Onward and spillward

‘The Lunacy Of Rebuilding In Disaster-Prone Areas’, Noema, April 25, 2024:

In the months after Hurricane Katrina, New Orleans proposed a flood control program unlike any other in U.S. history. Developed by the Bring New Orleans Back Commission, a diverse group of stakeholders appointed by the mayor, the resulting plan called for large parts of the city to be converted from longstanding residential zones to floodable parks. Released to the public in the form of a map, large green circles were positioned over neighborhoods where owners would be forced into buyouts. These were some of the most historic districts in a very historic city … and almost exclusively in majority Black and marginalized neighborhoods.

Christened in the press as the “Green Dot” map, the proposal ranks among the most profoundly unsuccessful plans ever issued by a municipal body and would never be put to a vote in the city council. … The Green Dot map’s remarkably brief tenure can be attributed in part to its proponents’ failure to adhere to the most basic rule of community planning: Never designate the where before building support for the what.

“Building support”. What a quaint idea. Everyone should be doing it the way India’s doing it: don’t ask anyone. That way “building support” is redundant and “where” starts to really mean “anywhere”.

‘Expert committee clears plan to rebuild washed-out Teesta dam in Sikkim’, The Hindu, January 28, 2025:

Fourteen months after a devastating glacier lake outburst flood in Sikkim washed away the Teesta-3 dam – the state’s biggest hydropower project – and killing at least 100, an expert committee of the environment ministry has recommended that the dam be reconstructed.

Instead of the older structure that was part rock and part concrete, the new dam will be entirely concrete – reportedly to increase its strength – and its spillway will be capable of managing a peak flow of 19,946 cubic metres a second (cumecs), thrice the capacity of the former dam, which was 7000 cumecs.

Sounds reasonable, right?

The new design incorporates a “worst-case scenario” – meaning the maximum possible rain in the upstream glacier lake, modelled by the India Meteorological Department, in the South Lhonak region over the next 100 years influencing further downstream modifications.

Now all we have to do is wait for the flood that will show up the IMD’s model — a fate models have often had to contend with this century, especially when dealing with rainfall.

‘The value of attributing extreme events to climate change’, The Hindu, May 24, 2024:

It is worth understanding how these ‘rapid extreme event attributions’ are performed. The most important concept is the change in probability: in this case, climate scientists contrasted the conditions in which the heatwaves occurred against a counterfactual world in which climate change did not happen. The conditions that prevail in the counterfactual world depend on the availability of data from our world. When there isn’t enough data, the researchers run models for the planet’s climate without increasing greenhouse gas emissions and other anthropogenic forcing. Where there is sufficient data, they use trends in the data to compare conditions today with a period from the past in which human effects on the planet were relatively minimal.

[But] the data are hardly ever sufficient, especially for rainfall, and almost never for extreme rainfall events. Climate models are also notoriously bad at properly capturing normal rainfall and worse at extreme ones.

Thus, the environment ministry keeps the gates open to a new dam with a 59,838-cumec spillway in future.