Ministerial guidelines
The Planning System and Flood Risk Management: Guidelines for Planning Authorities
Flood Zones A, B and C, the sequential approach and the Justification Test for development in areas at risk of flooding.
Department of the Environment, Heritage and Local Government and the Office of Public Works · November 2009 · 81 pages
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- 4.13 4.14 4.15 Strategic Flood Risk Assessment The steps in the development plan process and its Strategic Environmental Assessment need to be supported by appropriate analysis of flood risk. Again a staged approach should be adopted, carrying out only such assessment as is needed for the purposes of decision-making. All stages may not be needed to complete a flood risk assessment. This will depend on the level of risk and the potential conflict with proposed development and the scale of mitigation measures being proposed. For the purposes of applying the sequential approach, once a flood risk has been identified it can be avoided, or if following the initial assessment the risks are too significant, again avoidance may be the outcome. These iterations should be captured in the SEA. Where development is planned in flood risk areas, a detailed flood risk assessment may have to be carried out within the SFRA, so that the potential for development of the lands and their environmental impact can be assessed. A Strategic Flood Risk Assessment (SFRA) can therefore encompass all levels of flood risk assessment. These are outlined in chapter 2 and described in more detail in Appendix A. Local authorities will need to undertake an identification exercise, an initial assessment and in some locations across the plan area detailed flood risk assessments. The SFRA is initially based on existing sources of information but it may require the gathering of new information for all or part of the area of the development plan or local area plan through a detailed flood risk assessment. Taking account of the above, a plan at county level, will not normally have to undertake detailed flood risk assessment involving the production of a flood risk map for all watercourses or coastal frontage. In general, this will only be necessary if it is intended to zone land for development or identify the location of future strategic infrastructure within flood risk areas. Where flooding is not a major issue in the location of new development, as will be the case in many county development plans, a less detailed approach will be required than in core urban areas with high development pressures and significant flood risk issues. The SFRA will provide more detailed information on the spatial distribution of flood risk to enable adoption of the sequential approach and to identify where it will be necessary to apply the Justification Test. Each SFRA is designed individually to match the availability of data, scale and nature of the flood risk issues, the type of development planned and any focus on regeneration. Therefore SFRAs for county and city plans will be different, and whilst some of these may well be combined due to the common sources of flooding, county SFRAs will contain some detailed investigation of how the sequential approach should be applied in key towns or to the identification of the location of future strategic infrastructure within flood risk areas. City development plan SFRAs will be more detailed and may tend to focus on how residual flood risks will be managed. For information regarding Strategic Flood Risk Assessment at city and county levels see Fig. 4.1. 4.16 33 Guidelines for Planning Authorities The Planning System and Flood Risk Management
- The SFRA should provide sufficient information to make sound planning decisions, including an identification and assessment of the impacts and mitigation strategies for development options. The SFRA should also be used to ensure that the elected members have the information with regard to the Strategic Environmental Assessment, application of the sequential approach and, if necessary, the Justification Test, in coming to decisions about the draft development plan and all subsequent stages. The structure of the SFRA should reflect the multiple uses that this document has within the planning process and beyond. The key outputs from an SFRA and the key steps in its delivery are outlined in detail in Appendix A, The objectives of an SFRA are summarised below: To provide for an improved understanding of flood risk issues within the development plan and development management process, and to communicate this to a wide range of stakeholders; To produce an assessment of existing flood defence infrastructure and the consequences of failure of that infrastructure and also identification of areas of natural floodplain to be safeguarded; To produce a suitably detailed flood risk assessment, drawing on and extending existing data and information, leading to a suite of flood risk maps that support the application of the sequential approach, in key areas where there may be tension between development pressures and avoidance of flood risk; To inform, where necessary, the application of the Justification Test; To conclude whether measures to deal with flood risks to the area proposed for development can satisfactorily reduce the risks to an acceptable level while not increasing flood risk elsewhere; and To produce guidance on mitigation measures, how surface water should be managed and appropriate criteria to be used in the review of site specific flood risk assessments. In some instances improvements to existing flood defences may be required to manage residual flood risks. Where such flood defence works are considered, the SFRA should include an appraisal of the extent of any works required to provide or raise the flood defence to an appropriate standard. In addition the SFRA should identify local or surface water flooding issues that may influence the zoning of land. 4.17 4.18 :: :: :: :: :: 4.19 :: 34 4
- Fig. 4.1: Strategic Flood Risk Assessments exemplified at county and city scale 35 Guidelines for Planning Authorities The Planning System and Flood Risk Management Undefended flood risk for a 1% flood event (taken from flood Zone map when available or from a modelled assessment). Actual risk for a 1% flood event (defences in place). Residual risk arising from 0.1% flood event overtopping defences. A: B: C: Detail of SFRA carried out for City X: Background Map Source: Map data (c) OpenStreetMap (and) contributors, CC-BY-SA 0.1-0.3 0.3-0.6 0.6-0.9 0.9-1.2 0.1% AEP Max. Depth (m)Very high risk High risk Moderate risk Little risk identified Flood Zone A Legend Regional Flood Risk Appraisal. Spatial identification of flood risk (not to scale): B CA Town Y Town W Town Z City X A county level view of Strategic Flood Risk Assessments undertaken (left) is supported by the following information: Town Y (LAP) Initial Assessment for zoning purposes: Map is based on flood zones constructed from available information. Conclusion: Sufficient available land in lower flood risk zones. All lands in town zoned to AVOID flood risk. City X (development plan) Detailed Assessment: New river model used to graduate flood risk in key regeneration areas. Land zoned for lower vulnerability use, and mitigation strategy developed for mixed use development. Town W (LAP): Initial assessment indicates little development pressure/minor planned development, no further stages in flood risk assessment required. Town Z: Initial assessment shows impacts elsewhere and scale of mitigation measures are significant. Zoning of lands to avoid indicative Flood Zone A and B. :: :: :: ::
- 4.21 4.22 4.23 Strategic Flood Risk Assessment and SEA The SEA process addresses any likely significant effects on the environment and their amelioration, from the implementation of development plans through all stages of the plan-making process. Flood risk identification (Stage 1) to assess whether full flood risk assessment is required, should ideally be carried out in a manner that is integrated with the SEA process rather than constituting an additional and separate process. Any subsequent stages of flood risk assessment should also be carried out in a way that is integrated with the SEA process. Within the process of preparing the draft development plan, the draft SEA environmental report will consider the environmental effects of the draft plan against environmental criteria for the plan area, including mitigation measures and future monitoring of effects. As with SEA, it will be important to knit flood risk assessment into the development plan structure, and provide a coherent and transparent approach as to how it has been considered in making spatial planning decisions. A summary of the likely effects of the plan on the environment, through exposing new development and their occupants to potential flood risks and any adverse impacts as a result, will be addressed in the SEA process and summarised in the environmental report element of the overall development plan. Development plan Justification Test Having prepared a Strategic Flood Risk Assessment and mapped flood zones as part of its development plan review process and any more detailed flood risk assessments as necessary, situations can arise where a planning authority will need to consider the future development of areas at a high or moderate risk of flooding, for uses or development vulnerable to flooding that would generally be inappropriate as set out in Table 3.2. In such cases, the planning authority must be satisfied that it can clearly demonstrate on a solid evidence base that the zoning or designation for development will satisfy the Justification Test outlined in Box 4.1 opposite. 4.20 36 4
- Where, as part of the preparation and adoption or variation and amendment of a development/local area plan1, a planning authority is considering the future development of areas in an urban settlement that are at moderate or high risk of flooding, for uses or development vulnerable to flooding that would generally be inappropriate as set out in Table 3.2, all of the following criteria must be satisfied: The urban settlement is targeted for growth under the National Spatial Strategy, regional planning guidelines, statutory plans as defined above or under the Planning Guidelines or Planning Directives provisions of the Planning and Development Act, 2000, as amended. The zoning or designation of the lands for the particular use or development type is required to achieve the proper planning and sustainable development of the urban settlement and, in particular: Is essential to facilitate regeneration and/or expansion of the centre of the urban settlement2; Comprises significant previously developed and/or under-utilised lands; Is within or adjoining the core3 of an established or designated urban settlement; Will be essential in achieving compact and sustainable urban growth; and There are no suitable alternative lands for the particular use or development type, in areas at lower risk of flooding within or adjoining the core of the urban settlement. A flood risk assessment to an appropriate level of detail has been carried out as part of the Strategic Environmental Assessment as part of the development plan preparation process, which demonstrates that flood risk to the development can be adequately managed and the use or development of the lands will not cause unacceptable adverse impacts elsewhere. N.B. The acceptability or otherwise of levels of any residual risk should be made with consideration for the proposed development and the local context and should be described in the relevant flood risk assessment. Box 4.1: Justification Test for development plans 1 2 3 (i) (ii) (iii) (iv) (v) 1Including Strategic Development Zones and Section 25 Schemes in the area of the Dublin Docklands Development Authority. 2In the case of Gateway planning authorities, where a number of strategic growth centres have been identified within the overall area of the authority, the Justification Test may be applied for vulnerable development within each centre. 3See definition of the core of an urban settlement in Glossary of Terms. 37 Guidelines for Planning Authorities The Planning System and Flood Risk Management
- Other development plan objectives Plans should also be pro-active in addressing flooding by including, for example, general policies to protect, improve or restore floodplains or the coastal margins. Planning authorities should consider whether there are areas where a previous and natural flood risk management function can be restored through appropriate actions, such as managed re-alignment of existing coastal defences or river or wetland restoration projects and the provision of flood storage. As well as restoring the flood risk management function, actions such as those above may provide opportunities to introduce green/open space within congested urban areas, with consequent benefits to amenity and biodiversity as well as helping to reduce the future impact of climate change. Other objectives that planning authorities should consider for inclusion in their development plans are: Preservation of riparian strips alongside river channels free of development and of adequate width to permit access for river maintenance; Development management standards and checklists to provide more detailed assessment frameworks for planning applications where flooding is or may be an issue, including highlighting the need for assessment of types of flooding other than river and coastal flooding and of the impacts of run-off from development; Requirements for development proposals to be accompanied by a detailed explanation of how the Development Management Justification Test has been met, where vulnerable development is being considered in the flood risk zones; Design and development standards that seek to manage the risks to acceptable levels through flood-resistant and flood-resilient construction methods, where avoidance is not possible and requirements such as Sustainable Drainage Systems and other design features (outlined in Appendix B); and The provisions of flood risk management infrastructure such as flood defences including the programme of planned investment by the OPW, a local authority’s own works or the provision by private developers. Actions to be carried out in the plan area relating to flood risk management or infrastructure whether the responsibility of the planning authority or may be required of other parties such as developers, to facilitate development or to protect existing development, including any further studies or plans to be prepared relating to flood risk management. Fig. 4.2 outlines how the key processes of the development plan and SEA and can be aligned with the strategic assessment of flood risk. 4.24 4.25 :: :: :: :: :: 38 4
- 39 Fig. 4.2: Development plan preparation where flood risk is scoped as an issue Guidelines for Planning Authorities The Planning System and Flood Risk Management Development Plan/LAP* SEA Strategic Assessment of Flood Risk *Where an Environmental Report is required Survey & analysis Issues Studies/Issues papers Studies Strategic Flood Risk Assessment Scoping with env. authorities Environmental criteria Strategic effects Flood risk criteria (from SFRA) Assess against Strategic Flood Risk Assessment Refer to detailed assessment using SFRA Account for residual flood risk Flood risk indicators Apply sequential approach Gather baseline info; undertake gap analysis / produce inception report Strategic options Evaluation Preferred options Policies Objectives Supporting information Strategic evaluation Detailed evaluation Mitigation Monitoring etc. Pre-Draft StageDraft Plan
- 4.28 Existing undeveloped, zoned areas at risk of flooding Information about flooding and flood risk is improving and will improve further as a result of national exercises undertaken by OPW and others, and implementation of these Guidelines. Future flood risk assessments required to support the development plan process may highlight existing, undeveloped areas which, on their own merits, were zoned for development in previous development plans but which new information indicates may now, or in the future, be at risk of flooding. In the type of case set out above, planning authorities should reconsider the zoning objective of the current or previous plan for any such lands where flood risk is assessed to be potentially significant and likely to increase in the future. Following this reconsideration, planning authorities may decide to: Remove the existing zoning for all types of development on the basis of the unacceptable high level of flood risk; Reduce the zoned area and change or add zoning categories to reflect the flood risk; and/or Replace the existing zoning with a zoning or a specific objective for less vulnerable uses; Prepare a local area plan informed by a detailed flood risk assessment to address zoning and development issues in more detail and prior to any development; and/or Specify, in exceptional circumstances and where the criteria of the Justification Test have been met, design of structural or non-structural flood risk management measures as prerequisites to development in specific areas, ensuring that flood hazard and risk to other locations will not be increased or, if practicable, will be reduced. Local area plans The preparation of a development plan in accordance with these Guidelines should identify the key flooding issues that need to be addressed at the local area plan (LAP) level. The local area plan is now an important part of the planning process allowing for more detailed and area-based planning. Many LAPs are equivalent in size to smaller development plans. Where flood risk may be an important issue as flagged in the relevant development plan, they must follow the methodology and staged approach including SEA, as outlined above. However, resolving flood risk issues and its impact on deliverability of zoned land should be addressed in the development plan primarily. 4.26 4.27 :: :: :: :: :: 40 4
- 4.29 SEAs are not mandatory for certain LAPs below a certain scale and nonstatutory plans. However, a screening process is required for most LAPs and this should identify any significant flooding issue. Indeed, the SEA process for LAPs is triggered where the plan is likely to have a significant effect on the environment regardless of thresholds. While non-statutory plans and studies have an important role to play in promoting integrated and sustainable development, they are not an appropriate means of strategic area planning where flood risk is a significant issue. The preparation of such plans should be within the context of a statutory development plan or local area plan, which has fully considered flood risk in accordance with these Guidelines and determined the appropriate policies and constraints within which non-statutory plans should be prepared. In other cases, planning authorities should use their discretion in addressing flood risk in a manner more appropriate to small-scale LAPs. 41 Guidelines for Planning Authorities The Planning System and Flood Risk Management Fig. 4.3: Use of flood risk assessment at local / master planning level Predicted Flood Depths (m) for the 1% plus Climate Change AEP Event Development Constraints Plan Low flood hazard Limited mitigation required 0 to 0.50 0.50 to 0.70 0.70 to 0.90 0.90 to 1.10 1.10 to 1.30 1.30 to 1.50 1.50 to 1.70 1.70 to 1.90 Moderate flood hazard Some mitigation required High flood hazard Significant mitigation required Potential evacuation routes
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