What is a Section 19 flood investigation?

The 2023/24 storm season saw the most named weather events since 2015, according to the Met Office. Many of these led to flooding that affected homes and businesses across the UK. 

Under Section 19 (S19) of the Flood and Water Management Act 2010, lead local flood authorities (LLFA) are required to investigate flood incidents, where necessary. Whether or not an investigation is needed is based on the specific criteria set out within the LLFA’s risk management strategy. 

How to determine if a S19 investigation is required

The LLFA will determine if an event is significant enough to require a S19 investigation based on the following criteria:

Properties affected — If ten or more properties in a river catchment experience internal flooding, or five or more residential properties are internally flooded in a single event

Critical infrastructure  — If one or more items of critical national infrastructure experience flooding 

Transport links — If a transport link is impassable for a number of hours 

Repeat flooding — If a single property experiences repeat internal flooding within five years 

Elected member request — If an elected member requests a Section 19 Flood Investigation

No other risk management authority — If no other risk management authority is exercising or proposing to exercise its risk management functions 

What does a S19 flood report involve?

The structure of a S19 flood investigation depends on the LLFA’s requirements. In general, it examines the causes and impacts of the flood event, identifies responsible parties, and allows for appropriate measures to be implemented to mitigate future risks. This requires:

• Site inspection

Consultants will visit reported flood locations to gather data on drainage, watercourses, and topography. They will interview property owners and residents to understand the flooding’s impact, often using a standard questionnaire. If residents are unavailable, questionnaires are left for later responses.

• Data collection

The team reviews drainage information and conditions, recent weather patterns, and the pre-flood situation of a site to create a pre-flooding baseline environment.

• Flooding mechanism analysis

Based on photographic evidence, discussions with residents, and site visits, the likely cause of flooding (pluvial, fluvial, groundwater, etc.) is identified.

• Reporting

The investigation is summarised in each report, including the flooding mechanisms, causes, and conditions prior to the event.

• Recommendations

The report outlines mitigation measures to help prevent damages from future flooding and provides guidance as to whether the area is suitable for a capital project. Relevant risk management authorities (RMAs) are identified based on their flood risk management roles.

The LLFA will publish the document on their website, whether as a whole, or on individual areas, although it is the LLFA’s decision how they conduct this. Some will publish an investigation once per year, analysing any and all flood events that occurred over that period. 

Who can produce a Section 19 Flood Report?

Some LLFAs conduct investigations in-house. When required, this is supported by environmental consultancies with relevant experience – GeoSmart has undertaken a number of investigations in the most recent storm year.

How can GeoSmart help you?

GeoSmart uses our own innovative flood risk software FloodSmart Analytics to calculate flood risk and flood depths from multiple types of flooding that includes groundwater (a vital source of flooding which is often disregarded) for the whole of the UK.

GeoSmart has been providing flood risk assessments and consultancy since our inception in 2013, supporting local authorities, planning consultants, developers, architects, surveyors, project managers and insurance and finance professionals.

GeoSmart employs an expert team of hydrologists, geologists and hydrogeologists who hold chartered status with relevant professional bodies including CIWEM and the Geological Society.

GeoSmart also provides a UK groundwater flood risk map and data which is used in around 33% of all UK property transactions annually.

If you are a Local Lead Flood Authority and need help with your S19 investigation, please contact us today to discuss your requirements:

Ben Mowl, Sales Manager – 01743 298 096

Martin Lucass, Commercial Director – 07494 852 498