Indonesia says its giant sea wall will stop flooding. Is this climate adaptation or a costly folly?

[John Nissen]

Indonesia says its giant sea wall will stop flooding. Is this climate adaptation or a costly folly? https://share.google/LYoc7PYM5QLkfbdNR 

[Veli Albert Kallio]

North-Western Java is exceedingly urban with 85 million people living in Jakara and it satellite townships; more populated than the Netherlands. There are 20 million or more within about one metre above sea level. Typically clusters of skyscrapers are separated by 5 to 15 minutes drive with small houses and blocks in between. The fused urban area goes for about 200 miles non stop. By all means sea wall is seen as the solution against coastal flooding as the sea level is rising.

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From: healthy-planet-...@googlegroups.com <healthy-planet-...@googlegroups.com> on behalf of John Nissen <johnnis...@gmail.com>
Sent: 24 May 2026 20:12
To: Planetary Restoration <planetary-...@googlegroups.com>
Cc: healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>
Subject: [HPAC] Indonesia says its giant sea wall will stop flooding. Is this climate adaptation or a costly folly?

 

Indonesia says its giant sea wall will stop flooding. Is this climate adaptation or a costly folly? https://share.google/LYoc7PYM5QLkfbdNR 

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[Paul Klinkman]

Dear Action Coalition,

My instinct leans strongly toward costly folly.

It's not the sunny day king tides that can ruin the homes and the lives of millions of people, it's the rapidly growing tendency of super-typhoons to rapidly intensify.  Build a five meter wall and you'll certainly get six meters.  Build an eight meter wall and then thirty years from now you'll be shocked with ten meters of storm surge topped with waves.  If your town ever sees 300 km/hour wind gusts, you already won't have much of anything left to protect from the rising water.

The other problem with building in resilience is political corruption.  In 1965 the U.S. Congress ordered the country's Corps of Engineers to make the City of New Orleans safer.  They didn't do the job.  Hurricane Katrina hit not as a Category 5 hurricane but as a Category 2 hurricane, and 1392 people died.  So, who is about to make sure ahead of time that the wall will stand up to a real hurricane?

Yours,

Paul Klinkman

[John Nissen]

Hi Paul,

You are right.  The short-term flood risk comes much more from the intensity of storms and high precipitation events than from sea level rise.  This has been taken into account by Climate Central in their forecast system.  This gives you a flood risk map for the world in 2050 [1] and it's a lot worse than people realise.  For example the "Thames Estuary 2100" initiative [2] has similar flood risks for 2100 as Climate Central has for 2050: i.e. the risks are rising 3 times faster.

However the risk of catastrophic sea level rise is very real, even though metres are unlikely this century.  They are real because, even if the probability of ice sheet collapse this century may be low, the impact would be horrendous.  Who would fly in a plane if there was 0.1% chance of it crashing?

Worse still, the point of no return for ice sheet collapse could be passing us at this very moment.  This point is when, whatever we try to do, we cannot stop the slide towards collapse.  This is why we need to pull out all stops, especially SAI, to prevent ice sheet collapse.  Collapse could lead immediately to several metres of SLR and inevitably to total polar ice loss and 60 metres of SLR.

This sounds like bad news: but the silver lining is that judicious SAI plus judicious CDR together could return the planet to a safe, sustainable, biodiverse and productive state within 50 years or so.

Cheers, John

[1] Climate Central map for flood risk in 2050

https://coastal.climatecentral.org/map/13/0.4503/51.469/?theme=sea_level_rise&map_type=coastal_dem_comparison&basemap=roadmap&contiguous=true&elevation_model=best_available&forecast_year=2050&pathway=ssp3rcp70&percentile=p50&refresh=true&return_level=return_level_1&rl_model=coast_rp&slr_model=ipcc_2021_med 

[2] Thames Estuary 2100: Why we need it

https://www.gov.uk/guidance/thames-estuary-2100-why-we-need-it

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