How unusual are the Thailand floods?

Floods in Bangkok in 1983 (source)

Some good rapidly-updated english-language sources of information about the Thailand floods are at the 2bangkok forums. One article that particularly my attention was this one comparing the current floods to the floods of 1983 and 1995. The article starts with a criticism of the shortsightedness of the solutions to the flood problems. The criticism wasn't for the 2011 flood however. The author says-

The article was headlined "Flooding is a result of bad planning" and could well be placed on the news pages of the same paper today, without anyone noticing it is 16 years old. It should have been prophetic.

In those past events Bangkok was flooded for several months. To put this in perspective, Hurricane Katrina flooded New Orleans for about two weeks. This year Brisbane was partially underwater for three days. 

Not only are events repeated over time, but I have been noticing common themes in different countries so far. Bangkok, Manila and Jakarta all have issues with infrastructure trying to keep up with rapid growth, especially with poor squatters living along the riverbanks. The ties between poverty and vulnerability to floods run deep.

All the cities are near sea level and are relatively flat, so when floods come, high tides prevent water from flowing out. This is getting worse with subsidence from groundwater pumping (i.e. the cities are sinking as drinking water is extracted from the ground). The problem was so bad in Jakarta that the city had to build a new highway for cars going to the airport because the old one was effectively always under water (and sinking at about 0.8 ft, 25 cm per year).

In the background is Jakarta's "higher highway", built because of sea level rise and subsidence

A few days ago, a hotel clerk suggested that the Thailand floods were being made worse by land use change and cutting down forests upstream, a problem that was mentioned in all the countries we've been in so far. An article on the "Politics behind Thailand's floods" strikes another familiar chord:

Different ministers issued different warnings. Inter-agency conflicts and lack of policy co-ordination were rife. [The Prime Minister] Yingluck delegated and skirted around tough decisions. Her strengths of patience and even temperament became her weaknesses. Information was not centralised and reliable. The saturation and sensationalism of television images on a constant news cycle made the public edgier...

The floods also have underlined Thailand's urban-rural divide which has underpinned a broader national polarisation and conflict since [Past Prime Minister] Thaksin's departure [after the 2006 coup d'etat]. Downstream provinces were awash in order to divert waters away from central Bangkok. The Thai capital was kept mostly dry at the expense of its surrounding areas.

The difficult decision to sacrifice rural areas to save cities (by blowing up dikes) was a central theme in "Rising Tide", a book about the 1927 (!) floods in Mississippi. Indeed, just like how the dikes were under armed guard in 1927, the headline on this morning's paper was that the Bangkok flood defenses were declared off-limits to the public. Aside from sabotage, the fear was that people would come argue with the dam operator that was flooding them (a concern we also heard in Jakarta).

While there are common threads to every country it seems, a major challenge for decision-makers and the public will be to make the best use of science to quantify which of these many factors is the biggest problem for a specific area. Furthermore, it doesn't seem enough to suggest the usual suspects of solutions (bigger dams, dredging, reforestation, land use planning, preventing climate change) without knowing which is the most appropriate/effective for a given region.