Flood Risk Assessment Edinburgh

Flood Risk Assessment Services in Edinburgh

Edinburgh’s position between the Firth of Forth coastline and the Pentland Hills creates a diverse and challenging flood risk landscape. With the Water of Leith, Braid Burn, and numerous smaller watercourses threading through the city, developers must navigate a complex regulatory environment governed by SEPA, NPF4, and the City of Edinburgh Council’s local planning policies.

Aegaea provides specialist flood risk assessment and drainage consultancy services across Edinburgh, supporting residential, commercial, and mixed-use developments from initial feasibility through to planning approval and construction. Our team holds detailed knowledge of Edinburgh’s watercourse systems, SEPA flood maps, and the local planning authority’s specific requirements for flood risk documentation.

Understanding Edinburgh’s Flood Risk Landscape

The Water of Leith

The Water of Leith is Edinburgh’s principal river, rising in the Pentland Hills near Balerno and flowing approximately 24 kilometres through the heart of the city before discharging into the Firth of Forth at Leith Docks. The river passes through some of Edinburgh’s most sought-after development areas, including Colinton, Slateford, Gorgie, Roseburn, Murrayfield, Dean Village, Stockbridge, Canonmills, and Leith.

The Water of Leith Flood Prevention Scheme, completed in 2014 at a cost of approximately 80 million pounds, provides protection to around 3,500 properties against a 1 in 200 year flood event (0.5% annual probability). The scheme includes raised flood walls, embankments, and flow control structures at locations including Murrayfield, Roseburn, Coltbridge, and Stockbridge. However, protection standards do not eliminate flood risk entirely, and development proposals within the defended area still require careful assessment of residual risk, including the consequences of defence overtopping or failure.

Areas upstream and downstream of the defended reaches remain at risk. Sites in Balerno, Juniper Green, and Colinton may be affected by undefended fluvial flooding, while the lower reaches around Leith and the Shore face combined fluvial and tidal influences from the Firth of Forth.

The Braid Burn and Jordan Burn

The Braid Burn rises on the northern slopes of the Pentland Hills and flows through the southern suburbs of Edinburgh, passing through the Hermitage of Braid, Morningside, and Liberton before continuing eastward through Craigmillar and Niddrie to join the Figgate Burn near Portobello. The Jordan Burn, a tributary joining near Liberton, adds to the catchment complexity.

Historic flooding along the Braid Burn has caused significant damage, most notably in August 2012 when intense rainfall overwhelmed channel capacity and caused widespread surface water flooding in the Morningside and Cameron Toll areas. This event underscored the interaction between fluvial and pluvial flooding in Edinburgh’s southern suburbs, where Victorian-era combined sewers have limited capacity to manage extreme rainfall.

Development along the Braid Burn corridor requires detailed hydraulic assessment to understand flood extents under current and climate change scenarios. SEPA’s flood maps provide a starting point, but site-specific modelling is frequently required to demonstrate that proposals will not increase risk to neighbouring properties.

Coastal and Tidal Flood Risk

Edinburgh’s northern boundary along the Firth of Forth exposes substantial areas to coastal and tidal flood risk. The waterfront regeneration areas at Granton, Western Harbour, Leith Docks, and Portobello have seen intensive development pressure in recent years, and coastal flood risk is a defining constraint for these locations.

SEPA’s coastal flood maps identify extensive areas at risk from a 1 in 200 year event along the Leith and Granton waterfronts. Finished floor levels for new developments in these areas must be set above the predicted 1 in 200 year still water level plus an appropriate freeboard allowance, accounting for climate change over the development’s design life. Wave action and wave overtopping may also need to be considered for exposed coastal sites.

The Edinburgh Waterfront development framework, covering the Granton and Western Harbour masterplan areas, includes specific flood risk requirements that reflect the coastal setting. Developers working in these locations need to demonstrate compliance with both SEPA requirements and the council’s supplementary guidance on waterfront development.

Surface Water and Sewer Flooding

Surface water flooding represents a significant and growing risk across Edinburgh. The city’s topography, with steep hills draining to relatively narrow valley corridors, creates natural flow paths that concentrate surface water during intense rainfall. Combined sewer systems in the city centre and older suburbs have limited capacity, and sewer flooding has affected areas including Murrayfield, Colinton, Corstorphine, and Duddingston.

SEPA’s surface water flood maps show widespread areas at risk across Edinburgh, including locations well away from identified watercourses. The August 2012 event demonstrated that surface water flooding can be the dominant risk for many Edinburgh sites, and planning applicants must assess this risk even where fluvial flooding is not a concern.

Scottish Water’s requirements for surface water connections mean that all new developments must attenuate runoff to greenfield rates, typically using SuDS, before discharging to the public sewer network. Where infiltration is feasible, it is preferred, but Edinburgh’s geology, dominated by glacial till and mudstone in many areas, often limits infiltration capacity.

The Scottish Regulatory Framework

SEPA and the Flood Risk Management (Scotland) Act 2009

Flood risk management in Scotland differs fundamentally from the approach in England and Wales. The Flood Risk Management (Scotland) Act 2009 established SEPA as the lead authority for strategic flood risk management, with local authorities taking responsibility for local flood risk management as “responsible authorities.”

SEPA provides flood risk information through its online flood maps, responds to planning consultations on flood risk matters, and publishes guidance on flood risk assessment requirements. SEPA’s role as a statutory consultee means that its position on flood risk carries significant weight in planning decisions. Where SEPA objects to a planning application on flood risk grounds, the local authority will typically refuse the application unless the objection can be resolved.

For Edinburgh developments, SEPA’s consultation response will assess whether the submitted FRA adequately addresses all relevant flood risks, demonstrates that the development will not increase flood risk elsewhere, and proposes appropriate mitigation measures. SEPA expects FRAs to be prepared in accordance with its technical guidance documents, including the SEPA Technical Flood Risk Guidance for Stakeholders.

NPF4 Policy 22: Flood Risk and Water Management

National Planning Framework 4, adopted in February 2023, replaced the previous system of Scottish Planning Policy (SPP) and Strategic Development Plans. NPF4 Policy 22 sets out the national planning policy on flood risk and water management.

Policy 22 establishes a precautionary approach to flood risk in the planning system. Development proposals on land identified as being at risk of flooding, or which would increase flood risk elsewhere, will not be supported unless they are for essential infrastructure where no suitable alternative site is available. The policy applies to all sources of flooding, including fluvial, coastal, surface water, groundwater, and sewer flooding.

Key differences from England’s NPPF framework include the absence of a formal Sequential Test procedure (though the principle of avoiding flood risk areas is embedded in policy), the use of a 1 in 200 year design standard rather than 1 in 100 year, and the requirement for developments to account for a 0.5% annual probability event plus climate change. Scotland’s climate change allowances also differ from those applied in England, reflecting Scottish Government projections.

Edinburgh Local Development Plan

The City of Edinburgh Council’s Local Development Plan and associated supplementary guidance contain specific policies on flood risk and surface water management. Policy Env 21 (Flood Protection) and the Edinburgh Design Guidance set out detailed requirements for flood risk assessment, finished floor levels, land raising, and SuDS provision.

The council’s Strategic Flood Risk Assessment informs the spatial strategy of the local plan and identifies areas where flood risk is a significant constraint on development. Sites allocated for development in the local plan have been subject to strategic flood risk screening, but site-specific FRAs remain necessary to address detailed design matters.

What a Flood Risk Assessment in Edinburgh Involves

Desktop Assessment

A desktop FRA for an Edinburgh site will typically review SEPA flood maps (fluvial, coastal, and surface water), historic flood records held by the City of Edinburgh Council, Scottish Water sewer flooding records, OS mapping and topographic data, geology and hydrogeology information from BGS, and any relevant previous studies including the council’s SFRA and catchment flood management plans.

For lower-risk sites in Flood Zone 1 equivalent areas (little or no risk on SEPA maps), a well-evidenced desktop assessment may be sufficient to satisfy planning requirements. However, where surface water risk is identified, or where the site is close to a watercourse, further assessment is likely to be required.

Detailed Flood Risk Assessment

A detailed FRA for an Edinburgh site at medium or high flood risk will build on the desktop assessment with site-specific analysis. This may include detailed topographic survey to establish ground levels relative to Ordnance Datum, hydraulic modelling of relevant watercourses (the Water of Leith, Braid Burn, or smaller ordinary watercourses), assessment of surface water flow paths using LiDAR data and detailed DTMs, and analysis of climate change impacts using SEPA’s recommended allowances.

The assessment must demonstrate that the proposed development is safe over its lifetime, that it will not increase flood risk elsewhere, and that an appropriate range of flood mitigation measures has been incorporated. For residential developments, this includes setting finished floor levels above the 1 in 200 year flood level plus freeboard, providing safe access and egress, and incorporating property-level resilience measures where appropriate.

Drainage Strategy and SuDS Design

All Edinburgh developments require a surface water drainage strategy that satisfies Scottish Water’s requirements under Sewers for Scotland and the council’s Edinburgh Design Guidance. The strategy must demonstrate that surface water runoff will be managed through a SuDS management train, typically incorporating source control (green roofs, permeable paving, rain gardens), site control (swales, detention basins), and regional control (ponds, wetlands) where appropriate.

Scottish Water will not accept new surface water connections to the combined sewer network, and direct connections to the separate surface water sewer are only permitted after SuDS treatment. Where feasible, discharge to watercourse or ground via infiltration is preferred.

Key Development Areas and Flood Risk Considerations

Granton Waterfront

The Granton Waterfront regeneration area represents one of Edinburgh’s largest development opportunities, with plans for thousands of new homes alongside commercial, cultural, and community uses. The site’s coastal location means that flood risk from the Firth of Forth is a primary constraint. Developers must address coastal flood risk including wave action, set floor levels appropriately, and consider the long-term implications of sea level rise over the development’s design life.

Leith and the Shore

The Leith area, centred on the historic Shore district and Leith Docks, faces combined fluvial and tidal risk from the Water of Leith and the Firth of Forth. The tidal influence extends upstream along the Water of Leith, and development proposals must account for the interaction between river flows and tidal conditions. The area’s heritage character adds further complexity, as flood mitigation measures must be sensitive to the conservation area designation.

South Edinburgh Growth Corridor

Development sites along the A720 City Bypass corridor in south Edinburgh, including areas around Gilmerton, Liberton, and Burdiehouse, may be affected by the Braid Burn, Burdiehouse Burn, and associated surface water flood risk. These sites often involve greenfield land, and drainage strategies must demonstrate that development will not increase downstream flood risk in already-vulnerable suburban areas.

City Centre and Old Town

Development and change-of-use applications within Edinburgh’s city centre face particular challenges related to surface water management. The constrained urban fabric, combined sewers, and limited space for SuDS mean that innovative drainage solutions are often required. Proposals for basement conversions or below-ground development must address groundwater and surface water ingress risk, and the World Heritage Site designation adds heritage constraints to any external flood mitigation measures.

Why Choose Aegaea for Edinburgh Flood Risk Assessments

Aegaea combines deep expertise in Scottish flood risk regulation with practical experience delivering FRAs across Edinburgh. Our team understands the specific requirements of SEPA, the City of Edinburgh Council, and Scottish Water, and we maintain strong working relationships with these organisations.

We have delivered flood risk assessments for sites ranging from individual house plots to major waterfront regeneration projects across Edinburgh. Our in-house hydraulic modelling capability means we can provide detailed analysis of the Water of Leith, Braid Burn, and coastal flood risk where site-specific modelling is required.

Our Edinburgh services include desktop and detailed flood risk assessments for planning applications, hydraulic modelling of fluvial and coastal flood risk, surface water drainage strategies and SuDS design, SEPA pre-application consultation support, and expert witness services for planning appeals. We work with developers, architects, and planning consultants across Edinburgh to deliver robust, SEPA-compliant flood risk documentation that supports successful planning outcomes.

Get in Touch

If you are planning a development in Edinburgh and need a flood risk assessment, drainage strategy, or SuDS design, contact Aegaea for a no-obligation discussion. We can advise on the likely scope of work, programme, and costs, and help you navigate Edinburgh’s flood risk requirements from the earliest stages of your project.