Modern rivers have become large drainage channels. The rain that falls on our living area is pushed away from the drains into the rivers as an obstruction.
This is because there is no more space for the rain to soak into the soil in our living areas. The result of forgetting to return the rain to the ground is the excessive amount of water flowing into the rivers, and when the limit is exceeded, the rivers overflow and flood the city.
This is not good, so we have raised the sides of the river and armed them with concrete to prevent the water from overflowing. It can be said, a forceful flood control. Hence, when the overflowing; limit is exceeded, we have to accept the enormous flood damage.
River overflows are caused by narrow, shallow, or slow-flowing rivers. But what I think is important is the amount of water flowing into the river per unit of time, because if it is too large, the river cannot handle the amount of water flowing into it, and it will easily overflow.
The key to flood control is how to reduce the amount of water flowing into the river per unit of time.
The Power of Rice Paddies
The rice paddy is a wet field for harvesting rice, and usually, a large amount of water is filled into it.
Most of the water supplied to rice paddy comes from rivers, but river water is usually contaminated due to the influence of human life. The river water supplied to the rice paddy slowly seeps deep into the ground, supplying organic matter to the soil. The infiltrated water is purified and joins the underground water veins.
This is similar to the principle of a slow-sand-filtration for obtaining purified water. The rice paddy functions as a biological device for purifying river water, and at the same time, by supplying purified water underground, it preserves the underground water veins and prevents ground subsidence.
In any case, rice paddy can hold a huge amount of water there. Even with the addition of water from the rains, the rice paddy can penetrate the water into the ground, thus keeping the amount of water constant. This means that water from rivers or rain can be stored in the rice paddy. It is as if the rain is stuck to the earth.
Even though it is not clear how much water the rice paddy hold, there is no doubt that it is a huge amount. In this sense, we can say that rice paddy is a “dam”.
The flood control mixed natural power
To prevent overflow from rivers, it is important to reduce the amount of water flowing into the river per unit time.
Dams in the upper reaches of rivers play a role in this. Rainfall in our living area is just pushed down into the river, so without dams upstream, the amount of water flowing into the river would be enormous and could easily exceed the limit.
From the perspective of flood control, it is desirable to have dams in our living areas, too. A practical solution is to set up rice paddy around the rivers. Normally, we can use the river water for irrigation, and it is expected to purify the water. When it rains, the rice paddy will hold water as long as they can. If the river were to overflow, the area would become dangerous, but since the paddy fields are uninhabited, what will be lost is the rice that was to be harvested, not human life.
Another practical measure to reduce the amount of water flowing into the river per unit time is to use rainwater tanks. These tanks can be placed at the sides of homes, schools, gymnasiums, etc. to store rainwater. The water is not suitable for drinking, but it can be used for gardening. In case of emergency, the water can be used for daily use by removing impurities with a filter.
I hope the world will continue to be a peaceful place where Noah's Ark is not needed.
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