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Flood risk in the Square Mile

Hands holding umbrellas

The City of London Corporation is working to ensure the City stays at low risk from flooding.

What are the risks of flooding?

There are relatively small areas of the City which are at risk of flooding. However, it is vital to know about the risk that your property may face in order to understand how to prepare for it.

The City of London Strategic Flood Risk Assessment (2017) provides the most up-to-date information on the risks the City faces from tidal, surface water, sewer and groundwater flooding. You will find maps which show where the City's flood risks are in the Appendices.

Surface water flooding is one of the City's high risks. Surface water maps showing the flooding depths are available in the SFRA maps list.

Contact us

If you have any questions or would like any further information email the Sustainability Team.

How do I keep informed?

Business continuity

Business continuity is the capability of your organisation to continue to deliver its products or services following a disruptive incident. Robust business continuity arrangements are essential for businesses of any size - devising strategies to protect your key products, services and critical activities will enable you to trade through a disruption and recover promptly afterwards. The City of London's Contingency Planning Unit can support you in developing and exercising your business continuity arrangements. There is no charge for these services for organisations based within the City of London.

Floodline Warning Direct

Floodline Warning Direct is a free 24 hour flood warning service, provided by the Environment Agency, where individuals can register their properties. You are encouraged to sign up for this service. You can opt to receive a warning by telephone, text or email.

Keep up to date with current alerts and warnings

Use a combination of the sites below to provide weather warnings and flood alerts. These services can provide enough time for temporary flood protection measures to be put in place. In the event of a possible flooding incident, the Environment Agency and the Met Office provide a suite of services to communicate forecasts and broadcast up-to-date information to the public. These include the following:

Environment Agency

Met Office

The National severe weather warnings page, part of the Met Office website provides detailed information and navigates the user to other useful information provides detailed information and navigates the user to other useful information. The Weather Observation Website (WOW) is part of the Met Office site and is a hub for UK weather observations. This service allows anyone to submit their own weather data, anywhere in the world. These observations are a source of real-time information.

Your local media

When the situation becomes a cause of concern for ground, property and life, flood alerts and warnings will be broadcasted on local media (television, radio and the internet).


The City of London will use Twitter to provide information to the public, follow:

How is the City Corporation protecting the City?

The City of London Corporation, as Lead Local Flood Authority coordinates the actions to address flood risk in the City, including:

  • the preparation of a local flood risk management strategy
  • the investigation and reporting on flooding incidents
  • the maintenance of a register of flood prevention assets
  • and acting as "approving body" with regard to surface water drainage

Documents prepared by the City of London to report on the flood risk in the City are as follows:

The City of London Strategic Flood Risk Assessment (2017) provides the most up-to-date information regarding the risks the City faces from tidal, surface water, sewer and groundwater flooding. In the SFRA maps list you will find maps which show the flood risk in the City.

The City of London Local Flood Risk Management Strategy 2014-2020 (LFRMS) (1MB) details the flood risks that the City faces, including flooding from the tidal River Thames, surface water and sewer surcharges and rising groundwater. As a Lead Local Flood Authority, the City of London has the responsibility to develop, maintain, apply and monitor strategy for local flood risk management in the area. The LFRMS includes a Flood Risk Action Plan which identifies the practical steps that the City Corporation and other partners need to take to reduce their risks from flooding.

Reports on a Strategic Environmental Assessment (2MB) and an Equality Impact Assessment (600KB), and a public consultation have informed the LFRMS.

The Multi Agency Flood Plan covers the background and procedures for a multi-agency response to a flood incident in the City of London.​

The City of London's Flood Risk Asset Register is a list of structures that we consider are likely to have a significant effect on flood risk. The register provides a resource to assist in flood resilience planning and aid investigation following a flooding incident.

The City Corporation has produced briefing notes for individual properties in the flood risk area - please see the Flood Risk Map to access them. These documents outline the flood risk to a particular property and the planning policy that relates to flood risk in the area.

The Flood Risk Map also shows locations where the City Corporation has completed a flood investigation and has issued a report. Investigations are carried out where more than one property is affected by a single source of flooding. For copies of these flood investigation reports please email the Sustainability Team quoting the location and date of the flood.

Guidance for businesses and property owners

Flooding can have an impact on the ability of businesses within the City to operate effectively, even when it occurs beyond the Square Mile. The City has prepared guidance notes to advise City occupiers on steps they could take to help reduce the impact of flooding on them.

For businesses, see our guide Staying afloat in the Square Mile (487KB) and for property owners, see our guide Out of your depth in the Square Mile (487KB). In some cases both guides will be appropriate.

More information