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FAQs

FAQs


General

What should I do if I don’t know what I need?

You can contact GeoSmart by telephone, email, or via one of our online forms to ask a question about a report or specific concern you may have. Our consultants will direct you to the most relevant report and answer your questions.

What should I do if I can’t find the right contaminated land, flood risk or SuDS report?

If you can’t find the right contaminated land, flood risk or SuDS report to suit your needs, do get in touch with a member of our dedicated team to learn more about other products and services that may suit you.

What should I do if my site does not match the ‘assumptions’ of a report?

If your site does not match the assumptions stated for a report, please contact the GeoSmart team to learn more about other products and services we can recommend.

What does “Fixed Price” mean?

GeoSmart’s pricing structure is clear and easy to understand – you pay what you are quoted and no more! Our prices are usually quoted excluding VAT and are completely transparent.

How can I place an order?

Placing an order with GeoSmart couldn’t be easier. Simply register your interest in the report(s) of your choice by filling in the details on the “Order now” form. This does not commit you to making any payment at this stage. Once we have received the form, we will get back to you by phone or email to check your details, respond to any queries you may have, confirm the price of the report(s) you are interested in, and to confirm whether you wish to proceed with an order. If you wish to proceed, we can then take payment over the phone and once your payment is processed we can start work on your report straight away.

What is the importance of making an advance payment?

GeoSmart requires an advance payment for all reports (either full or half the amount quoted depending on the product you are buying). You will receive confirmation of payment when it is received by GeoSmart, which signals that we are ready to make a start with your report. When paying half the full amount in advance, the remaining balance is due on completion of the report and will be requested before your report is issued to you.

What payment methods are accepted?

GeoSmart accepts payment by debit and debit cards (excluding American Express), bank transfer and cheque. The fastest way to proceed is to pay by card, but the choice is yours!

How will my report be delivered?

GeoSmart Reports are delivered electronically as .pdf files to your email inbox. Hard copy reports can be made available on request for an additional charge.

Who will my report be delivered to?

Reports will be delivered to the purchaser unless otherwise stated. GeoSmart do not submit reports to Regulators on your behalf.

Which parts of the UK does GeoSmart cover?

All of GeoSmart’s Reports offer a Nationwide service. We have tried to accommodate as much of the UK as possible for our EnviroSmart Reports. However, some parts of Scotland, Devon and Cornwall are excluded. If your site falls within an excluded area we can still assist, but please do get in touch as we will provide a quote specifically for you.

How do I proceed if my report makes a recommendation for further work?

Our reports make clear recommendations based on risks that we have identified. When further work is required we will specify the best course of action for you in our report recommendations

Can GeoSmart help should I need environmental consultancy services?

If more in-depth, more personalised, or more complex assessments are required, GeoSmart’s sister company ESI Consulting has the benefit of being able to access dedicated and specialist consultants that are available around the clock to provide support. You can contact the GeoSmart team to put you in touch with the right people to help or else contact ESI directly through the details on their website.

What is a Phase 1 Contaminated Land Report?

A Phase 1 Contaminated Land Report is a literature-based review designed to give an overview of the risk of land or groundwater contamination to end-users (house occupiers or workers) and the immediate environment.

A Phase 1 Study collates relevant information from a variety of sources relating to the setting of the site and its previous historical uses. The end product is an interpretive report that contains a qualitative risk assessment, including a conceptual site model that describes the potentially significant sources of contamination, receptors and pathways.

The study involves multiple sources of information often including Ordnance Survey maps, geological and groundwater vulnerability maps, aerial photographs, local and national archives, and newspapers and registers held by relevant regulatory agencies. A site walkover (land investigation) may be required to support the collated desk-based information, to provide details of the current condition of the site, and to gather evidence of potential contamination. When a site walkover is requested, Envirep will generally conduct the walkover following the initial desk study to ensure a ‘best value’ approach in meeting regulations and individual report needs.

What does a Phase 1 Report contain?

A Phase 1 Study collates relevant information from a variety of sources relating to the site setting and its previous historical uses. The end product is an interpretive report that describes the likely presence of any contamination within the subsurface, and the potential risks that this may pose to future site users and the immediate environment. A site walkover may be required to support the desk study information and to provide greater certainty in the report findings.

Who are Phase 1 Contaminated Land Reports intended for?

  • Property developers
  • Self-build
  • Property professionals such as architects, planning consultants and land agents
  • Lawyers and solicitors
  • Lenders, banks or mortgage providers
  • Businesses
  • Insurance companies

Why might a Phase 1 Contaminated Land Report be required?

  • Validating planning applications
  • Meeting planning conditions
  • For land and property purchase
  • For the sale or divestment of a site
  • Due diligence
  • Lending, mortgages, pension funds
  • Business risk assessment

Can contaminated land affect the development process?

If land is highlighted by the local planning authority as potentially being contaminated, the authority’s Contaminated Land Officer is likely to impose a planning condition that an assessment must be completed for clarification. Until that assessment has been completed and accepted by the Contaminated Land Officer, the development should not proceed.

Who is responsible or has a duty of care in contaminated land issues?

The original polluter of the land is officially the person or organisation responsible for any liabilities relating to land contamination. As the pollution may have occurred decades earlier, potentially prior to legislation, this person or organisation may never be found and it is therefore the new owner who will be responsible. It is essential that the person responsible for undertaking the property purchase or development, and their legal advisor, understands the degree of risks and potential financial implications.

Each local authority has a general responsibility for identifying and deciding on necessary actions in relation to contaminated land in its area. Land can potentially be sold when contaminated and the responsibility may end up being passed onto the new owner, or indeed a bank or mortgage lender if the new purchaser was to default. In summary, professional advice should always be sought prior to purchase on any previously developed land.

Do I need a Flood Risk Assessment?

A Flood Risk Assessment is required for any planning application where the site of the proposed development is located within Flood Zones 2 or 3 as defined by the Environment Agency. Such sites are considered to be at risk of flooding and the Environment Agency and local planning authorities have the power to challenge planning applications that have not taken into account all of the flood risks involved.

A Flood Risk Assessment is also mandatory for sites of 1 hectare or greater in Flood Zone 1, and for smaller sites in an area within Flood Zone 1 which has critical drainage problems, as notified to the local planning authority by the Environment Agency. For further information on the relationship between Flood Zones and Flood Risk Assessments, see our news item Flood Zones Explained.

A Flood Risk Assessment should demonstrate how a proposed development will manage flood risk from all possible water sources to the site in question. Changes in flood risk to off-site locations as a consequence of development should also be considered with recommendations provided to avoid increasing such risk.

Is my site located in a Flood Zone?

If you live in England, your site will be located in a Flood Zone as defined by the Environment Agency for planning purposes, but many will be located in Flood Zone 1 with a low probability of flooding. To find out what Flood Zone your site is located in, input your postcode into the Environment Agency Flood Map.

Who are Flood Risk Assessments Intended for?

  • House builders and developers
  • Property professionals such as architects, planning consultants and land agents
  • Lawyers and solicitors
  • Lenders, banks or mortgage providers
  • Businesses
  • Private individuals
  • Insurance companies

Why might a Flood Risk Assessment be required?

  • Validating planning applications
  • Meeting planning conditions
  • For land and property purchase
  • For the sale or divestment of a site
  • Due diligence
  • Lending, mortgages, pension funds
  • Business risk assessment

Delivery

A FloodSmart report can be delivered in 5-10 working days. Delivery of reports requiring Environment Agency consultation and data (FloodSmart Plus and FloodSmart Pro) is dependent on the Environment Agency response times to supply data, which can take up to 20 working days. Typically your report will be dispatched ten working days from receipt of the EA data. A premium delivery is available if your report is urgent – do get in touch and let us know. Your report will be sent in electronic format as a .pdf file straight to your inbox, with hard copies available at an additional cost.

Why commission a FloodSmart FRA Report?

Local planning authorities are likely to request a Flood Risk Assessment for any site which is situated on the modelled flood plain, and within the vicinity of a fluvial or tidal watercourse. Flood Risk Assessments are also requested in areas of low fluvial or tidal flood risk if a proposed development is over one hectare in size and/or lies within a critical drainage area.

Which FloodSmart FRA report is best for you?

Different levels of flood risk assessment reports are required for different purposes. We’ve therefore developed a range of products which are suited to meet the various needs of our clients. Visit our FloodSmart homepage for more information info@geosmartinfo.co.uk.

Who are SuDS Reports are intended for?

  • House builders and developers
  • Property professionals such as architects, planning consultants, and land agents
  • Private individuals
  • Businesses
  • Insurance brokers and lenders

Why is a SuDS Report required?

  • Validating planning applications at Pre-Planning Stage
  • Planning Conditions
  • Building and flood mitigation design
  • Due diligence
  • Code for Sustainable Homes
  • SuDS approval boards (SABs)
  • Lending, mortgages, and pension funds

How do I know what level of SuDS Report I need?

For initial screening at the conceptual design stage a SuDSmart or SuDSmart Plus Report typically supports developers and regulators with infiltration drainage advice. This is the preferred method for managing surface water without increasing flood risk downstream. When infiltration drainage cannot be undertaken at a site due to the underlying ground conditions, other more conventional drainage systems are introduced in our SuDSmart Pro Report (Note: infiltration drainage techniques are also considered when possible).

What does a SuDSmart Pro Report contain?

SuDSmart Pro Reports analyse the potential run-off from a site so that it can be managed effectively to ensure there is no increase in flood risk on or off the site. Post development run-off rates are assessed for a range of storm events including an allowance for future climate change. A drainage strategy is developed to offset the increase in surface water run-off from the new development using the principles of SuDS and the code for sustainable homes. The hydrological context of the site is assessed, along with any potential issues that may affect the SuDS system. A range of potential options are assessed including discharge to the ground, surface water courses or sewerage. The report provides sizes and flow rates for a range of sustainable drainage options that may be considered.

Will my report satisfy the Local Planning Office or LLFA?

SuDSmart Reports can be used to support a planning application at Pre-Planning Stage, or alternatively address a Planning Condition prior to planning being granted. SuDSmart and SuDSmart Plus Reports provide a cursory look at infiltration SuDS which is the preferred method for managing surface water. Whether infiltration techniques are feasible or not will determine the suitability of other SuDS schemes going forward. The level of detail required depends on the specific requirements of your local authority.

You should note that our most detailed report, SuDSmart Pro provides alternative options and preliminary scheme layouts that should be subject to more detailed review at the master planning stage. In our experience, this level of detail is required for more stringent planning authorities or for more complex sites that warrant more detailed assessment.

How do I know what to do next?

All SuDSmart reports include recommendations for next steps. We will always advise on the most cost effective way to move forward and provide details of how to do this whilst meeting in the needs of the planning department.

What if the Local Authority or LLFA request further information to support my application?

GeoSmart are able to provide access to a range of highly experienced senior consultants and engineers through our sister company ESI Ltd., who can provide a more detailed review of your site specifics and planning requirements. ESI also provide soakaway/infiltration testing services and interpretive data review. Please contact a member of the GeoSmart team to put you in touch with ESI when further detailed assessment is required.

What is GeoSmart’s SuDS Infiltration Map (SD50)?

The GeoSmart SD50 map provides an assessment of the capacity of the ground to receive infiltration depending on the nature, thickness and permeability of the underlying material and the depth to the high groundwater table.

  • Allows preliminary assessment of the site without the need for bespoke SuDS design.
  • Use in conjunction with the SuDSmart report range to identify SuDS infiltration suitability and flow/volume design data.
  • Combination may be sufficient to obtain outline planning.
  • Provides customers with clear site risk profile on drainage cost and land area needed.

To discuss the SD50 SuDS screening map and how it can improve your planning submission for your client, contact us today.

Groundwater Flood Risk Map

What is Groundwater Flooding?

Groundwater flooding occurs when sub-surface water emerges from the ground at the surface or into Made Ground and structures. This may be as a result of persistent rainfall that recharges aquifers until they are full; or may be as a result of high river levels, or tides, driving water through near-surface deposits. Groundwater flooding is characterised by:

  • Water flows to the surface or into basements, services ducts and other subsurface infrastructure rising up through floors or directly from the ground. This may be seen as diffuse seepage from the ground, as emergence of new springs or as an increase in spring flows
  • Flooding may last a long time compared to surface water flooding, from weeks to months. Hence the amount of damage that is caused to property may be substantially higher. Likewise closures of access routes, roads, railways etc. may be prolonged
  • Flooding may occur with a delay following periods of high rainfall rather than immediately during storms
  • Emergent groundwater tends to be clear and relatively clean compared to muddy fluvial flood waters, but potential contamination by sewers and brownfield sites poses additional hazards
  • Groundwater flooding or a shallow water table prevents rainfall infiltration and increases the risk of surface water flooding. This means that many surface floods are actually driven by groundwater conditions. But consideration of surface water in isolation and lack of evidence for groundwater conditions leads to incorrect analysis of overall causes

What are potential impacts of Groundwater Flooding?

Whilst groundwater flooding is generally less hazardous to human health than surface flooding, it is more hazardous to property for a given flood depth, producing 2 to 4 times the damage to building fabric and greater disruption to economic activity due to the longer duration of flood events. Also, the impact may be less about surface water depths or velocities and more about the extended saturation of the shallow subsurface with the following consequences:

  1. Damage to basements and other structures below ground
  2. Damage to infrastructure such as buried services and ducts
  3. Sewer flooding
  4. Water damage to property, cultural heritage, crops or sensitive habitats due to saturated conditions
  5. Leaching of contamination from brownfield sites and other sources of contamination
  6. Slope stability issues
  7. Increased likelihood, intensity and duration of surface water flooding due to saturated ground conditions and failure of infiltration drainage systems
  8. Increased cost of construction projects, which will need to incorporate preventive groundwater control measures to prevent what, would otherwise cause harm

In what situation would I need to consult the Groundwater Flood Risk Map?

Groundwater is one of the sources of flooding that may affect a location with potentially important consequences for properties and infrastructure, therefore a review of the groundwater flood risk for a site is recommended prior to a property transaction or property development. An initial screening review will be sufficient for most areas that are at negligible risk of groundwater flooding. Areas that may be at significant risk of groundwater flooding generally require a more detailed site-specific assessment. The Groundwater Flood Risk Map allows users identify whether groundwater may be a source of flooding at their site. It is available at multiple scales and risk resolutions.

What is the coverage and resolution of the Groundwater Flood Risk Map?

The Groundwater Flood Risk map has full coverage over Great Britain. The map is available at multiple scales and risk resolutions:

GW5: The Groundwater Flood Risk map is available at 5m resolution for Great Britain. It classifies groundwater flood risk in every cell on a 5m grid covering Great Britain into one of 4 risk categories: Negligible, Low, Moderate, and High.

GW200-S: The Groundwater Flood Risk map is available on a 200m grid covering Great Britain as a Screening Map. It classifies groundwater flood risk for each cell on that grid into one of two categories: ‘Potentially At Risk’ and ‘Negligible Risk’, based on the maximum risk occurrence within that cell as represented on the higher resolutions product, GW5.

Who is the groundwater flood risk map intended for?

  • House builders and developers
  • Property professionals such as architects, planning consultants and land agents
  • Lawyers and solicitors
  • Lenders, banks or mortgage providers
  • Businesses
  • Private individuals
  • Insurance companies
  • Local Authorities and regulators

What will the map tell me about my property?

The map can tell you whether groundwater flooding is likely to be a concern at a specific site, and will provide recommendations based on the level of groundwater flood risk modelled for that site. However, it does not provide an alternative to a proper site-specific assessment, and a detailed risk assessment should be used for any site where the impact of groundwater flooding would have significant adverse consequences.

The map classification shows on a national mapping scale the areas within which property may be at risk, but this should not be mistaken to mean that groundwater floods will occur across the whole of the groundwater flood risk zones. Mapping limitations and a number of local factors may reduce groundwater flood risk to land and property even where it lies within mapped groundwater flood risk zones.

What data is the map based on?

The groundwater flood risk model used to produce the map incorporates various national scale datasets including Terrain 50 topographical data produced by the Ordnance Survey, LIDAR Digital Terrain Models produced by the Environment Agency, 1:50,000 scale Geological Maps produced by the British Geological Survey, and Groundwater Level data produced by the British Geological Survey. Bespoke in-house hydrogeological and risk models were used to process this data and produce the Groundwater Flood Risk Map. A national database of recorded groundwater flooding events collated by GeoSmart from various sources is used to calibrate and validate the Groundwater Flood Risk Map.

What do the risk categories mean?

Mapped classes combine our understanding of likelihood, model and data uncertainty and possible severity. Likelihood is ranked according to whether we expect groundwater flooding at a site due to extreme elevated groundwater levels with an annual probability of occurrence greater than 1%, taking into account model and data uncertainty. Severity relates to our expectations of the amount of property damage or other harm that groundwater flooding at that location might cause.

CLASS 4: NEGLIGIBLE RISK: There is a negligible risk of groundwater flooding in this area and any groundwater flooding incidence has an annual probability of occurrence of less than 1%.

Comments: No further investigation of risk is deemed necessary unless proposed site use is unusually sensitive. However, data may be lacking in some areas, so assessment as ‘negligible risk’ on the basis of the map does not rule out local flooding due to features not currently represented in the national datasets used to generate this version of the map.

CLASS 3: LOW RISK: There is a low risk of groundwater flooding in this area with an annual probability of occurrence of 1% or greater.

Comments: There will be a remote possibility that incidence of groundwater flooding could lead to damage to property or harm to other sensitive receptors at, or near, this location. For sensitive land uses further consideration of site topography, drainage, and historical information on flooding in the local area should be undertaken by a suitably qualified professional. Should there be any flooding it is likely to be limited to seepages and waterlogged ground, damage to basements and subsurface infrastructure, and should pose no significant risk to life. Surface water flooding, however, may be exacerbated when groundwater levels are high.

CLASS 2: MODERATE: There is a moderate risk of groundwater flooding in this area with an annual probability of occurrence of 1% or greater.

Comments: There will be a significant possibility that incidence of groundwater flooding could lead to damage to property or harm to other sensitive receptors at, or near, this location. Where flooding occurs it is likely to be in the form of shallow pools or streams. There may be basement flooding, but road or rail closures should not be needed and flooding should pose no significant risk to life. Surface water flooding and failure of drainage systems may be exacerbated when groundwater levels are high. Further consideration of the local level of risk and mitigation, by a suitably qualified professional, is recommended.

CLASS 1: HIGH: There is a high risk of groundwater flooding in this area with an annual probability of occurrence of 1% or greater.

Comments: It is likely that incidence of groundwater flooding will occur, with an annual probability of 1% or greater, which could lead to damage to property or harm to other sensitive receptors at, or near, this location. Flooding may result in damage to property, road or rail closures and, in exceptional cases, may pose a risk to life. Surface water flooding and failure of drainage systems will be exacerbated when groundwater levels are high. Further consideration of the local level of risk and mitigation, by a suitably qualified professional, is recommended.

What if my property is shown to be at risk of groundwater flooding?

This does not mean that the property will flood. The GeoSmart Groundwater Flood Risk Map is a national scale product that highlights areas where there is sufficient evidence to suggest that flooding could occur.

However, there are a number of reasons why the national map may be indicating risk where there is no actual risk at a local scale (mapping limitations), and also a number of local factors that may protect land and property even where it lies within confirmed flood risk zones (property protection factors).

Mapping Limitations

Some of the main reasons why the map may be indicating risk in areas where flooding may not actually occur:

  1. The groundwater levels are produced from national scale mapping and models, which may not be representative at a local scale. The sparsity of reliable records of groundwater levels is an important limitation on national scale groundwater mapping and modelling.
  2. In some areas, only a coarse resolution DTM (50m) was available for use in the groundwater flood risk model, which can lead to poor resolution of shallow slopes, and the elevation of a site above an adjacent valley can be under-represented.
  3. Other constituent data-sets, including the geology datasets, are national-scale maps and may not represent local features accurately.
  4. Engineered works are not taken into account in the model. Similarly, artificial drainage works or groundwater pumping or control systems that would limit water table rise to the surface are not accounted for

Property Protection Factors

Some of the main reasons why property within areas at risk of flooding may avoid being flooded:

  1. National groundwater flooding models do not take into account the magnitude of flows emerging from the ground. Therefore while groundwater heads might be indicative of groundwater emergence, the actual amount of flow might not be sufficient to cause flooding at that location (although the accumulated flows downstream might be).
  2. Change in elevation locally may cause groundwater emergence to be localised away from the property, keeping the water table below hazardous levels at the property.
  3. Even if emergent groundwater was at a rate sufficient to cause local flooding, the nature of the urban man-made subsurface tends to drain water away before it reaches the surface. Sewers, granular fill around utilities and road sub-grade are all highly permeable formations that would be able to drain quite high groundwater flows away. This tends to move the groundwater flooding problem down the catchment.
  4. Drains on or near the property or other property protection such as break layers or membranes incorporated in the building may act to prevent water reaching locations where impacts would occur.

In summary, it is recommended that a more detailed risk assessment by a suitably qualified specialist should be undertaken for any sites that occur in mapped zones of groundwater flood risk where the impact of groundwater flooding would have significant adverse consequences. Decisions such as whether to proceed with a property transaction should not be made on the basis of the map classification alone. Even in the event that groundwater flood risk is confirmed through site-specific assessment, potential risk mitigation measures can usually be identified which could enable the property transaction or development to proceed.

What is the update cycle?

The map is updated on a 6 month cycle to take advantage of newly released data as soon as it comes out.

How is the map validated?

The map has been through a rigorous internal QA process, and has been reviewed by external experts. At every update cycle, it is reviewed against a national database of groundwater flooding events to verify its validity.

My house flooded recently, but the map says it is at negligible risk of groundwater flooding.

Other sources of flooding should be considered in this case, which are not represented on the Groundwater Flood Risk Map. These include fluvial and tidal flooding, surface water flooding, and flooding produced by springs.

My property is in a fluvial flood plain, but also shows up as being at risk of groundwater flooding. What does this mean?

This suggests an important hydrological connection between the river and the groundwater in this area. Due to the groundwater contribution, flooding in this area may occur more frequently and for longer durations than would be expected from fluvial flooding alone.

What mechanisms of flooding are represented on the map?

The two most pervasive mechanisms of groundwater flooding are represented on the Groundwater Flood Risk Map. These are bedrock flooding and permeable superficial deposits flooding.

Bedrock Flooding: After extreme rainfall, groundwater levels, in places, rise to intercept the ground surface. Rises in groundwater level may also be superimposed upon above average groundwater levels in the aquifer prior to the rainfall. Water tables typically reach the surface first in (dry) river valleys, where the emerging water can drain away. With increasing groundwater levels, the carrying capacity of the drainage channel is exceeded and a surface flood commences. This is also known as ‘clearwater’ flooding because of the relative clarity of groundwater compared to fluvial flood water.

Permeable Superficial Deposits Flooding: Where groundwater in permeable superficial deposits (PSD) is in good hydraulic contact with a river or the coast, flooding can occur during periods of high river stage or tide. This mechanism is particularly exacerbated when the PSD overlie low permeability strata.

If a depression is set back from the river, with a connection via PSD then this might be prone to groundwater flooding even if it is protected from overland fluvial flooding. In conditions of less extreme floods, groundwater flooding often occurs in flood plains due to high in-channel river levels, before the river overtops its bank, or after it has retreated back into its channel. It is therefore often difficult to distinguish from river flooding. Effectively, the subsurface flow path results in more extensive, frequent, and prolonged inundation of flood plains that occur on permeable superficial deposits connected to rivers.

Other mechanisms of groundwater flooding that are not represented on the Groundwater Flood Risk Map are:

  • Groundwater flooding produced by spring flows that exceed normal conditions, and therefore overwhelm their drainage channels.
  • Groundwater flooding as a result of water table rebound. The effect of rising groundwater levels beneath some cities, mineral extraction areas, or around water supply boreholes due to reduced abstraction has not been modelled.

GeoSmart SD50

When should I consult the GeoSmart SuDS Infiltration Suitability Map?

Government policy across the UK is to introduce sustainable drainage systems (SuDS) to control site rainfall run-off via conditions in planning approvals. A range of SuDS options are available, but guidance states that infiltration into the ground, where feasible, is the preferred method for managing surface water run-off on site without increasing flood risk downstream. Regulations on SuDS vary locally, and should be verified with your local planning authority.

The GeoSmart SuDS Infiltration Suitability Map should be consulted as part of the site development and design process or when considering land purchase.

The SuDS map supports the following requirements:

  • Validating planning applications at Pre-Planning Stage
  • Planning Conditions
  • Building and flood mitigation design
  • Due diligence
  • Code for Sustainable Homes
  • SuDS approval boards (SABs)
  • Lending, mortgages, and pension funds

The map provides an initial assessment of the feasibility of infiltration SuDS at a site and recommendations on site investigations to support Infiltration system design, where relevant. It is intended to support property professionals at an early stage in the development planning process in understanding the SuDS options available at a site and the risks and costs associated with them.

What are Sustainable Drainage Systems (SuDS)?

A sustainable drainage system (SuDS) is designed to replicate, as closely as possible, the natural drainage from the Site (before development) to ensure that the flood risk downstream of the Site does not increase as a result of the land being developed. SuDS can also significantly improve the quality of water leaving the Site and can enhance the amenity and biodiversity that a site has to offer.

There are a range of SuDS options available to provide effective surface water management that intercept and store excess run-off. When considering these options the preferred destination of the run off should be assessed using the order of preference outlined in the Building Regulations Part H document (HM Government, 2010) and DEFRA’s Draft National Standards for SuDS (2011):

  1. Discharge to the ground
  2. Discharge to a surface water body
  3. Discharge to a surface water sewer
  4. Discharge to a local highway drain
  5. Discharge to a combined sewer

For general information on SuDS see www.susdrain.org.

Who is the GeoSmart SD50 intended for?

  • House builders and developers
  • Property professionals such as architects, planning consultants and land agents
  • Businesses
  • Private individuals
  • Insurance brokers and lenders
  • Local Authorities and regulators

What is the coverage and resolution of the GeoSmart SD50?

The GeoSmart SuDS Infiltration Suitability Map has full coverage over Great Britain with a resolution of 50m.

What information does the GeoSmart SuDS Infiltration Suitability Map provide?

The GeoSmart SuDS Infiltration Suitability Map map consists of an Infiltration Potential Map which represents three categories, Low, Moderate, High, which indicate the potential for successfully implementing an infiltration system at a given location. The mapped infiltration potential is based on data related to the geology of underlying superficial deposits and bedrock, their permeability, the thickness of the superficial deposits, where they exist, and high groundwater levels.

What do the different categories on the GeoSmart SuDS Infiltration Suitability Map indicate for a site?

  • Low Potential: There is a low potential for infiltration SuDS in parts of the Site. It is likely that the underlying geology at the Site, or in areas of the Site, is relatively impermeable which would limit the effectiveness of a proposed infiltration SuDS scheme
  • Moderate Potential: Infiltration SuDS are potentially suitable subject to further field investigation. One or more of the following three factors may have led to the moderate Potential classification for a given cell: a) the permeability of the receiving formation can vary over a large range, and field investigation is necessary to evaluate whether the infiltration capacity at that location will be sufficient for the successful deployment of an Infiltration SuDS system. b) Superficial Deposits at that location may be thin and a significant difference in permeability is expected between bedrock and Superficial deposits. For these locations, the thickness of superficial deposits needs to be verified and the design of the Infiltration system must take into consideration a potentially significant change in permeability or infiltration capacity over the depth of the system. c) The risk of a shallow winter-time water table and groundwater flooding in cases of extreme elevated groundwater levels is significant. For these locations, the height of the seasonal water table needs to be verified based on field data to ensure that it remains below the base of the Infiltration system. Furthermore, a detailed, site-specific assessment of groundwater flood risk, and the functioning of the soakaway under such conditions is recommended
  • High Potential: Infiltration SuDS are likely to be suitable due to the high permeability of underlying formation. Where infiltration is into permeable superficial deposits overlying potentially impermeable bedrock, the thickness of superficial deposits seems sufficient for standard soakaway design. Groundwater flood risk is low or negligible. Still we would advise field verification of permeability and seasonal water table

Cost and Delivery

For sites less than 1 ha, a close-up of the Infiltration Potential map for the site can be obtained via the SuDSmart Standard, Plus and Pro Reports, along with site analyses and recommendations related to site investigations to inform infiltration system design and additional supporting information. For larger sites, the GeoSmart SuDS Infiltration Suitability Map can be obtained for any area boundary. The map is also available for purchase at county or national scale.

What will the GeoSmart Sustainable Drainage Map tell me about my property?

The map will tell you whether infiltration is likely to be a feasible solution for managing rainfall runoff at your site. Where relevant, it will also provide information that supports the initial conceptual design of an infiltration system and recommendations on field investigations required to support the detailed design of such a system. Whether infiltration techniques are feasible or not will determine the suitability of other SuDS schemes going forward. The map can therefore provide information early on in the property development process related to the range of SuDS options available to a site and expected costs of implementing SuDS at a site.

What data is the GeoSmart Sustainable Drainage Map based on and how are these data used to derive Infiltration Potential?

The GeoSmart SuDS Infiltration Suitability Map incorporate various national scale datasets including 1:50,000 scale Geological Maps produced by the British Geological Survey and Permeability Data and Superficial Deposit Thickness. GeoSmart’s SuDS Infiltration Suitability Map also uses information from GeoSmart’s Groundwater Flood Risk Map, which is based on national scale datasets of topography and groundwater levels, in addition to bespoke in-house hydrogeological and risk models.

What is the update cycle?

The map is updated on a 6-month cycle to take advantage of newly released data as soon as it comes out

How is the map validated?

The map has been through a rigorous internal QA process. At every update cycle, it is reviewed against a national database of site-specific SuDS assessments to verify its validity and identify any required model improvements to be incorporated into the next updated release.

GWFlood FAQs

What timescale are forecasts delivered on?

We update our forecast every working day. This is sufficient when there are no imminent groundwater flooding incidents. If incidents are likely, or are occurring then we increase the service to daily, then twice daily. A weekly synopsis of the outlook for groundwater flooding is prepared by our experienced hydrogeologists in support of the daily forecasts.

How are forecasts delivered?

Forecasts are provided on a regional scale for river catchments and sub-catchments. If you are interested in a particular community, or assets then the forecast can be delivered for each.

We send you:

  1. The probability of groundwater flooding within 15 days.
  2. The most likely timescale (<15 days) until flooding commences.
  3. The quickest feasible timescale in which flooding might commence.

We send the daily forecasts by email, which will include a link to download the forecast as a data file and catchment risk map. We also provide a web mapping interface.

A weekly synopsis report is provided reviewing the outlook and current groundwater situation with accompanying forecast groundwater hydrographs. The potential impact and duration of groundwater flooding events is reviewed as part of the report.

What file types do you use to send the forecasts?

We currently deliver as csv files (one line for each catchment), ESRI shapefiles, and PNG images. In addition the web mapping interface gives a spatial overview of the forecast. Other file types can be delivered on request.

What is the spatial resolution?

Our standard forecast is delivered for 302 river catchments across southern and south east England (soon to be c. 500 catchments from southern England to Yorkshire). But if you have a particular asset, community or location we can provide a specific forecast.

I have one principal asset - can you provide a forecast for that?

Yes – for a small set-up fee in addition to the annual licence we can enter your location into the system and generate a daily forecast for your specific location, community or asset.

Is this a risk map?

A base map is used to highlight the forecast for groundwater flood-prone river valleys. The GeoSmart Groundwater Flood Risk Map can be used in tandem with the forecasts to highlight the particular locations within a catchment that might be at risk.

How does the system work?

The GeoSmart groundwater forecast model combines historic climate and borehole data plus live telemetry feeds and daily updates of the most accurate ensemble weather forecasts. Predicted groundwater levels are used to map risk predictions over a range of time scales for 5, 15, 30 and up to 90 days in advance. As with any weather forecast the uncertainty in the predictions increases with the extent of forward prediction. Results indicate the percentage likelihood that groundwater flooding will occur within the prescribed time period and potential flooding duration.

What are threshold levels?

Threshold levels are set relative to the forecast groundwater elevations to indicate the likely onset of groundwater flooding. Where required additional threshold levels can be set by the client for specific assets or communities.

What subscriptions are available?

You can subscribe to get a forecast for one location, or on a wider regional scale. Contact us for licensing costs.

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