Thailand's massive US$11.8 billion plan for a series of dams and canals to keep the waters of the Chao Phraya River away from Bangkok is drawing concern that it may be inappropriate, too expensive, and a gigantic magnet for corruption.

The government set out to put the plan in place after once-in-a-century floods in 2011 caused extensive damage, disrupted supply chains, nearly engulfing the central city. However, Japan's aid agency has presented an alternative plan that costs about half the price, and has questioned some of the assumptions and requirements in the Thai government plan.

Concerns have been raised about corruption because the government wants financing in place by June without putting the plans before parliament or it seems undertaking environmental and social impact assessments, with Pramon Sutheewong, chairman of the Anti-Corruption Organization of Thailand saying the project clarity and that he isn't sure how the money will be spent or on what projects.

Nevertheless, superficially the plans might reassure citizens, factory owners and investors that the government will do what it takes to prevent a repeat of 2011. Reassurance is essential to maintaining confidence given that the floods engulfed 1,300 factories on the Chao Phraya plain, which lies on average only 1-2 meters above sea level, compared to just 0.4 meters for Bangkok itself. The World Bank estimated that the flood resulted in US$45 billion of economic losses and another $15 billion in insurance claims.

The hard engineering approach laid out in the government's plans is if nothing else impressive for its scale, with spending estimates in current prices crudely equating to 78 percent of spending to rebuild the defences of New Orleans after Hurricane Katrina.

The scale and relative speed of the government's plans to deal with flood risks may hold significance beyond Thailand. In recent years Jakarta and Manila, which like Bangkok sprawl over and sink into flood-prone lands, have also been struck by severe floods, killing dozens and causing substantial losses to the economies. Thailand's plans may offer a benchmark for citizens and investors to judge efforts by public authorities in Indonesia and Philippines to secure their respective capitals from flooding.

There are however grounds for caution. If such hard-engineering approaches are to work, extensive data is required regarding the hydrology and rainfall of the region. The data may nevertheless be misleading, creating a false sense of confidence because the future is unlikely to be like the past for one inconvenient truth: climate change.

Two broad consequences stand out for tropical coastal cities, particularly those on marshes or subject to subsidence, such as Bangkok Jakarta and Manila. One, more frequent and more powerful storms are likely, plus higher temperatures and perhaps worse droughts. Two, sea level are rising because of thermal expansion and the melting of ice and snow on land with consequences for coastal erosion, saline intrusion into groundwater and fields, and drainage including sewerage.

In this regard the floods of 2011 offer a glimpse of what happens when the two come together. A large storm bringing heavy rainfall over several weeks intersected with high tides. Even if rainfall patterns remain relatively stable, rising sea and subsidence, around two meters in four decades after ground water extraction picked up in the early 1950s, suggest the probability of catastrophic floods will increase.

Detailed modelling of local conditions, such as that which accurately predicted the flooding of New York during Hurricane Sandy in 2012, does not appear to be readily available for Bangkok. Uncertainty in the dynamic nature of the relationship has to be accommodated in assessments of the relative merits of defend, adapt or retreat for an effective response to climate change.

However, plans put forward by the Thai government are characterized as flood management. Semantics perhaps, but words have power, and focusing on floods is likely to draw attention to the symptoms rather than the causes. Whether focusing on the latter may condition a different response is hard to say but logically it at least brings the driving issue to the fore.

The hard infrastructure preference, in contrast to a soft or ecological infrastructure approach, of the Thai government plans is a response of defence and adaptation. Taking this approach introduces effectively permanent fiscal, economic and environmental impacts as a consequence of developing hard infrastructure and subsequent requirements for maintenance and enhancement. Moreover, political lobbies may develop seeking to cement policy path dependency.

In making their choice, planners presumably judged that wealth generated by defending and adapting the existing physical structure of the economy in the city and floodplain will exceed the costs and deliver more benefits than the alternative of managed retreat and learning to live with rather than fight water. Delivering reliable engineering and management coordination of policies, agencies and governments at the scale and complexity required to defend and adapt to water has proven difficult worldwide. States like China and the United States may have won victories, at great cost, in this tussle with nature but outright victory is elusive. The Netherlands, after several centuries of pushing the sea back and reclaiming land, is changing tack, returning large areas to the sea while transforming communities to live with and on the water.

It seems reasonable therefore to question whether the states of Southeast Asia will succeed under conditions of intensifying climatic stress where those with greater resources have struggled in more benign times.

Under these conditions investors and homeowners might have reason to doubt the suitability and long-term prospects for hard engineering to deal with the evolving water situation. A precautionary stance would assume imperfect adaptation and plan for increasing frequency of floods equal to if not worse than those of 2011.

Firms may, despite government reassurances and infrastructure development, have to act for two reasons. One, insurance is becoming more expensive and may be withdrawn commercially from some areas, as is the case in particular for some coastal districts of the United States. Two, shareholders may take an increasing interest in the risks and costs of climate change vulnerability and demand a strategy. As Nick Robins of HSBC recently noted investors' concern about climate change is rising. Uncomfortable information is emerging from some corners of the insurance industry as well as civil society, for example the Carbon Tracker Initiative has been calling attention to the issue of stranded assets such as unburnable carbon resources.

Faith and expectations for the success of defence and adaptation, country risk and climate consequences, including flood losses, will have to be weighed against the costs of reorienting supply chains around sustainability and resilience.

That might, for example, mean relocating production facilities and management offices away to areas safe from floods and rising seas, perhaps the emergence of safeshoring in the design of supply chains. It might also mean considering which governments are most vulnerable to disruption. In this regard, Myanmar may stand out as a winner since the capital relocated far inland to Naypyidaw from vulnerable Yangon on the coast although for reasons other than mitigating climate change risk.

Adapting to climate change and the risks of defence and adaptation introduces new needs and wants, bringing change to markets. Inhabitants of vulnerable cities may welcome products and services for living through floods. Even if zoning regulations fail to impose flood-resilient design standards developers could earn a premium for offices, condominiums and apartments designed to function smoothly during a flood. Similar considerations might also apply to provision of public transport.

To some degree seemingly by accident it is already happening. Development of elevated railways and walkways, particularly in Bangkok, connecting offices, hotels and condominiums several storeys above street ? or flood ? level is akin to an emergent property of a self-organizing system. Given the outlook for flood risks this pattern of development may become commonplace in coastal cities.

Yangon, because it is relatively underdeveloped compared to places like Bangkok and Jakarta, has an opportunity to avoid building in vulnerability and to develop around the errors and missteps of similar cities in Southeast Asia. Whether the government develops a climate strategy for sustainability and resilience which embraces the physical and financial advantages of soft and ecological infrastructure as well as stipulating building codes premised on living with floods remains to be seen.

Floods wrought by more severe storms and rising seas are perhaps the most significant consequences of climate change for coastal cities, particularly in developing countries like those of Southeast Asia. As scientific understanding and experience of the consequences develop the response equation for individuals, firms and governments will evolve, at times starkly.

Given the consequences and current trends heading towards 4-5 degrees Centigrade of warming this century, highlighted last November by the World Bank and PwC, the time to act to reduce risks and exploit opportunities in the cities and flood plains of Southeast Asia is now.

(David Fullbrook is a sustainability economist.)