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From individual development plots to strategic allocations, we help clients understand flood risk and drainage early and turn it into practical, deliverable solutions.
We support developers, landowners, promoters, planning consultants, local authorities and multidisciplinary project teams on residential, commercial, employment and mixed-use developments of all scales. Our specialist services include flood risk assessments, hydraulic modelling, drainage strategies, Sustainable Drainage Systems (SuDS) design, nutrient neutrality support, regulatory engagement and detailed drainage design.
Why Choose Brookbanks for Hydrology
Early involvement allows us to identify the hydrological considerations that may influence site selection, masterplanning, infrastructure requirements, development viability and delivery programmes. As projects progress, we work collaboratively with clients and project teams to develop proportionate, practical solutions that satisfy planning and regulatory requirements while supporting wider project objectives.
Our experts have extensive experience working with the Environment Agency, Natural Resources Wales, Internal Drainage Boards, Lead Local Flood Authorities, SuDS Approval Bodies and water companies. We understand the technical evidence required to support applications and address regulatory concerns.
Combining technical expertise with an understanding of planning, development economics and project delivery, we help clients make informed decisions and move proposals forward with confidence. In-house hydraulic modelling lets us test flood risk and drainage solutions in detail, and our experience in areas such as nutrient neutrality helps clients respond to evolving regulatory requirements.
Key Client Benefits
- Identify constraints early – understand flood risk and drainage implications before committing to land, layout and programme decisions.
- Balance technical and commercial priorities – develop practical solutions that address regulatory requirements while considering development viability.
- Navigate regulatory requirements – draw on our experience with regulators and approving bodies to inform submissions and support constructive discussions.
- Maintain continuity throughout the project – access coordinated support from initial site appraisal and pre-application advice through to detailed drainage design and discharge of planning conditions.
- Address nutrient neutrality requirements – understand site-specific constraints and assess potential mitigation options in sensitive catchments.
- Integrate drainage with landscape design – explore opportunities for blue-green spaces that support biodiversity, wellbeing and a stronger sense of place.
Specialist Services
Flood Risk Assessment and Hydraulic Modelling
Flood risk can shape site design, development proposals and planning decisions. We prepare assessments in accordance with the relevant national planning policy and guidance in England and Wales.
Requirements differ either side of the border, so we work under the National Planning Policy Framework (NPPF) and Planning Practice Guidance (PPG) in England and Technical Advice Note 15 (TAN15) in Wales.
Detailed hydraulic modelling and watercourse analysis give a clearer understanding of flood behaviour and how a development interacts with the surrounding water environment. Our specialists build and run one-dimensional (1D) and two-dimensional (2D) models to assess flood extents, flow routes, depths and water levels under a range of scenarios, including the effects of proposed development and mitigation. The results inform Flood Risk Assessments, drainage strategies, site design and finished floor levels.
See how our specialists resolved a flooding constraint at Wixam Park.
Drainage Strategies and Detailed Drainage Design
A well-prepared drainage strategy sets out how surface water and foul drainage will be managed and forms an important part of any planning application. At outline stage, our strategies establish the drainage principles and show that a viable, cost-effective solution exists within the constraints of the site. Wherever possible, we engage early with drainage authorities and sewerage undertakers to agree the approach before submission.
From planning approval through to construction, our team designs surface water and foul drainage networks, attenuation features, pumping stations and outfall structures, supported by detailed calculations, specifications and construction information. Designs are coordinated closely with ground conditions, site levels and the wider design team, and we continue to support the project during delivery to resolve design queries.
Read how we refined the drainage and levels strategy at Hawthorn Corner in Whitstable.
Sustainable Drainage Systems (SuDS) Strategy and Design
Sustainable Drainage Systems manage surface water effectively while supporting water quality, biodiversity and amenity. Well-designed SuDS can create attractive, multifunctional spaces that raise the overall quality of a scheme.
Our specialists prepare SuDS strategies and detailed designs across a range of sectors and scales, considering site characteristics, planning requirements and long-term maintenance from the start. Green roofs, permeable paving, swales, detention basins, wetlands, attenuation systems and other green infrastructure are coordinated with the wider design team so that each solution is practical, cost-effective and buildable.
Explore our 2026 report on SuDS challenges and solutions.
Nutrient Neutrality Assessments and Mitigation
Nutrient neutrality is an important consideration in a number of protected river and estuary catchments across England and Wales, where proposals must show that additional nutrient loading will not adversely affect protected habitats.
Our hydrology and nutrients specialists work together, we help clients understand the requirements, assess potential impacts and develop appropriate mitigation. This covers nutrient budget calculations, mitigation strategy development, habitat and wetland feasibility studies, drainage and SuDS design, and engagement with Natural England, Natural Resources Wales and other consultees.
Regulatory Liaison and Expert Witness Support
Early dialogue with regulators, statutory consultees and infrastructure providers brings clarity on technical requirements and often supports a more efficient planning process. On our clients’ behalf, we engage regularly with the Environment Agency, Natural Resources Wales, Internal Drainage Boards, sewerage undertakers, Lead Local Flood Authorities and SuDS Approval Bodies, coordinating pre-application discussions, preparing supporting information and working towards agreed positions before applications are submitted.
Hydrology, drainage and flood risk matters can also form an important part of planning appeals, Public Inquiries and legal proceedings. Our hydrology experts prepare proofs of evidence, rebuttal statements, technical reviews and statements of common ground, presenting complex information clearly to Inspectors, Examining Authorities and the courts. At the pre-inquiry stage, they can also advise on the strength of drainage and flood risk evidence and help shape the wider appeal strategy.
Sectors We Support
We provide hydrology, flood risk and drainage services for residential, commercial, employment and mixed-use developments across England and Wales.
Our clients include developers, landowners, promoters, planning consultants, local authorities and multidisciplinary project teams.
We support projects ranging from individual plots to strategic allocations and major development sites. Our involvement can cover a specific task, such as discharging a drainage-related planning condition, or extend from initial site appraisal through to detailed design and construction support.
Talk to Our Hydrology Specialists
If you are appraising a new site, preparing a planning application or designing drainage for delivery, contact a member of the team directly, or email hello@brookbanks.com and one of our experts will get back to you.
Group Technical Director, Land, Development and Communities
Dean Swann
dean.swann@brookbanks.com
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Pauline Lokidor
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FAQs
When does my site need a Flood Risk Assessment?
A Flood Risk Assessment is usually required where a site lies within an area at risk of flooding, or where a development exceeds certain size thresholds. The exact requirements depend on national policy in England or Wales and on local planning policy. Our specialists can review your site early and confirm what level of assessment is needed.
What are the Sequential and Exception Tests?
They are planning policy tests used to steer development towards areas at lower risk of flooding. The Sequential Test considers whether reasonably available sites at lower risk exist. The Exception Test, where it applies, considers whether a development can be made safe for its lifetime and deliver wider benefits, and we prepare the evidence needed to support both.
At what stage should we involve your hydrology specialists?
As early as possible. Input at site appraisal or acquisition stage allows flood risk and drainage considerations to inform masterplanning, layout and viability. We are equally happy to support a single assessment, a planning condition or a detailed design package at a later stage.
Can you take drainage from strategy through to construction?
Yes. We prepare drainage strategies for outline and detailed applications and then develop them into detailed surface water and foul drainage designs. This gives continuity from planning through to delivery.