Scotland found that the psychological impact of losing treasured belongings in floods can take years to get over, lasting long after financial losses have been forgotten.

Despite the certainty of climate change in the future, property damage now is not inevitable. The great front garden tragedy in London could have easily been avoided with a small change in local planning guidelines, and was highlighted by the Greens in London very early on.

Similarly we've opposed the Thames Gateway approach to providing housing for London's growing population, pointing out that a combination of filling empty homes and building on brownfield sites can increase the supply of homes without pushing people into places that will be regularly under water within a decade or two.

The government needs a more coherent and comprehensive attitude to flood planning. If they fail, we could easily end up with large numbers of people unable to get household insurance, unable to sell their houses and condemned to a slow decline into poverty and slum housing conditions.

Arguably, government's 'job number one' is to plan for and provide secure homes for those who elect them. Things like flood risks are simple enough problems to identify, and the consequences of failure potentially so appalling, that the current culture of neglect is inexcusable. Will it take a much bigger tragedy, a British New Orleans, to sort this out?