California’s unused dam safety powers hold lessons for London’s ageing flood infrastructure

A California state audit has revealed that regulators have never used their enforcement powers against dam owners, despite 57 dams in poor or unsatisfactory condition and an El Niño winter approaching. The finding, reported by Cal Matters and summarised by Planetizen, raises questions about the gap between statutory authority and practical enforcement — a gap that holds direct relevance for London’s own ageing flood defence infrastructure.

The audit by the California State Auditor found that the 40 riskiest dams — rated high or extremely high hazard — cluster near densely populated coastal cities including San Diego, Los Angeles and the Bay Area. Should these dams fail, they could collectively endanger as many as 1.5 million people and cause more than $265 billion in economic damage. Engineers have notified the state of 44 dams that violate safety requirements, but the state has never taken punitive enforcement actions against dam owners who fail to remedy violations.

Key facts
| Metric | California | London (context) |
|——–|————|—————–|
| Dams/barriers in poor condition | 57 dams (poor or unsatisfactory) | Thames Barrier approaching design life; multiple tidal flood barriers need upgrade |
| People at risk in worst case | 1.5 million from dam failure | 1.3 million people in London floodplain; 500,000 properties at risk from tidal and fluvial flooding |
| Economic damage potential | $265 billion | Estimated £100 billion+ for London without Thames Barrier upgrades |
| Enforcement actions taken | Zero | UK Environment Agency has enforcement powers but has faced criticism over flood defence maintenance timelines |

The enforcement gap in California

California lawmakers gave the state the power to punish dam owners whose infrastructure violated safety requirements in 2017. Yet the audit found the power has never been used. The California State Auditor warned that dams “continue to pose a risk to public safety” as an El Niño winter looms, bringing higher rainfall and increased flood risk.

The Savage Dam in San Diego County, shown in the audit’s primary image, is one example of the ageing infrastructure at risk. The audit’s finding that the state “has never taken punitive enforcement actions against dam owners that fail to remedy their violations” points to a systemic issue: regulatory powers exist on paper but remain unused when the political or financial cost of enforcement seems high.

How this connects to London’s flood defence challenge

London’s flood defence infrastructure faces a different but structurally similar problem. The Thames Barrier, completed in 1984, was designed with a design life to 2030. The Environment Agency has been planning for its replacement or upgrade, but decisions on funding, timelines and the precise approach remain in progress. Beyond the barrier, London relies on a network of tidal flood barriers, river walls, embankments and drainage systems, much of which is ageing and requires ongoing investment.

The UK’s regulatory framework for flood defence is different — the Environment Agency, local authorities and the Greater London Authority share responsibility — but the gap between having powers and using them is familiar. The Environment Agency has enforcement powers over flood defence asset owners, including the ability to serve notices requiring maintenance or improvement. Yet critics have pointed to delays in major projects, such as the Thames Estuary 2100 plan, which has been through multiple iterations and funding reviews without a final commitment to a new barrier or alternative approach.

The London context: what is at stake

Approximately 1.3 million people live in London’s floodplain, and more than 500,000 properties are at risk from tidal and fluvial flooding. The economic damage from a major flood event in London has been estimated at well over £100 billion. The Thames Barrier has been used more frequently than originally anticipated — it was raised 221 times between 1982 and 2020, and the frequency of closures has increased as sea levels rise and storm surges become more common.

The parallels with California’s dam safety situation are not exact, but the core lesson is: regulatory authority without enforcement action is an invitation to deferred risk. In California, dam owners have been notified of violations but face no penalty for non-compliance. In London, the Environment Agency and the GLA have powers to require flood defence improvements, but the gap between what is planned and what is funded remains significant.

What London planners and residents should watch

For London’s built-environment professionals and flood-risk stakeholders, the California audit offers a practical checklist. First, the stage of decision-making: the Thames Estuary 2100 plan is still in the strategy and consultation phase, not yet in construction. Second, the enforcement question: who holds the power to compel action if flood defences are not maintained or upgraded? Third, the funding gap: the Environment Agency’s capital budget for flood defence is set through government spending reviews, and London’s share must compete with national priorities.

The London Assembly’s Environment Committee has previously raised concerns about the pace of flood defence investment, and the GLA’s London Climate Resilience Review, published in 2024, called for faster action on flood risk. But as California’s audit shows, having a plan and having the will to enforce safety standards are two different things.

Practical next steps for readers

For readers tracking this issue, the next official milestones include the next update of the Thames Estuary 2100 plan, expected from the Environment Agency in 2026, and the outcome of the government’s next spending review, which will set flood defence budgets for the following three years. London boroughs are also required to produce Local Flood Risk Management Strategies, which should detail local flood defence priorities and maintenance schedules.

The California story is a reminder that infrastructure risk is not just about engineering — it is about governance, enforcement and the willingness to use the powers that exist. For London, the question is whether the city’s flood defence plans will be backed by timely investment and, if necessary, enforcement action, or whether the gap between authority and action will persist until a crisis forces the issue.

Source: Planetizen News, “CA officials have the power to fix the state’s riskiest dams. They’ve never used it,” https://www.planetizen.com/news/2026/10/138658-ca-officials-have-power-fix-states-riskiest-dams-theyve-never-used-it

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