1 Background On the 1st October 2019, following a severe flood event in the Village of Laxey, 62 properties experienced flooding. The area most affected was Glen Road where 51 of the 62 flooded properties are located. This report provides details of the proposed weir replacement which reduces the head level of the river. During the October flood, debris built up behind the existing weir structure which, along with other factors, contributed to the overtopping of the highway wall adjacent to Glen Road. This was a result of the elevated upstream levels and collapse of the highway wall immediately upstream of the MER weir, subsequently inundating Glen Road and flooding a lot of the properties on Glen Road. Following the floods of 2019, the superstructure of the weir was removed to prevent future blockages and the Department proposes to remove the sub-structure of the weir this summer which will include re-grading of the Laxey River bed in this area which will include the installation of a rock ramp which will control the river flows and prevent adverse river bank and bed level erosion. These proposed works are the subject to this planning application.
2 Location and Brief Description of Proposed Works The Department of Infrastructure is undertaking a series of flood alleviation works for Laxey River programmed for construction in 2021/22. The works will comprise of 3 elements of a proposed continuous flood wall on the left bank, replacing and reconstructing existing informal flood defences, constructing new walls incorporating flood resistant access arrangements where necessary; improvements to channel conveyance and long term integrity of bank side structures which will include the removal of the remainder of the weir structure and the subsequent re-grading and installation of a rock ramp to control flows and prevent erosion. The above mentioned will be the subject of 4 separate planning applications. The subject matter for this planning application will be the replacement of the MER weir, lower platform and side sluice with a rock ramp weir situated within the river to the north of Victoria Terrace on Glen Road in Laxey. Details and location of the proposed rock ramp are presented in Appendix A.
3 Political Policy The Council of Ministers programme for Government 2016 – 2021 states the strategic objectives of Tynwald over a five year period. On page 11 of the document, one of the policy statements declares that… “We will continue to invest in sea defences and in reducing flooding and coastal erosionrisks for those areas identified as high risk in our national strategy”
The development of this strategy for the Isle of Man, which covers three sources of flooding and coastal erosion, is a pioneering step for the Island and will contribute to the economic, environmental and social resilience of the Isle of Man to current and future climate risks. The report informs the Isle of Man Government’s first strategy, collectively assessing flooding and coastal erosion risks, identifying the locations at most risk and suggesting potential responses to increase the resilience of these locations.
The Strategy Evidence Report was developed by JBA Consulting on behalf of the Department for Environment, Food and Agriculture (DEFA) and a wider Strategy Steering Group including representatives from the Department of Infrastructure (DOI) and Manx Utilities (MUA). The report is intended to comply with and assist in the delivery of key relevant policy, including the Mid-Term Report from the Council of Ministers on the Agenda for Change, 2014; Isle of Man Government Policies on adapting to and mitigating Climatic Change, 2014; Isle of Man Government Policies on adapting to and mitigating Climatic Challenges and Sustainable Development, 2015; The Island Development Plan, 2016; The Isle of Man Biodiversity Strategy, 2015; and the Regional Sewage Treatment Strategy, 2009.
4 Planning and other Policy Framework The weir falls within the scope of The Laxey and Lonan Area Plan (2005). Within the Laxey Map, the Glen Road side of the riverbank is zoned as being an area of ecological interest; with those properties adjacent to the river being zoned as residential. The left side of the watercourse is for the most part zoned as open space.
The weir is situated within the river to the north of 1 Victoria Terrace, Glen Road, Laxey and falls within the Laxey Conservation Area – Map 6 referred to in the Town and Country (Planning Development) Order 1990.
The Isle of Man Strategic Plan 2016 also applies and the key policies which impact upon the proposed development are as follows;
General Policy 2 which states the development should (b) respect the site and surroundings in terms of scale, form and design; (d) does not adversely affect the protected wildlife or locally important habitats on the site or adjacent land, including water courses; and (g) does not affect adversely the amenity of local residents or the character of the locality.
Environmental Policy 10 indicates that where development is proposed in an area where there is potential risk of flooding, the application must include a flood risk assessment and details of flood mitigation measures.
Environment Policy 24 sets out the need for supporting environmental information to be provided.
Environment Policy 35 indicates that within Conservation Areas, the Department will only permit development that would preserve or enhance the character and ensure that the special features contributing to the character and quality are protected against inappropriate development.
5 Proposed Option and Flood Risk Statement
Immediately after the flood levels abated following the severe flood event of October 2019, the Department of Infrastructure swiftly proceeded, with emergency actions, to remove debris material from the river and carry out demolition of failed sections of the Glen Road retaining wall. The failed sections of the wall were then reconstructed in reinforced concrete approximately 300mm higher than the original wall to give additional protection from flooding. For aesthetics the wall was then faced in Manx stone.
There are multiple weir structures in the Laxey River adjacent to Glen Road that are in a poor condition and in need of replacing. The existing weir structure is in a poor condition with a large scour hole at the left toe of the weir. The concrete platform is also in poor condition with steel reinforcement protruding from the platform and again, a large scour hole exists on the left side of the channel. If the existing structures were to fail, it could cause blockages downstream resulting in severe flooding. Included with this Statement of Case is a location plan showing the various structures to be removed as well as the proposed replacement structure; a rock ramp.
The existing weirs reduce the riverbed level from 16.02mAD02 to 13.36mAD02 dramatically reducing the head level of the river whereas the proposed rock ramp aims to reduce the riverbed by the same amount but by utilizing a gradual gradient as advised by flood specialists JBA Consulting which will in turn help to alleviate flooding within Laxey. The proposed rock ramp is made up of strategically placed boulders and well graded rock as seen in Appendix A. In conjunction with the rock ramp, it is proposed that the adjacent section of river wall is strengthened and raised.
The Department is confident therefore, the design meets the requirements of IOM Strategic Plan General Policy 2.
6 Scoping Assessment for the Environmental Statement Paragraph 7.18.3 of the IOM Strategic Plan 2016 deals with the manner in which the Department will deal with applications which should be subject to EIA. The Department will adopt current practice on EIA’s from England and Wales set out in the publication “Environmental Impact Assessment: A Guide to Procedures”. However this has been superseded by The Town and Country Planning (Environmental Impact Assessment) Regulations 2017. Schedule 4 of these Regulations states that the following information is to be included in Environmental Statements: -
1. A description of the development, including in particular:
a) A description of the location of the development
b) A description of the physical characteristics of the whole development, including where relevant, requisite demolition works and the land use requirements during the construction and operational phases.
c) A description of the main characteristics of the operational phase of the development (in particular any production process) for instance energy demand and energy used, nature and quality of the materials and natural resources (including water, land, soil and biodiversity) used.
d) An estimate, by type and quantity, of expected residues and emissions (such as water, air, soil and subsoil pollution, noise, vibration, light, heat, radiation and quantities and types of waste produced during the construction and operation phases.
2. A description of the reasonable alternatives (for example in terms of development design, technology, location, size and scale) studied by the developer, which are relevant to the proposed project and its specific characteristics and an indication of the main reasons for selecting the chosen option, including a comparison of the environmental effects.
3. A description of the relevant aspects of the current state of the environment (baseline scenario) and an outline of the likely evolution thereof without implementation of the development as far as natural changes from the baseline scenario can be assessed with reasonable effort on the basis of the availability of environmental information and scientific knowledge.
4. A description of the factors specified in regulation 4(2) likely to be significantly affected by the development: population, human health, biodiversity (for example fauna and flora), land (for example land take), soil (for example organic matter, erosion, compaction, sealing), water (for example hydromorphological changes, quantity and quality), air, climate (for example greenhouse gasemissions, impacts relevant to adaptation), material assets, cultural heritage, including architectural and archaeological aspects, and landscape.
5. A description of the likely significant effects of the development on the environment resulting from, interalia:
a) the construction and existence of the development, including, where relevant, demolition works;
b) the use of natural resources, in particular land, soil, water and biodiversity, considering as far as possible the sustainable availability of theseresources;
c) the emission of pollutants, noise, vibration, light, heat and radiation, the creation of nuisances, and the disposal and recovery of waste;
d) the risks to human health, cultural heritage or the environment (for example due to accidents or disasters);
e) the cumulation of effects with other existing and/or approved projects, taking into account any existing environmental problems relating to areas of particular environmental importance likely to be affected or the use of natural resources;
f) the impact of the project on climate (for example the nature and magnitude of greenhouse gas emissions) and the vulnerability of the project to climate change;
g) the technologies and the substances used.
The description of the likely significant effects on the factors specified in regulation 4(2) should cover the direct effects and any indirect, secondary, cumulative, transboundary, short-term, medium-term and long-term, permanent and temporary, positive and negative effects of the development. This description should take into account the environmental protection objectives established at Union or Member State level which are relevant to the project, including in particular those established under CouncilDirective 92/43/EEC(1) andDirective 2009/147/EC(2).
6. A descriptionof the forecasting methods or evidence, used to identify and assess the significant effects on the environment, including details of difficulties (for example technical deficiencies or lack of knowledge) encountered compiling the required information and the main uncertainties involved.
7. A description of the measures envisaged to avoid, prevent, reduce or, if possible, offset any identified significant adverse effects on the environment and, where appropriate, of any proposed monitoring arrangements (for example the preparation of a post-project analysis). That description should explain the extent, to which significant adverse effects on the environment are avoided, prevented, reduced or offset, and should cover both the construction and operational phases.
8. A description of the expected significant adverse effects of the development on the environment deriving from the vulnerability of the development to risks of major accidents
and/or disasters which are relevant to the project concerned. Relevant information available and obtained through risk assessments pursuant to EU legislation such as Directive 2012/18/EU(3) of the European Parliament and of the Council or Council Directive 2009/71/Euratom(4) or UK environmental assessments may be used for this purpose provided that the requirements of this Directive are met. Where appropriate, this description should include measures envisaged to prevent or mitigate the significant adverse effects of such events on the environment and details of the preparedness for and proposed response to such emergencies.
9. A non-technical summary of the information provided under paragraphs 1 to 8.
10. A reference list detailing the sources used for the descriptionsand assessments included in the environmental statement.
Review of the requirements of Schedule 4, to create a scope for the Environmental Statement:
The broad range of detailed requirements for an EIA and Environmental Statements associated with development, set out above, was intended for much larger and more complex developments and, most likely, set in a more environmentally sensitive location. Not all of these items are of relevance to this development. This development concerns works to remove the weir structures and replace with a rock ramp weir made up of strategically placed boulders and well graded rock. The Department, through the steps outlined in Sections 4 and 5 demonstrates that it has met the requirements of Environmental Policy 10.
6.1 Biodiversity and nature conservation
An ecological impact assessment has been commissioned and consultations have been carried out with DEFA and its Fisheries Division. The Ecosystem Policy Officer will be contacted to clarify that there are no concerns from a wildlife and protected areas point of view.
The works could have the potential to have a number of environmental effects. Several of these effects are linked to risks during the construction phase. This is due to the close proximity of the scheme to the river environment, which will require some construction works to take place within the river. There is also a risk that construction activities could cause noise or visual disturbance to birds roosting or feeding in the area. However, the significance of such effects is low and would have a negligible impact for the duration of the proposed works when compared to the normal background noise conditions. It is possible that adverse effects on water quality and river ecology
could arise due to pollution during construction as a result of the accidental mobilisation of existing ground contamination. To mitigate this care will be taken to prevent sediment flowing downstream from the construction works. Netting will prevent some sediment flowing downstream of the river and bunds will be constructed to segregate working areas from the natural river flow.
These risks can be effectively managed through the implementation of good construction practice and through the development of detailed method statements that seek to protect the quality of the local environment including minimising noise generated by construction activities. The successful contractor will be required to provide a full Method Statement and Risk Assessments of all the activities involved in the replacement of the weir and these will all be agreed prior to commencing the works with the design engineer.
This project will reinstate the natural river conditions prior to the construction of the weir.
6.2 Water environment The removal of the weir could have temporary effects on water quality due to the release of contaminating construction materials or the mobilisation of existing potential ground contamination. However, the mitigation proposals already covered in section 6.1 of this report have already described how these effects can be controlled i.e. by use of netting and building.
6.3 Landscape and visual impact The proposed removal of the weir structures and replacement with a rock ramp weir will have negligible landscape and visual effects. It could be said that it will enhance the visual appearance of the Laxey River as the existing weir structure is in a poor condition with a large scour hole at the left toe of the weir and there is also steel reinforcement protruding from the concrete platform, with a further large scour hole on the left side of the channel.
The existing weirs reduce the riverbed level from 16.02mAD02 to 13.36mAD02 dramatically reducing the head level of the river whereas the proposed rock ramp aims to reduce the riverbed by the same amount but by utilizing a gradual gradient as advised by flood specialists JBA Consulting which will in turn help to alleviate flooding within Laxey. The proposed rock ramp is made up of strategically placed boulders and well graded rock which aesthetically should be more visually appealing than the existing concrete structures. Therefore, taking the above into consideration, we believe no further assessment is required on this matter.
6.4 Land and soil There is a small risk that construction activities could lead to mobilisation of contaminated materials in the ground, which could temporarily affect surface water quality. The proposed design minimises the requirements for excavation so there would be minimal disturbance to the existing ground conditions. Therefore, this risk is not considered to be of significance in this instance and we believe no further assessment is required on this matter.
6.5 Noise There is a slight risk that construction activities could have a temporary adverse effect on noise levels with the local areas. These effects will be effectively managed through the implementation of good construction practice and through the development of detailed method statements that seek to protect the quality of the local environment including minimising noise generated by construction activities. Therefore, taking this into consideration we believe no further assessment is required on this matter.
6.6 Climate Other than the usual emissions from vehicle movements to and from site and machinery used during the works, there are no climate damaging processes associated with this construction, or the operational phase of rock ramp when it is providing flood defence to the river and surrounding area. Therefore, taking this into consideration we believe no further assessment is required on this matter.
6.7 Material assets The completion of works in the removal of the weir structures and replacement with rock ramp can be considered to be a very important material asset for the future of the Isle of Man as it will protect the river from blockages and furthermore, the proposed solution will emulate the natural river, improving river continuity and fish passage. Therefore, taking the above into consideration, we believe no further assessment is required on this matter.
6.8 Population and local community The proposed works will provide increased protection from flooding for the community, therefore having a positive effect. The proposed solution will also have a permanent positive effect on the economy as it will increase protection for the area and reduce the risk of damage to the infrastructure and buildings. It will make homes at risk of being deemed uninhabitable secure for the future. Construction phase effects relate to temporary impacts on residents who may experience reduced amenity during the construction phase. This will be mitigated through consultation with stakeholders
and residents. Taking the above into consideration, we believe no further assessment is required on this matter is required.
7 Heritage and Conservation Areas The weir structures situated within Laxey River fall within the Laxey Conservation Area. A Conservation Character Appraisal has not been carried out of the Laxey Conservation Area, but this work will seek to repair and preserve the character of the existing wall structure in the area; with the replacement weir structures having been designed in a sympathetic manner.
There are multiple weir structures in the Laxey River adjacent to Glen Road that are in a poor condition and in need of replacing, and as such, leaving the structures as they are now would result in a great risk to the heritage and community of Laxey and to the properties which are situated along the riverbank as were the existing structures to fail, it could cause blockages downstream resulting in severe flooding. As has been seen in recent years, the flood risk is significant and likely to get worse due to climate change, so the surrounding area and adjacent properties are all at risk of significant harm or damage if nothing is done. In conclusion the applicant considers the design to satisfy IOM Strategic Plan Environmental Policy 35 because the proposals “preserve and enhance the character, and ensure that the special features contributing to the character and quality are protected…”
8 Conclusion In summary, the applicant believes this Statement of Case satisfies IOM Strategic Plan Environmental Policy 24 in addressing the salient points required by an EIA.
Furthermore, this report concludes that the existing weir structures should be removed and replaced in accordance with the proposal outlined in this Statement of Case as soon as possible to prevent any future flooding. The strengthening of the wall is to raise the original height to the same level as the new Glen Road wall to reduce the likelihood of future flooding. The proposed solution will emulate the natural river, improving river continuity and fish passage.
This is an important scheme for the residents of Laxey, protecting properties for the future against flooding, repairing dilapidation and securing the residential viability of the area through a period of climate change. It does this while protecting the visual amenity of the conservation area using sympathetic design.
9 Appendix A
9.1 Drawings
9.2 Photographs
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