Damn the dams - a concise, simple explanation of how dams cause flooding (and Thailand's worst, and current, natural disaster)

Back in the Great Depression, FDR’s answer to a lot of problems was dam building: the TVA (Tennessee Valley Authority), established 1933, a massive program of building dams, hydroelectric generating stations and flood-control projects. It put a lot of people to work (like the 1935 Work Projects Administration, WPA), and remained held in a largely positive light throughout my youth. The Monarch of Th ailand instituted a similar program, which also seemed to work. What was overlooked is that many reproductive cycles are coordinated with flood cycles, the floods spread nutrients, the sediments which previously nourished the environment now silt up behind the dams (as does debris that previously provided food for a variety of organisms), and local temperatures are changed. Not only trees, fish and birds are affected, but micro-organisms, insect life, and other less popular, and loveable forms of life (which remain, nevertheless, important).
In recent years, floods seem to have been very much more destructive than usual, and in Thailand now, the flooding may come to be seen as the largest natural disaster the country has ever experienced. Containing water-flow within concrete embankments doesn’t reduce the volume of flow, but it just increases the rate of flow – dramatically. Water which cannot spread out, bend in its course, and meander peacefully, builds up angry power. Floodwaters become literally propelled downstream and, inevitably, the damage done to flood plains below is increased. The problem is exacerbated by deforestation and development which come with, or right after, cement utilization projects intended for flood-control.
Root systems acts as a vast sponge, and release water only very slowly, acting as a natural regulator to water channels. This tends to disappear with “development” – the root system of a golf course simply won’t help much (development, and having too many kids, as counterproductive). Human intervention has caused the runoff proportion of rainfall to vastly increase, almost unbelievably, to at least 90% more. Small amounts flowing slowly have now become huge amounts flowing swiftly. And our soil is rapidly losing its structure, becoming very vulnerable to erosion by wind and water. Silt accumulates, raising the height of river beds until they become higher than the surrounding land. China’s Yellow River, in the Yellow plains, now flows five to ten meters above ground level – in non-flood times! And raising the height of embankments only increase the severity of future floods.
As usual, I’m not providing a solution, or even new insights or knowledge. I’m merely trying to clarify our situation, by providing an easily absorbable description and analysis.
Negative effects of large hydroelectric dams include:
1. Death and destruction from flooding
2. Displacement of people and wildlife
3. Large amounts of plant life are submerged and decay anaerobically (in the absence of oxygen) generating greenhouse gasses including methane.
4. Migratory patterns for many animals are disrupted (or worse)
5. Dams hold back sediments which fertilized lands downstream, so now farmers use dangerous chemical fertilizers and pesticides to compensate
6. Salt water now intrudes into deltas
7. The reservoirs are breeding grounds for mosquitoes and otherwise assist in disease spread
8. Dams serve as a heat sink: the water is hotter than normal river water. This warm water, when released, can affect animal life and other things.