How to deal with droughts, floods, and storms

There are many areas where the rainfall is very seasonal. For example, the large regions where there are seasonal monsoon rains. During the rainy season, there is lots of water available; in fact, there is often way too much water, so that there are disastrous floods with loss of life and property. But during the dry season there is not enough water to raise crops or support marine life.
In areas where there are rivers in deep valleys, it is possible to build dams to store the extra water. But this cannot be done in flat areas. But there are things that can be done even in flat areas, to reduce the problems caused by this seasonal or intermittent rainfall. In regions that are mostly flat, such as Bangladesh, (which is mostly on a river delta that is now barely above sea level), it seems that a good plan would be to provide seasonal storage of large amounts of water. This would not be easy, but there would be many benefits. One way to do this would be to start in the beginning of the dry season, excavate a large area as deeply as possible, use most of the removed material to surround the excavation with a high levee and protect the levee with impermeable material such as common tarp fabric. This will create an artificial lake basin. The size of the lake that can be created in this way depends on the availability of a large amount of earth moving equipment so that the entire lake basin can be created in one dry season. After the levee is created, continue to excavate more material to raise the level of the surrounding area. Excavate as much material as possible before the rains begin.
When the rains come, and the rivers swell, use massive pumps to fill the lake with water from the rivers. This avoids the usual flooding for two reasons: one is that the area around the lake is now higher because of the added material that was deposited there after it was removed to make the lake, and the other reason is that the excess river water that would have contributed to the flooding has now been pumped into the lake which should be filled to the top of the levees. The lake will now have a level well above the surrounding land. During the following dry season, the lake water can be used for irrigation and other needs. The lake can also be stocked with fish, such as tilapia, so that it will produce food as well.
The following dry season, the same equipment can be used to create another lake. As more lakes are created, larger areas are protected from flooding. The elevated land will also provide protection during the periodic cyclones (hurricanes) that usually flood the land with seawater and often cause major loss of life due to drowning. The sea water deposits salt in the soil and makes it less productive until the salt is washed out, which usually does not happen until the following rainy season. The fresh water in the lake can be used to wash the salt out of the soil. Even if the raised land is not high enough to avoid flooding in the storm, the area covered by the levees will be much higher and can be topped with concrete storm shelters that will protect the local population. The levees will also have sufficient area to keep livestock out of the flooded area. The loss of livestock is now a major economic cost of the cyclones.
It will be necessary to periodically add silt to the land. This happened naturally during the seasonal floods and it kept the land fertile and maintained the level of the delta. But now that the land is no longer getting flooded every year, this silt must be added artificially. Fortunately, this will not be difficult to do. When the waters of the swollen rivers are pumped into the lakes, the silt that the water carried was also pumped into the lakes. This silt will settle out onto the bottom of the lakes and if it was not removed, eventually it would fill the lake basin. This is what happens to lakes behind dams all over the world. Eventually, these lakes fill with sediment, and the dams can no longer store water. To prevent this from happening, the silt must be removed. Fortunately, the silt is needed on the land around the lake and it can be easily be moved to the land where it is needed. This should be done during the dry season. The way to do this is to pump water from the bottom of the lake that has been mixed with a large amount of the sediment that was carried by the water that filled the lake. This sediment must be mechanically stirred into the water. This pumped water will be mixed with as much sediment as it can carry and it should be used to flood a small area in the vicinity of the lake. As a result, this area will be raised and fertilized. The following year, this area will support high agricultural productivity. Each year the same thing should be done to a different area. The result will be that the delta will be gradually raised, it will be periodically fertilized and the lake will not fill with silt. In fact this process can even be used to make the lake deeper so that it can store more water this procedure will result in a stable long term productive and safe area which can support many people
Obviously, this is not a cheap project. It requires massive earth moving equipment and pumps, and the energy necessary to run them. However, it will be seen to be a good investment when compared to the cost of the flood damage and the life and health consequences of not doing it. It will also increase the dry season agricultural production that the irrigation water makes possible. There may eventually be some difficulty getting fuel for the earth moving equipment as CO2 limits become more common and fossil fuel become less available, but during the dry season when the equipment is used, there should be ample sunlight to produce power. Earth moving equipment should be easily modified for battery operation because this type of equipment does not have to move far or fast and weight is usually not an issue. There are already totally electric busses used in California that can be recharged in a few minutes after completing their runs. The power needs of earth moving equipment should be similar to the needs of the busses. The addition of the solar panels necessary to provide electric power for the earth moving equipment will also provide shaded areas that can be used by farm animals as protection from the hot daytime sun. When the earth moving equipment is not actively using the power, it can be used by the community. When the lake is finished, the earth moving equipment can be moved to another area to create more lakes.
As rainfall patterns change during the global warming transition, there are frequent floods and also droughts in areas that have been accustomed to more predictable weather. Australia, Texas, and other places in the US Midwest have had droughts that were followed by wildfires that burned the dry vegetation and could not be stopped. The same areas were also subject to record breaking rainfalls that caused severe flood damage. This type of weather pattern is expected to recur. Therefore, the creation of artificial lakes, as described above would be a cost effective way to deal with both the water shortages and the flooding. Both earth moving equipment and pumps would be needed, but just as in the monsoon areas, the cost would be far less than the damage caused by the severe weather.
In another article in this blog, (Heat pipes and uses Revised) there is a description of a method for getting free air conditioning that also utilizes a large pool of water. This water can also be used for fire protection. It can even be used to provide water for an automatic system that enables homes to protect themselves from wildfires.
In the eastern USA there are sometimes very heavy rains caused by hurricanes that cause flooding over large areas. The floods are caused not only by the rain, but also by the storm surges that are caused by the hurricane winds. One area that has been affected in this way is southern Florida and the gulf coast. But builders in that region have developed an effective solution that permits residential development, flood control, and high land values. That solution is to raise the level of the land by creating networks of canals. The canals are created by excavation and the removed material is used to raise the level of the land near the canal. This makes the land more valuable for home building because it no longer floods and also because all of the houses are now waterfront properties, and residents can have boat docks in their back yards. In this way, areas that were low value swamplands have been converted to high value residential properties. The canals drain into the ocean, but the drains are controlled by movable gates. This makes it possible to control the water level in the canals and also to block storm surges from the ocean so that the canals do not overflow during hurricanes.
In areas of river deltas, this technique could still be used, but the different character of the land must be considered. In Florida, the land is composed of ancient coral and seafloor deposits. This means that it does not subside easily and the raised land around the canals will be stable. However, the material of river deltas is composed of soft silt that was deposited by the river and which tends to sink as the water in it is reduced by compression. The silt is also easily washed back into the canals by rains unless the surface is stabilized by dense vegetation. This means that, while it is possible to create canals, they are difficult to maintain and may need to be periodically dredged and have the material re-deposited on the adjacent land.


Bill Isecke