1001 Smart Cities
🇯🇵 Osaka

Tsunami-Alert Automatic Tide Gate Closure

🤖 AI-generated summary · ◆ 7 sourced claims · 🔎 Last verified

This overview was generated with AI from the public sources listed below and checked against them before publication. It has not had a complete human fact-check — treat it as a starting point and follow the sources.

7 sourced claims on this page, none individually verified yet — turn on “Sources in the text” to see each one.

How this atlas is made · What “last verified” means · What “source-checked” means · The full record behind this page

✎ Corrected 27 Aug 2026 Evidence grade changed: peer-reviewed → official. · 2 revisions in all What changed →

Seven gates on five rivers, closing themselves off the national tsunami alarm - the two small ones on an advisory, the big three only on a warning. About 21 square kilometres of the city sit below the sea.

Outcome🔄 Ongoing
Evidence🏛️ Officialgrades the sourcing — this entry states no impact figure
what does this mean?The strongest source is the operator's or the city's own reporting — an official report, dataset or press release. It grades who did the looking — not how well the project went. All four grades →
Run byOsaka Prefecture, Nishi-Osaka Flood Control Office
Scale🏙️ City-wide

Part of 1001 Smart Cities — 1,167 documented projects · 🏙️ 8 more in Osaka · 🌊 Flood resilience guide · 🌱 Environment projects

About 21 square kilometres of western Osaka lie below sea level after decades of industrial groundwater pumping, shielded by seven tide gates on five rivers. Osaka Prefecture's Nishi-Osaka Flood Control Office closes them automatically off the national J-Alert signal, on a threshold that differs by gate: Sangenya and Dekishima shut on a Japan Meteorological Agency tsunami advisory, the other five only on a warning. The three 1970 arch gates on the Aji, Shirinashi and Kizu rivers joined in April 2023, sounding an eight-minute warning to boats first, and are now being replaced.

Live 📅 since 2018

🎓 Lesson

Automation is possible here precisely because no judgement is involved: a Japan Meteorological Agency tsunami warning is a binary national signal, so a relay can act on it in seconds and the gate shuts without anyone deciding. What the prefecture kept for people is the cost of being wrong - the three big shipping gates close only on a warning, not on the lesser advisory, and give boats eight minutes of countdown; the two smaller ones close on an advisory and give three.

🌱 EnvironmentFlood resilienceWaterSafety & security

Sources

↗ Osaka Prefecture, Nishi-Osaka Flood Control Office — automatic tide gate closure noticeUpdated 1 April 2023The office's own notice: which alert level closes which gate, the J-Alert mechanism, and the countdown each gate runs before it shuts. The page states only a last-updated date, so no publication date is recorded.
↗ Osaka Prefecture — renewal of the three great tide gatesThe prefecture's page on replacing the three arch gates. No publication date is recorded: the page did not answer when this entry was checked.
↗ Osaka Prefecture — Osaka, a city lower than the seaOfficial source for the subsidence framing: heavy industrial groundwater extraction caused subsidence; about 21 square kilometres of western Osaka lie below sea level and about 41 square kilometres below mean high tide. No publication date is recorded: the page did not answer when this entry was checked.
↗ Osaka Prefecture — river facilities of western OsakaLists the facilities the office runs — three arch gates, other gates, 46 storm-surge steel doors and a pumping station — and names the gate remote monitoring and operation system that carries the closure commands. The page states no publication date.
↗ Mori et al., Field Survey of 2018 Typhoon Jebi in Japan, Geosciences 8(11):412Published 9 November 2018Peer-reviewed field survey of Typhoon Jebi's storm surge against the design level of Osaka's coastal defences. Publication date from Crossref. Cited here as context for the 2018 Typhoon Jebi storm surge; no statement in this entry rests on it.
Show your work What this page rests on and what it can’t tell you · all 7 claims with their sources · the forensic record

Evidence Passport · public beta 7 addressable claims, 5 source dossiers, one permanent baseline. The passport is unreviewed — an AI-assisted structural migration, not a human or expert endorsement. Every revision keeps a permanent copy under revision history.

Inspect the claims, one by one — verbatim text, sources and caveats for all 7

The text below is copied verbatim from the published record. Each claim names the source dossiers that carry it; caveats stay attached to the claim they qualify.

Claim 1 clm-48aadbfb3094c2fd quantitative
About 21 square kilometres of western Osaka lie below sea level after decades of industrial groundwater pumping
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The prefecture's own page on the area below sea level sets out the extent of the subsided zone in western Osaka and its cause in industrial groundwater extraction.
Caveat
A Japanese-language prefecture page; no locator string is recorded because the figure is presented graphically rather than in one quotable sentence.

Sources carrying this claim

  1. Osaka Prefecture — Osaka, a city lower than the sea
Claim 2 clm-e6174e22efe10a89 descriptive
shielded by seven tide gates on five rivers
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The closure notice names all seven gates - Aji, Shirinashi, Kizu, Rokkenyagawa, Shorenji, Sangenya and Dekishima - in its closure-criteria table, and the river facilities page places them on the rivers of western Osaka.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. Osaka Prefecture, Nishi-Osaka Flood Control Office — automatic tide gate closure notice
  2. Osaka Prefecture — river facilities of western Osaka
Claim 3 clm-e4906c477f8fc24c descriptive
closes them automatically off the national J-Alert signal
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The notice explains the mechanism: on a tsunami advisory or warning issued to Osaka Prefecture, the Fire and Disaster Management Agency emits the J-Alert signal, and on receiving it the office automatically sends a closure signal to each gate.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. Osaka Prefecture, Nishi-Osaka Flood Control Office — automatic tide gate closure notice
Claim 4 clm-20c033ab546426fe descriptive
Sangenya and Dekishima shut on a Japan Meteorological Agency tsunami advisory, the other five only on a warning
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The closure-criteria table gives a closure for Sangenya and Dekishima in the tsunami-advisory column as well as the warning columns, while the Aji, Shirinashi, Kizu, Rokkenyagawa and Shorenji rows are blank in the advisory column and closed only from the warning column onwards.
Caveat
The atlas previously said any advisory or warning closed every gate. The prefecture's own table shows the threshold differs by gate.

Sources carrying this claim

  1. Osaka Prefecture, Nishi-Osaka Flood Control Office — automatic tide gate closure notice
Claim 5 clm-5d1553034a5f7596 quantitative
The three 1970 arch gates on the Aji, Shirinashi and Kizu rivers joined in April 2023, sounding an eight-minute warning to boats first, and are now being replaced
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The notice lists the start of automatic operation by gate - April of Reiwa 5, that is 2023, for Aji, Shirinashi and Kizu - and states that those three warn for eight minutes after receiving the closure signal before shutting. The renewal page covers their replacement.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. Osaka Prefecture, Nishi-Osaka Flood Control Office — automatic tide gate closure notice
  2. Osaka Prefecture — renewal of the three great tide gates
Claim 6 clm-3756af1200d045d1 descriptive
a Japan Meteorological Agency tsunami warning is a binary national signal, so a relay can act on it in seconds and the gate shuts without anyone deciding
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The notice describes exactly this chain and nothing else in it: the meteorological agency issues the warning, the Fire and Disaster Management Agency emits J-Alert, the office's system receives it and sends the closure signal to each gate automatically. No human decision appears anywhere between the alert and the gate.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. Osaka Prefecture, Nishi-Osaka Flood Control Office — automatic tide gate closure notice
Claim 7 clm-da2d2ee56bac5e05 descriptive
the three big shipping gates close only on a warning, not on the lesser advisory, and give boats eight minutes of countdown; the two smaller ones close on an advisory and give three
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The notice sets both out: the criteria table shows the advisory column closing only Sangenya and Dekishima, and the text states 'Aji, Shirinashi and Kizu warn for 8 minutes after receiving the closure signal; Rokkenyagawa, Shorenji, Sangenya and Dekishima warn for 3 minutes, after which the gates close.'
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. Osaka Prefecture, Nishi-Osaka Flood Control Office — automatic tide gate closure notice
Forensic record — source dossiers, gaps, hashes and the exact revision this page renders

This layer records what is known about each source, what is still missing, and the exact snapshot this page is rendering. A missing date, archive or hash stays visible as missing.

unreviewed Revision 2026-08-27-editorial-review effective 2026-08-26 · created 2026-08-27

Awaiting operator and domain-expert review; publication of this revision implies neither.

sha256:6ced757fe7c9ffa3e61e9dd158f937b71a131266c372f59a5c07b61b01be7322
Revision history → Permanent version link → Machine-readable record → Evidence Constitution →
7
of 7 claims mapped
5
source dossiers
1
publication dates recorded
0
archives linked
0
exact locators
0
content captures hashed

Governance facts carried by the record

Operator
Osaka Prefecture, Nishi-Osaka Flood Control Office
Actor types
regional-government
Funding model
public
Funding description
Not recorded
Cost
Not recorded
Ownership
Not recorded
Decision rights
Not recorded
Exit conditions
Not recorded

5 source dossiers

Osaka Prefecture, Nishi-Osaka Flood Control Office — automatic tide gate closure notice pref.osaka.lg.jp · 6 linked claims

Open original source ↗

Stable source ID
src-f7064087841a71e4
Publisher
Name not classified · pref.osaka.lg.jp
Type / language
web-page · language not classified
Published
Not recorded
Updated
2023-04-01
Source last checked
No source-level check date
Record last verified
2026-08-26
Dossier created
2026-08-27
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

The office's own notice: which alert level closes which gate, the J-Alert mechanism, and the countdown each gate runs before it shuts. The page states only a last-updated date, so no publication date is recorded.

Descriptive only — not page/paragraph exact
Claims linked
Osaka Prefecture — renewal of the three great tide gates pref.osaka.lg.jp · 1 linked claim

Open original source ↗

Stable source ID
src-f156e54486e97917
Publisher
Name not classified · pref.osaka.lg.jp
Type / language
web-page · language not classified
Published
Not recorded
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-26
Dossier created
2026-08-27
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

The prefecture's page on replacing the three arch gates. No publication date is recorded: the page did not answer when this entry was checked.

Descriptive only — not page/paragraph exact
Claims linked
Osaka Prefecture — Osaka, a city lower than the sea pref.osaka.lg.jp · 1 linked claim

Open original source ↗

Stable source ID
src-48cff65ee8b7f92e
Publisher
Name not classified · pref.osaka.lg.jp
Type / language
web-page · language not classified
Published
Not recorded
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-26
Dossier created
2026-08-27
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Official source for the subsidence framing: heavy industrial groundwater extraction caused subsidence; about 21 square kilometres of western Osaka lie below sea level and about 41 square kilometres below mean high tide. No publication date is recorded: the page did not answer when this entry was checked.

Descriptive only — not page/paragraph exact
Claims linked
Osaka Prefecture — river facilities of western Osaka pref.osaka.lg.jp · 1 linked claim

Open original source ↗

Stable source ID
src-7fbe387f3963d155
Publisher
Name not classified · pref.osaka.lg.jp
Type / language
web-page · language not classified
Published
Not recorded
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-26
Dossier created
2026-08-27
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Lists the facilities the office runs — three arch gates, other gates, 46 storm-surge steel doors and a pumping station — and names the gate remote monitoring and operation system that carries the closure commands. The page states no publication date.

Descriptive only — not page/paragraph exact
Claims linked
Mori et al., Field Survey of 2018 Typhoon Jebi in Japan, Geosciences 8(11):412 mdpi.com · background

Open original source ↗

Stable source ID
src-72d10f810611e1b8
Publisher
Name not classified · mdpi.com
Type / language
web-page · language not classified
Published
2018-11-09
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-26
Dossier created
2026-08-27
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Peer-reviewed field survey of Typhoon Jebi's storm surge against the design level of Osaka's coastal defences. Publication date from Crossref. Cited here as context for the 2018 Typhoon Jebi storm surge; no statement in this entry rests on it.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
Known limits of this passport
  • Publisher names and source languages have not yet been classified; domains are recorded without guessing.
  • Existing source notes are descriptive locators, not page- or paragraph-exact citations.
  • A missing archive, publication date or content hash is shown as null rather than inferred.
  • The project-level evidence grade ranks the strongest source in the entry; it is not a truth score for every claim.

Continue exploring

Compare this project

🇹🇷 Earthquake Early Warning & Seismic Monitoring Network · Istanbul Sensors that pull levers, not just alarms: Istanbul's seismic net halts trains and gas; a tsunami alert closes seven Osaka tide gates. 🇩🇰 Copenhagen's Cloudburst Management Plan · Copenhagen Two ways to keep water out: Copenhagen rebuilt streets and parks to hold rain; Osaka shuts steel gates on the national alert signal. 🇺🇸 Miami Forever flood-resilience program · Miami Both defend ground below the sea: Miami builds pumps and seawalls; Osaka's 21 km² of sunken land sits behind seven automatic tide gates.

When the river rises: what is the reading allowed to do?

Four flood systems, four answers to the question that organises much of this atlas — whether a measurement triggers anything. The ladder runs from a reading that acts entirely by itself down to a network that watches everything and decides nothing.

ProjectSinceStatusOutcomeEvidenceRun byCostWhat the reading may do
Tsunami-Alert Automatic Tide Gate ClosureOsaka, 🇯🇵 2018 Live Ongoing Official Regional government not public The reading acts by itself: the tide gates close automatically on the national alert, with no human in the loop.
Bangkok Flood Control Centre: Drainage Telemetry & Street-Level ForecastingBangkok, 🇹🇭 2021 Live Ongoing Official City government, Utility or public operator not public Staff decide with the data: radars and level sensors feed a control centre staffed around the clock, and crews operate the pumps.
Busan Urban Flood Warning System (Busan Safety ON)Busan, 🇰🇷 2023 Live Ongoing Official City government not public Warning only: the portal shows risk and alerts residents, and the city itself cautioned at launch that the readings could be wrong.
SIATA Early Warning NetworkMedellín, 🇨🇴 2010 Live Ongoing Media Research institution not public A research-run regional network that watches everything — including, once, a fatal flash flood in real time that no agency acted on.

Explore the wider context

📟 A Reading Is Not a Decision📖 Flood early-warning system📖 ANPR (automatic number-plate recognition)📖 Automated speed enforcement (speed cameras)
📎 Cite this project

1001 Smart Cities (2026). “Tsunami-Alert Automatic Tide Gate Closure” — Osaka, Japan. The Smart City Atlas. https://1001smartcities.org/projects/osaka-tide-gate-auto-closure/ (last verified 2026-08-26). Data: CC BY 4.0.

The underlying data is free to reuse with attribution — see the open data page.

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