Here we go again. It rains in Britain and an emergency is declared. Nearly 600 flood warnings are issued in England on a single day and the environment secretary, George Eustice, declares it impossible to “protect every single household”. But he can protect the Met Office. It is to get another £1.2bn of public money for a “supercomputer”, just six years after getting £97m for a previous one. There seems to be no headline-grabbing project for which this government is short of a billion.

Except for coastal surges, floods are about rivers. These have flooded throughout history, and there is no mystery as to why. It is called gravity. Rivers drain catchment areas into flood plains, moving water from uplands to lowlands. Variations in their behaviour are the result of the past planning of those same rivers and flood plains. Whatever may be the role of the climate emergency, blaming it is of no help to victims of today’s flooding.

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When Cockermouth in Cumbria was submerged in 2009, it was clear that a prime cause was the expedited drainage from Lake District hill farms to promote grazing pasture. When the Somerset Levels were flooded in 2014, a prime cause was the change of use of surrounding hills to growing high-density maize, exposing soil to runoff. Likewise, subsidised conifer plantations have everywhere debased vegetation and produced irregular spate rivers.

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As for building retaining walls to protect riverside communities, this merely shifts volume downstream. Here it meets the readiness of local planners to build houses in flood plains. The sprawl of housing estates is now urged on councils by a fanatically anti-planning government. As a drive across the aforementioned Somerset Levels will show, the result is acres of accidents waiting to happen. There is nothing a flood likes more than a good stretch of concrete.

Hence these floods are not acts of God, they are, in large measure, acts of government. For the most part, they are preventable by upland river management and lowland common sense. The National Trust responded to the Cockermouth disaster by slowing runoff from the hills, despite farmer opposition. The disaster has not been repeated. The rewilding movement seeks to promote variegated vegetation and retain water in peatland. Beaver reintroduction, now operating from Angus to Sussex to Devon, has shown remarkable results in damming streams and slowing flow. It can be done.

In other words the answer to flooding lies in a thousand frontline measures, aimed at correcting decades of foolish policies. The trouble is that a thousand measures lack the glamour of a £1.2bn computer. Flood victims can only look on in envy, and wonder how many lost sofas, beds and kitchens that money might have bought.

• Simon Jenkins is a Guardian columnist