Late autumn
A Shift in our Way of Thinking from the "prevention of disasters" to the "reduction of disasters"

This year, we have learned a lot of lessons from the frequent disasters caused by abnormal weather, not only in Japan but also all over the world.

The large-scale flood which caused so much damage to Fukushima Prefecture again after twelve years, was mostly caused by inland water. After the flood of twelve years ago, main embankments were firmly constructed, but water from small and medium-sized rivers designed to flow into these embankments was not allowed to reach there for various reasons including the fact that no pumps were installed in vital places.

If we strengthen some sections of the bank, then other weak sections are broken---that is a lesson we have learned again from this year's flood. The more we strive to confront nature, the more nature strives to defeat us.

Recently I had the opportunity to listen to a talk concerning flood plains (retarding basins) from experts in this field from America and Germany.

According to them, they discarded the past practice of building banks near the waterway; their current task is to build the bank at rather remote places from the water flow so that they could enhance the total strength of the river against flooding.

To do that, they have had to check the changes of the past water channel of the river for these several hundred years, and they have built banks at the farthest left and the farthest right of the river so that the capacity of the river could be increased.

As a result, there was a wide area for a flood plain (retarding basin) within the two banks. The current challenge is how to utilize this plain for public purposes.

Flexible measures in tune with the power of nature

Recent attempts in the world to prevent disasters seem to adopt flexible measures in tune with the power of nature instead of trying to conquer it.

In other words, we should stop building a "rigid infrastructure" to prevent natural disasters; instead, we should try to build a flexible structure for reducing natural disasters as much as possible in order to get rid of the above-mentioned vicious circle.

One is reminded of the experience of disaster-reducing effects in "Minuma Tanbo" in Saitama Prefecture.
When the Shiba Kawa of Saitama flooded at the time of Kanogawa-Typhoon in September 1958, it is said that the flooding in Kawaguchi and Toda cities remained relatively light because Minuma Tanbo pooled and held about 10 million tons of water for several days.

As a result, the 'natural' flood plain of Minuma Tanbo was well recognized and the "three principles of Minuma" (which did not allow the land to convert into a farmland) was formulated.

When we shift our attitude from preventing disasters to reducing them, we notice that there are various accompanying benefits resulting from such a shift of our attitude.

With the conventional way of river improvement, there is open space remaining outside of the banks after the improvement. On the contrary, with a flexible disaster-reducing infrastructure, we could have open space inside the banks.

The space cannot be used for production activities or as living space.

Naturally it will have an enhanced value as an ecosystem space.

Or it could be used as a kind of communal or hobby farmland for the public affecting no one's livelihood.

Realizing abundant green space around cities at river deltas
In the past, most places at river deltas in Japan are narrowed with river improvement works. Open spaces outside of the banks thus created by the river improvement could be used to enlarge the city area for housing or any other urban development.

If we could materialize river delta cities abundant with green space following our above-mentioned "paradigm shift", this might be a revolutionary breakthrough in future city planning.

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