Introduction

9.2.1Flooding is a natural process that cannot be entirely prevented. There are four main sources of flooding. Flooding from rivers (or fluvial flooding) occurs when the channel capacity is exceeded and flood waters overtop the river banks. Coastal flooding occurs when inundation of land takes place due to a combination of high tides, wave action and storm surge. Surface water (or pluvial flooding) occurs as a result of high intensity rainfall which can overwhelm drainage systems or cause water to collect in low lying areas. Finally, flooding from impounded water bodies such as reservoirs and dams can arise as a result of overtopping or failure of the impounding structure which in turn may result in a sudden uncontrolled release of flood water into downstream areas. In addition, climate change is generally expected to increase flood risk, albeit that there remains much uncertainty as to the degree of climate change that will occur and the implications for particular areas of Northern Ireland.

9.2.2The effects of flooding on human activity are wide ranging. Floods have the potential to cause fatalities and injury, displacement of people, pollution and health risk, damage to buildings, adverse environmental impacts and to severely compromise economic and social activities.

9.2.3Within Mid and East Antrim, both Ballymena and Carrickfergus include areas considered to be at significant risk of flooding. Numerous other settlements have varying degrees of fluvial and pluvial flooding. Ballymena, Galgorm, Cullybackey, Glarryford and Kells and Connor have all been the recipients of flood defence schemes.

9.2.4The aim of the LDP in relation to flood risk is to prevent inappropriate new development in areas known to be at risk from flooding, or that may increase flood risk elsewhere. Whilst the onus rests with the applicant to identify and consider the potential flood risk to any proposed development by making use of the Flood Maps NI, the LDP is a key tool in the prevention or avoidance of flood risk. Through the LDPs influence on the form of new development, it can assist in the protection of people and property against the impact and incidence of flooding.

9.2.5The SPPS outlines nine regional strategic objectives (paragraph 6.104) for the management of flood risk. The SPPS then sets out strategic policies which must be taken into account in the preparation of LDPs and in the determination of planning applications.

Policy Aims

9.2.6The LDP strategic approach to flood risk is set out in our policy aims below. These policy aims fully embrace the above-mentioned regional strategic objectives and guidelines for LDPs set out in the SPPS. Our operational policies for flood risk are a vital element of a joined up approach involving a number of organisations that together seek to effectively manage flood risk in Mid and East Antrim.

  • To manage development that may be at risk from flooding or that may increase the risk of flooding elsewhere;
  • To protect flood defence and drainage infrastructure; and
  • To promote sustainable drainage solutions to improve water quality.

Implementation

9.2.7The policy aims will be delivered primarily through the strategic policies set out in the remainder of this section.

Policy FRD1 Development within Floodplains

A proposal for development within a floodplain of a river or the sea will not be permitted unless the applicant can demonstrate that the proposal constitutes an exception to the policy.

Where the principle of development is accepted by the Council through being an exception to policy (as set out below), applicants are required to submit a Flood Risk Assessment (FRA) which demonstrates that:

  1. all sources of flood risk to and from the proposed development have been identified; and
  2. there are adequate measures to manage and mitigate any increase in flood risk arising from the development throughout its operational life.

Exceptions

Defended Areas:
  1. A proposal on previously developed land protected by flood defences (confirmed by DfI Rivers as being structurally adequate), provided it does not fall into any of the following categories:
    1. essential infrastructure, such as power supply and emergency services;
    2. development for the storage of hazardous substances;
    3. bespoke accommodation for vulnerable groups, such as schools, residential/nursing homes, sheltered housing; or
    4. any development located close to flood defences.

A proposal involving significant intensification of use will be considered on its individual merits and will be informed by the FRA.

Undefended Areas:
  1. New development within settlements in the coastal floodplain where the land is raised (through infilling), to an acceptable level above the floodplain and subject to meeting all of the following criteria:
    1. the proposal is not dependent on the provision of new coastal flood defences or likely to require such protection as a result of anticipated climate change;
    2. the site is not in an area likely to be at risk from coastal erosion or land instability and the proposed development will not significantly increase such risks in the locality; and
    3. the elevation of development above the floodplain will not unduly disrupt the provision and ongoing delivery of essential services, including access, power, water and wastewater.
  2. Replacement of an existing building, provided it does not include essential infrastructure or bespoke accommodation for vulnerable groups, or involves significant intensification of use.
  3. Development for agricultural use, transport and utilities infrastructure, which for operational reasons has to be located within the floodplain.
  4. Water compatible development such as for boating purposes mooring, navigation and water based recreational use, which for operational reasons has to be located within the floodplain.
  5. The use of land for sport and outdoor recreation, amenity open space or for nature conservation purposes, including ancillary buildings. This exception does not include playgrounds for children.
  6. The extraction of mineral deposits and necessary ancillary development.
Development Proposals of Overriding Regional or Sub-Regional Economic Importance

A proposal within the floodplain that does not constitute an exception to the policy may be permitted where it is deemed to be of overriding regional or sub regional economic importance and meets both of the following criteria:

  1. demonstration of exceptional benefit to the regional or sub-regional economy;
  2. demonstration that the proposal requires a location within the floodplain and justification of why possible alternative sites outside the floodplain are unsuitable.

The applicant is required to submit a FRA for all proposals. Where the principle of development is established through meeting the above criteria, the Council will steer the development to those sites at lowest flood risk.

Minor Development39

Minor development will be acceptable within defended and undefended floodplains subject to a satisfactory FRA.

Flood Protection / Management Measures

The following flood protection and management measures proposed as part of the planning application, in order to facilitate development within floodplains, will not be acceptable:

  1. new hard engineered or earthen bank flood defences;
  2. flood compensation storage works;
  3. land raising (infilling) to elevate a site above the flood level within the undefended fluvial floodplain, where displacement of flood water would be likely to cause flooding elsewhere.

Justification and Amplification

9.2.8As floodplains40 store and convey water during periods of flood, they are of vital importance in the wider flood management system. Any built development will cause piecemeal reduction of the floodplain and potentially remove valuable flood storage area, which may cause or exacerbate flooding elsewhere. Development also has the potential to impair the conveyance function of the floodplain and its ecological integrity. For these reasons, and also the need to limit exposure of people and property to flood risk, built development and infrastructure works, particularly on green field sites, will normally not be permitted.

9.2.9This policy seeks to ensure that development within the floodplains of rivers or the sea is permitted only in exceptional circumstances. The Council will adopt a precautionary approach in assessing proposals in areas that may be subject to flood risk presently or in the future as a result of climate change predictions.

9.2.10DfI Rivers advise Council on the extent of river and coastal floodplains in Mid and East Antrim. Current information on flooded areas, including the spatial definition of present day river and coastal floodplains and those which take account of future climate change predictions, is available on the Strategic Flood Maps NI website at https://www.infrastructure-ni.gov.uk/topics/rivers-and-flooding/flood-maps-ni. These maps are regularly updated as more detailed information becomes available, so the extent of floodplains will therefore change over time.

9.2.11The policy for development in floodplains distinguishes between defended areas and undefended areas.

Defended Areas

9.2.12A ‘Defended Area’ is that part of the floodplain where flooding would normally occur except for the presence of flood defences. Previously developed land protected by existing flood defences, confirmed by DfI Rivers, as being structurally adequate and providing a minimum standard of 1 in 100 year Fluvial, or 1 in 200 year Coastal flood protection, will generally be considered acceptable for development.

9.2.13The flood risk within a defended area cannot be entirely eliminated as the possibility of a flood event exceeding the design limit of the defence and overtopping them (the residual flood risk) will always remain. Another risk arises through the potential for structural collapse and breeching of the defences which could result in sudden and rapid inundation of flood water. Because of these flood risks the policy places restrictions on the location and type of development permissible in defended areas.

9.2.14Development close to flood defences will be resisted as such land will often be low lying and therefore the most susceptible to flooding. Also, it may need to be available for temporary flood storage in a flood event. Before progressing proposals in proximity to flood defences, developers are advised to seek guidance from DfI Rivers on acceptable separation distances.

9.2.15Due to the residual flood risk, the policy operates a presumption against permission being granted for development associated with vulnerable groups. This includes facilities such as children’s nurseries, schools, residential care/nursing homes, sheltered housing and hospitals. This list is not exhaustive.

9.2.16Development proposals for essential infrastructure, such as for emergency services/emergency depots, power supply and telecommunications will be resisted because access and uninterrupted operation cannot be guaranteed in locations where there is a residual flood risk.

9.2.17Development likely to give rise to significant levels of environmental pollution in the event of damage caused by flooding will also be resisted. Therefore proposals for development associated with the storage of hazardous substances, fuel storage depots, sewage treatment works or other development likely to give rise to environmental pollution in the event of flooding will only be granted planning permission where it is demonstrated that an alternative lower risk location is not available and that adequate provision is made for pollution containment so as to prevent a pollution incident in the event of flooding.

9.2.18Development involving a significant intensification of use, such as the conversion of a single dwelling unit to a number of apartments, would be liable to expose more people to the residual flood risk in defended areas. However, this risk must be balanced against other material considerations, for example relating to existing density in the locality or that considered appropriate from a broader planning perspective. Accordingly, Council will determine each application on its individual merits taking account of the scope for mitigation of the residual flood risk.

9.2.19There will be a presumption against development of green field sites in defended areas. As well as exposing more people and property to the residual flood risk, this form of development could remove valuable flood storage should the defences overtop or breach.

Undefended Areas

9.2.20An ‘Undefended Area’ is an area within the floodplain that is not protected by flood defences. This applies to the vast majority of fluvial and coastal floodplains. Undefended areas are at much higher flood risk than defended areas, although the flooded areas are usually more predictable and flood water usually recedes more quickly. There is also the added potential impact of coastal flooding on coastal change.

9.2.21Whilst there is a general presumption against development, it is recognised that in certain cases, particular development or infrastructure has to be in such locations, as alternative lower flood risk sites may be neither feasible nor available. Exceptions to the policy are therefore set out for a range of development types, including for example, agricultural development, minerals development and transport or utilities infrastructure. In regard to agricultural and minerals development, this exception will only apply where the existing unit is located wholly in the floodplain or where the use of other land outside the floodplain would not be feasible and available.

9.2.22The policy provides opportunity for new development in the undefended coastal floodplain on the basis that infilling and land raising to an appropriate level above the floodplain will have a negligible effect on its extent and therefore will not result in additional flood risk elsewhere in the coastal floodplain. Importantly, such development should not generate a present or future need for flood defences nor should it cause or escalate coastal erosion in susceptible areas. As part of the precautionary approach, this exception will be restricted to settlements.

9.2.23Replacement of an existing building may be considered on the basis that this should not normally result in any material increase in the flood risk to the development or elsewhere. The adoption of suitable flood proofing measures through resistance and resilience construction will normally be expected. However the replacement of a building to provide bespoke accommodation allowing for the introduction of vulnerable groups to the flood risk area is unacceptable. Similarly, replacement of a building to accommodate essential infrastructure will be unacceptable as continual access and egress for operational activities will no longer be possible when the area has been cut off during a flood event. Finally, a replacement proposal which involves significant intensification of use, for example through increasing the existing footprint or change of use, will be resisted if this would have the effect of introducing more people to a high flood risk area.

9.2.24The policy allows for the provision of areas for amenity open space, sports, outdoor recreation and nature conservation purposes on the basis that such areas are not generally occupied and are unlikely to incur major damage as a result of flood inundation. Children’s playgrounds are not included in this exception to the policy as such proposals would have the effect of exposing a vulnerable group to flood risk. Ancillary development such as changing facilities, clubhouses, social facilities, 3-G pitches, as well as job-related accommodation for caretakers and staff may be acceptable where justified by the flood risk assessment. Even though these areas are intermittently occupied, proposals will be required to demonstrate mitigation in regard to minimising flood impacts as well as providing for adequate flood warning procedures and safe means of evacuation from the site.

Development Proposals of Overriding Regional or Sub-Regional Economic Importance

9.2.25While most economic development is best located outside of floodplains, it is accepted that certain projects because of their nature, size or site specific requirements, may require a site that happens to fall within a floodplain. In such circumstances the policy allows for development that is demonstrated to be of significant regional or sub-regional economic importance. Normally, such a proposal will be expected to demonstrate its particular contribution to the regional economy. However, a proposal may also be considered acceptable if it provides employment for a substantial number of people living in Mid and East Antrim and potentially adjoining council areas.

9.2.26In regard to such proposals, the applicant must justify the need for a location within the floodplain and also demonstrate why other potential sites outside of the floodplain are not suitable. Subject to the principle of development in the floodplain being accepted by the Council, the applicant will be expected to identify a suitable site in the least vulnerable parts of the floodplain in consultation with DfI Rivers and other statutory consultees as required. The development of greenfield sites in the undefended fluvial floodplain will rarely be acceptable as these areas pose the greatest flood risk.

Flood Management and Mitigation Measures

9.2.27Where Council determines that development is acceptable in principle in the floodplain, then the onus is on the applicant to submit a Flood Risk Assessment (FRA). This must demonstrate measures to be taken to manage and mitigate the identified risks to the proposed development and elsewhere as a result of the development. These measures will be proportionate to the flood risk and generally will be more rigorous in undefended areas than in defended areas where the flood risk (residual) is lesser. Technical details and methodology relating to flood risk assessments and drainage assessments can be found in Appendix I.

Policy FRD2 Protection of Flood Defence and Drainage Infrastructure

A development proposal that would impede the operational effectiveness of flood defence and drainage infrastructure, or hinder access for maintenance or emergency purposes, will not be permitted. This includes the erection of buildings or other structures over the line of a culverted watercourse.

Justification and Amplification

9.2.28Flood defence and drainage infrastructure is critical in providing a level of flood protection to people and property and adequate land drainage.

9.2.29This policy seeks to ensure that such infrastructure is protected from development that would impact on its operational integrity. This includes a presumption against the erection of buildings or other structures over the line of a culverted watercourse in order to avoid damage and facilitate replacement, maintenance or other necessary operations.

9.2.30This policy also seeks to ensure unobstructed access to infrastructure and watercourses for improvement or maintenance purposes. Where a new development proposal is located close to a flood defence, control structure or watercourse, it is essential that an adjacent working strip is retained and protected to facilitate future maintenance by DfI Rivers, other statutory undertaker or the riparian landowners. Normally the working strip should have a minimum width of five metres, but up to 10 metres may be necessary to allow for sufficient access and egress for plant and machinery, and for emergency access. The extent of the reserve will be determined on a case by case basis by the Council, in consultation with DfI Rivers.

Policy FRD3 Management of Development in regard to Surface Water Flood Risk

A proposal for development (except minor development) outside of floodplains will be permitted where the applicant has demonstrated that the risk of surface water flooding (pluvial) to the development, or elsewhere as a result of the proposed development, can be effectively managed through adequate drainage arrangements.

In order to demonstrate this, a Drainage Assessment (DA) will be required for any of the following types of development:

  • A residential development comprising of 10 or more dwelling units.
  • A development site in excess of one hectare.
  • A change of use involving new buildings and/or hardsurfacing exceeding 1000 square metres in area.
  • Where a proposed development is located in an area where there is evidence of a history of surface water flooding.
  • Where surface water run-off from the development may adversely impact upon other development or features of importance to nature conservation or the historic environment.

Justification and Amplification

9.2.31Surface water or pluvial flooding occurs as a result of high intensity rainfall which overwhelms natural or man-made drainage systems resulting in water flowing overland and ponding in depressions in the ground. It has increased steadily with the expansion of urban areas dominated by non-permeable surfaces, the infilling of green spaces and the cumulative effects of minor development such as house extensions and the paving of gardens to provide for patios and car parking. All of these factors have combined to intensify surface water runoff and place additional pressures on the drainage network, particularly during prolonged periods of high intensity rainfall. It is not uncommon for drainage systems to be overwhelmed during such rainfall events, particularly where blockages occur.

9.2.32This policy seeks to ensure that development proposals likely to be at risk from surface water flooding or to exacerbate the risk elsewhere, are only permitted subject to a satisfactory drainage assessment. This must demonstrate that the flood risk can be effectively controlled and mitigated and that the development will not create greater potential for surface water flooding elsewhere. In addition, applicants must use sustainable drainage systems (SuDS) as the preferred drainage solution where appropriate/feasible (see Policy FRD4 Sustainable Drainage).

9.2.33Technical details and methodology relating to drainage assessments can be found in Appendix I Part A.

9.2.34To assist applicants, areas where surface water flooding could be a potential problem are identified on the Strategic Flood Maps NI website at: https://www.infrastructure-ni.gov.uk/topics/rivers-and-flooding/flood-maps-ni or alternatively by contacting DfI Rivers.

Policy FRD4 Sustainable Drainage (SuDS)

A sustainable drainage solution (hard or soft SuDS) for the management of surface water run-off will be required for any development proposal that triggers the requirement for a Drainage Assessment (DA) under Policy FRD3 Management of Development in regard to Surface Water Flood Risk. An exception will be applied where it is clearly demonstrated through the DA that the site is fundamentally unsuitable for a SuDS solution.

A ‘soft SuDS’ solution may also be required for particular zonings for housing and economic development to be identified through the LDP Local Policies Plan.

Management and Maintenance

Planning permission will not be granted until the applicant has satisfied the Council that suitable arrangements will be put in place for the future management and maintenance, in perpetuity, of SuDS required under this policy. A Section 76 planning agreement may also be sought.

Justification and Amplification

9.2.35This policy seeks to further the Executive’s long term goal of delivering a sustainable water sector in Northern Ireland. The RDS, ‘A Long-Term Water Strategy for Northern Ireland (2015-2040)’, and the SPPS all promote SuDS as an important part of the delivery mechanism in contributing to attaining this goal.

9.2.36Council will not only promote SuDS through this policy, but also through key site requirements on specific zonings at Local Policies Plan stage where appropriate. In this way, the LDP will influence developers to use SuDS as the preferred drainage solution, particularly in areas susceptible to surface water flooding and also for relatively large developments where the benefits are likely to be greater and SuDS easier to facilitate. Lands susceptible to surface water flooding are identified on the Strategic Flood Maps NI website at https://www.infrastructure-ni.gov.uk/topics/rivers-and-flooding/flood-maps-ni.

9.2.37SuDS are defined as management practices and control systems designed to drain surface water in a more sustainable way than conventional piped systems. Reducing the amount of surface water run-off to watercourses, or slowing down the rate of discharge, helps to reduce flood risk. There can also be significant amenity benefits for local communities when SuDS schemes are integrated into the wider green/blue infrastructure network.

9.2.38SuDS can vary in size and composition. The appropriateness of a SuDS solution will be determined by the local characteristics of each site including its size, topography, geology, hydrogeology, flood risk and the available discharge points (rivers, drains or sewers). They can vary in size and composition and are often classified as ‘hard’ or ‘soft’ SuDS.

9.2.39The integration of a variety of different techniques usually provides the best solution, however it is acknowledged that in most cases ‘hard SuDS’ will be the preferred drainage solution for developers as these are currently adopted by NI Water. Examples of ‘hard’ SuDS are solutions such as attenuation tanks, permeable paving, and oversized pipes for storm water that are separated from the wastewater system.

9.2.40‘Soft’ SuDS are usually in the form of swales, ponds, wetlands and infiltration beds carved into the landscape to collect water and let it soak naturally down into the ground where it replenishes the water table. These types of SuDS have a role in improving the quality of the run-off from a development and in enhancing nature conservation and biodiversity. Other SuDS include rainwater harvesting and green roofs (see Appendix I Part B for more detail on SuDS).

9.2.41SuDS measures to reduce surface water runoff alone may not be enough – stormwater separation also needs to take place so that rainwater is prevented from entering combined sewers. Applicants should therefore include drainage systems to reduce the amount of rainwater in the combined wastewater system by providing separate drains and by reducing sewer infiltration which will also help improve water quality. New storm connections to the combined sewer system should be avoided as NI Water will not permit a new combined sewer to enter its system without the inclusion of a SuDS system.

9.2.42An appropriate maintenance and management plan for SuDS will be required to be submitted with the planning application to ensure continuity in the future operation of SuDS by, for example, a property management company or for adoption by Council or another public authority. This plan will be required to be agreed with the Council and may involve a S76 planning agreement where necessary to ensure effective ongoing maintenance.

9.2.43Where an applicant considers a site to be fundamentally unsuitable for SuDS, the reasons for this must be set out in the Drainage Assessment and supported by a suitable qualified engineer.

9.2.44The Water and Sewerage Services Act (Northern Ireland) 2016 includes proposals to ensure that SuDS systems are constructed to the appropriate standard. NI Water also now have the power to refuse a surface water connection on the grounds that suitable alternatives to connection to the public sewer exist, or could reasonably be provided (this includes SuDS). The range of SuDS solutions currently considered for adoption by NI Water are identified in Article 161 guidance on the NI Water website https://www.niwater.com/sewers/.

Policy FRD5 Artificial Modification of Watercourses

A proposal for the artificial modification of a watercourse, including culverting or canalisation operations, will only be permitted in either of the following exceptional circumstances:

  • Where the culverting of short length of a watercourse (usually less than 10m) is necessary to provide access to a development site (or part thereof).
  • Where the applicant can demonstrate to the satisfaction of the Council that a specific length of watercourse needs to be culverted for engineering reasons and that there are no reasonable or practicable alternative courses of action.

Applicants are also required to demonstrate that sustainable drainage systems (SuDS) have been considered as an alternative to culverting or canalisation (see Policy FRD4 Sustainable Drainage).

Justification and Amplification

9.2.45The SPPS recognises the artificial modification of a watercourse, including culverting or canalisation of watercourses, as environmentally unsustainable, with potential to increase flood risk. Such operations can adversely impact upon visual amenity and can damage or impair the landscape quality, ecological integrity and biodiversity of watercourses. Some watercourses can themselves be heritage assets as they may have been utilised, diverted and reshaped in the past to become mill races.Culverting creates barriers to the passage of fish, while the higher flow velocities generated cause the unnatural movement of sediment, increased erosion downstream and hinder the future recovery of the watercourse. Whilst culverting may in some instances alleviate local flood risk, it can increase flood risk downstream by the accumulation of higher flows.

9.2.46Applicants will have to demonstrate to the satisfaction of Council, through consultation with DfI Rivers, that there are no reasonable or practicable alternative courses of action. The policy, however, acknowledges that in exceptional circumstances, culverting of a section of a watercourse may be unavoidable. When culverting a short length of a watercourse for access reasons, the length and number of culverts should be kept to a minimum. If part of a watercourse is already culverted prior to the commencement of any development, this does not necessarily mean that it can automatically be lengthened or upgraded to meet the site discharge requirements.

9.2.47Good layout and design should promote the retention of open watercourses as a central amenity feature, although re-alignment or diversion to enhance the quality of the site layout will normally be acceptable where there are no overriding environmental concerns. Incorporating watercourses into the open space requirements for new residential development will be preferred to locating them to the rear of properties where they are difficult to maintain or can become dumping grounds contributing to flood risk. Where possible the removal of culverts and the re-introduction of the natural watercourse should be encouraged.

9.2.48The adoption of sustainable drainage solutions for the disposal of stormwater is a much more sustainable alternative than culverting or other options involving the artificial modification of watercourses. The use of SuDS source control solutions, particularly ‘soft SuDS’ elements such as ponds and swales and their integration into new development schemes as amenity features will therefore be promoted. Such solutions, by negating increased site discharges will reduce the need for flood alleviation/culverting works downstream and any associated maintenance. Applicants are therefore required to demonstrate that SuDS have been considered rather than culverting or canalisation of watercourses, where feasible/appropriate (see Policy FRD4 Sustainable Drainage).

Policy FRD6 Development in Proximity to Controlled Reservoirs

A proposal for new development (other than minor development) within the potential flood inundation area of a controlled reservoir41, as shown on the Strategic Flood Maps, will only be permitted where:

  1. The applicant can demonstrate the condition, management and maintenance regime of the controlled reservoir is appropriate to provide assurance regarding reservoir safety, so as to enable the development to proceed; or
  2. Where assurance on the condition, management and maintenance regime of the relevant reservoir/s is not demonstrated, the application is accompanied by a Flood Risk Assessment, or other analysis, which assesses the downstream flood risk in the event of an uncontrolled release of water due to reservoir failure as being acceptable to enable the development to proceed.

Where the proposal is for the replacement of an existing building and the assurance on the condition, management and maintenance regime of the relevant reservoir/s is not demonstrated, permission will only be granted where the applicant has demonstrated that there is no material increase in the flood risk to the development or elsewhere.

There will be a presumption against development within the potential flood inundation area of a controlled reservoir for proposals that include either:

  1. essential infrastructure (such as emergency services, transport or utilities);
  2. storage of hazardous substances;
  3. bespoke accommodation for vulnerable groups.

Justification and Amplification

9.2.49There are currently 22 confirmed controlled reservoirs in the Mid and East Antrim Council area (see Appendix I Part C for list).

9.2.50Water impounding structures such as reservoirs or dams are a recognised source of flood risk because of the potential for downstream flooding which may ensure if the structure fails, is overtopped, or in the event of a controlled release of water from the reservoir. The potential for rapid inundation associated with such events is likely to have serious consequences for people and property in proximity, particularly for vulnerable groups.

9.2.51New development within the flood inundation area of a controlled reservoir can only be justified where the condition, management and maintenance regime of the reservoir are appropriate to provide assurance regarding reservoir safety. Such assurance must be provided by a ‘suitably qualified engineer’ and supported by DfI Rivers. A ‘suitably qualified engineer’ is a Civil Engineer who at the time of the inspection of the reservoir was a member of a Panel constituted under the Reservoirs Act 1975.

9.2.52The replacement of a building within a flood inundation area will generally be acceptable as in most cases this ought not to increase the likelihood or the impact of flooding to the building or elsewhere as a result of its replacement.

  • 39 - Non-residential extensions with a footprint less than 150 sq. metres. Alterations - development that does not increase the size of buildings, e.g. alterations to external finishes. Householder development - e.g. sheds, garages, games rooms etc. within the curtilage of the existing dwelling in addition to extensions to the existing dwelling. This excludes any proposed development that would create a separate dwelling within the curtilage of the existing dwelling e.g. subdivision of a dwelling house into flats.
  • 40 - The generally flat areas adjacent to a watercourse or the sea where water flows in a flood, or would flow, but for the presence of flood defences. The limits of the floodplain are defined by the peak water level of an appropriate return period event (currently defined as 1 in 100 year or AEP (Annual Exceedance Probability) of 1%for the river or fluvial floodplain and 1in 200 year or AEP 0f 0.5% for the coastal floodplain, incorporating climate change prediction). Floodplains as so defined aredepicted on the Strategic Flood map on the DfI Rivers website.
  • 41 - A Controlled Reservoir is defined by section 1 and 2 of the Reservoirs (Northern Ireland) Act 2015. Generally it is a structure or area that is capable of holding 10,000 cubic metres or more of water above the natural level of any part of the surrounding land.

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