Flood Investigation & Management Strategy

A Flood Investigation & Management Strategy is a bespoke, engineering-led commission for sites where a standard Flood Survey cannot provide sufficient technical certainty.

The work may include detailed site inspection, review of drainage and wider catchment interactions, ground conditions, existing infrastructure and available datasets to identify flood pathways, constraints and realistic management options. This often moves beyond property-level measures to consider site levels, flow routes, surface water drainage, SuDS, wider civil engineering interventions or future development.

The outcome is an evidence-based understanding of the mechanism and a defined, proportionate route towards implementation.

The findings from a Flood Investigation often progress to Options Development and Design, where mitigation measures such as drainage improvements, flood walls or storage are designed.

Typical commissions are prompted by a real problem. A property that has flooded more than once and the question is whether to invest in resilience, alteration or rebuilding. A site where water now ponds or flows differently and there is pressure to install a solution before anyone has confirmed where it actually goes.

It is most relevant where the response may involve changes to levels, drainage, flow routes or buried infrastructure, or where proposed works need to be tested against the actual flood behaviour of the site. The first stage is to establish what is known, what is not and what level of investigation is required before moving towards design.

This route is chosen where a standard Flood Survey would not provide enough certainty for the decision being made and the response starts to move into civil engineering rather than reporting. That may be because levels need to change, flow routes need to be managed, drainage infrastructure needs to be altered, or future development has to be tested against the actual flood behaviour of the site. The work establishes a defensible technical position that can be relied upon for planning, investment and detailed design.

It is typically commissioned where a proportionate but significant investment in understanding or managing flood risk is justified.

FPS Environmental was commissioned to review a commercial site in Leicestershire experiencing surface water flooding where the building was a portal frame structure. Conventional property-flood resistance (PFR) was not a realistic option without significant alteration to the building fabric. The investigation considered the wider site and identified that unused grassland could form part of a SuDS-based approach, providing both attenuation and amenity benefit and, over time, influencing the mapped surface water risk. The study defined the next stages, which included CCTV survey and hydraulic modelling. Those works were subsequently undertaken and resulted in a modelled and deliverable site wide mitigation strategy, which was subsequently taken forward to detailed design.

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FPS Environmental was commissioned to undertake climate-change flood stress testing across a high-value central London estate comprising mixed commercial, hospitality and residential assets. The work moved beyond national mapping to understand how each building would perform during an extreme rainfall event, through detailed walkovers, drainage appraisal and engagement with site teams.

The study identified that the principal risk was not predicted flood depth but the absence of verified asset and drainage information. By stress testing pump failure, sewer surcharge and threshold exceedance scenarios, we provided a prioritised programme for operational improvement, capital investment and the implementation of a centralised BIM-based asset management system. This created a clear and defensible pathway for resilience, business continuity and future refurbishment planning.

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