Dunboyne Combined Residents Association
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Flooding in Dunboyne: 14th & 15th November 2002
Submission to Meath County Council: 30.01.03
Contents
The Flooding
Flood Facts
Statements From Residents of Flooded Estates
Meath County Council
National Response
Developers
Future Initiatives
Rights and Responsibilities
Engineering Aspects
Conclusion
Recommendations
Appendix: About DCRA
The Flooding
Approximately 130 houses and several business premises in Dunboyne were flooded on November 14th and 15th 2002. Clonee village houses and business premises were also severely flooded. The trauma for families affected was tragic and the damage done to their property and life style was devastating.
1. Newly built bridges over the River Tolka under the N3 too small to take
flood water.
2. A recent major housing development in Dunboyne was built on a flood plain.
3. Gutters and drains were blocked.
4. Castle River: 4 bridges not able to take water flow.
5. Tolka River: 3 bridges (excluding the N3) not able to take water flow.
6. Green Sawmills Bridge: wire causing built up of debris and blockage.
7. Drainage upstream good so flood waters reach Dunboyne within one hour of
rainfall.
8. Quarry at Bracetown: This natural flood over spill was filled in.
9. Since last flooding: Minor but inadequate cleaning of Castle River bed.
10. Dunboyne was inaccessible by all roads.
11. Professor Brian Cox: Flooding was almost entirely due to development.
Flood Facts
1. While flooding in Dunboyne can be primarily attributed to exceptionally heavy rainfall it must be noted that local developments were major contributory factors, especially those on flood plains, with the consequent reduction of soakage lands in the catchment area of the rivers and increased run-off from developed areas.
2. In contrast, it is readily demonstrated that a radical change has occurred in the performance of the Tolka, during periods of exceptionally heavy rain, between 1954, when no extensive developments in the catchment area and the destruction of flood plains had taken place, and the present day.
3. The two following reports contain the facts of the recent event:-
4. · Mac Cartaigh, M. Flooding in the Tolka Catchment 15 November 2002
Environmental Protection Agency
5. · Sheridan, T. Some information on the precipitation event around
14th November 2002. Irish Meteorological Services.
6. In the recent storm of 2002 some 80mm of rain fell in a 32 hour period. Over a catchment area of 138 sq. kilometres this is equivalent to an average downpour of some 96 cubic metres per second. The estimated peak flow in the river at Glasnevin was 98 cubic metres per second, indicating a runoff of around 100%.
7. In contrast, in the storm of 1954 some 63.5 mm of rain fell in a period of 17 hours. Over a catchment area of 138 sq. kilometres this is equivalent to 151cubic metres per second (54% higher than in the recent storm). However, the estimated peak flow in the river was only 85 cubic metres per second (12% lower than in the recent storm), giving a corresponding lower runoff of only 56%.
8. The massive increase in the runoff between 1954 and the present time cannot be attributed to the rainfall. It therefore follows that the extensive building in the catchment area together with the destruction of the flood planes must be largely responsible for the radically altered behaviour of the river and the damage to quality of life and property of residents caused by resulting flooding.
9. The Irish Meteorological Services report states that these storms are not dramatically exceptional, so that bearing in mind what is to be expected in a global warming scenario, one cannot exclude the possibility of even more sever storms in the foreseeable future. Indeed, one can only describe as horrendous the havoc that would have been caused had the 54% higher rainfall of 1954 storm occurred under present conditions instead of the actual one. Those responsible for providing the 'Environmental Protection' that is our right under the Maastricht Treaty are obliged to guarantee residents that they are effectively and transparently fulfilling their obligations.
10. Building and development include a whole variety of structures such as bridges, dams, tunnels, roads, culverts, housing estates and so forth. In this instance, the N3 and the bridges at Clonee, through which the Tolka flows, is of particular interest to residents of Clonee and Dunboyne. The estimate peak flow at Clonee during the recent storm can easily be deduced to have been of the order of 50 cubic metres per second. There is clear evidence on site that the bridge is not designed for a flow of this magnitude. It is certainly not designed to cope with the much greater downpour of 1954 which would result in a peak flow of some 75 cubic metres per second under present conditions. In which case the N3 would simply act as a dam downstream of two villages of Dunboyne and Clonee with devastating consequences.
Statements From Residents of Flooded Estates
1. Larchfield
Larchfield residents, along with so many of our Dunboyne neighbours, were shocked to have been flooded again two years after the last episode. The flood in 2000 was, depending on the expert one spoke to, meant to have been a one in twenty or fifty-year event.
Very little, if indeed any, meaningful heavy-duty work appeared to have been undertaken in the intervening two years to minimize future potential risk in obvious high-risk areas. Much appears to be dependent on the forthcoming Consultants report. Although it really is 'too little, way too late', it is hoped the immediate requirements which will be listed in this interim report to alleviate damage potential in the worst affected areas will be immediately acted upon.
People in Larchfield are angry. Many are disillusioned with the whole political scene and the fact that further planning permission matters are even being processed in areas which can only exacerbate the whole flooding/drainage issue. A sensible and surely obvious stop should be placed on all planning matters until a proven solution is in place.
There is a solution to this problem, just as one was found and implemented in the Lucan area. We look forward to Dunboyne being given a similar and immediate sense of priority. More importantly however, we look forward to this issue being maintained as the number one item on any agenda until successfully addressed. In the meantime we are exploring all avenues to ensure a productive focus is maintained.
2. Beechdale
Beechdale estate was built in the late seventies/early eighties on land that locals knew to be prone to flooding. This was information that only came to the attention of residents after flooding occurred. In 1986 there were approximately 8 houses flooded in the aftermath of Hurricane Charley. The height of the floodwater was approximately an inch inside the affected houses.
In the years afterwards the residents were vigilant in trying to ensure that adjacent lands would not be built on in their own interests and that of prospective homes owners in the future. In the late eighties the
N3 was constructed. Subsequently numerous developments were undertaken increasing significantly the number houses in the area. Other major drainage projects on farms, sports grounds and notably stud farms took place in the vicinity, apparently without any intervention from the local authority. This has reduced the amount of land available to take soakage and floodwater and increased the rate of flow-off into the waterways.
In 1996 objections were made to a number of developments, objections that were ignored resulting in catastrophic consequences. In 2000 approximately 24 houses were flooded to a height of up to 19 inches inside the houses. In 2002 these and more houses were affected, this time taking the level of water to up to 26 inches.
We now wish to make known our continued objections to further large scale rezoning for development for housing or industry. The time has come to put a stop to this careless and irresponsible development and expansion of Dunboyne. Instead there is a need to take measures to reverse the effects of the reckless behaviour of the past.
Meath County Council
1. Ill-advised and irresponsible planning has had a major part to play in the flooding of Dunboyne. Building on flood plains and on natural drainage areas has aggravated the problem.
2. Larchfield estate was built on a flood plain despite objections and advice from the community. Meath County Council acted irresponsibly not only by allowing the flood plain to be destroyed for no compelling reason but also for failing to provide an equivalent alternative facility.
3. Beechdale estate was more severely flooded because Larchfield estate was built and because the river bank at the Larchfield side of the river was heightened.
4. DCRA has failed to find any mention of the flooding risk issue in Dunboyne in the records of Meath County Council meetings leading to the preparation of the County Development Plan 2001.
5. Repeated submissions by DCRA to MCC towards the preparation of the Meath County Development Plan 2001, that because of flood risk in the area, land for further developments should not be rezoned. MCC however ignored this and rezoned 90 acres of land for residential development of approximately 2,500 dwellings. 250 acres of land was also rezoned for an Industrial Estate together with the potential rezoning of an additional estimated 50 acres for housing development at Clonee. This was ironically agreed in March 2001 approximately four months after the severe flooding in Dunboyne in November 2000. Furthermore it should be noted that 43,000 square metres of building development and car park of 2,300 car spaces are in the planning stage just down stream at Mulhuddart on the N3 all of which will have an upstream affect on Clonee and Dunboyne flooding and of course down stream.
6. Because bad planning is a major contributor to the current flooding situation in Dunboyne then the County Council must accept a degree of responsibility for compensation to those whose property has been damaged.
National Response
1. People whose homes and livelihoods have been ruined by flooding obviously need compensation, and it is advisable that the State be involved if insurance premiums are to be kept within reach.
2. In instances where the insurance agencies refuse cover for houses affected by flooding or quote premiums that are not affordable then the State should intervene and if necessary provide insurance coverage direct.
3. A national body with statutory responsibility for flood management should be established to reverse the trend of casual and inadequate regard to citizens' environment. This is an urgent and necessary requirement.
4. The State must show due regard for the rights of its citizens by developing over the coming years strategic planning enforceable guidelines for all river catchments. These plans are fundamental to the long term upgrading of flood defences to take account of local conditions, existing risks and defences, and the impact of changes in sea level, climate and rainfall.
5. Maps indicating flood risk in all areas in the country are now self-evidently required to protect citizens' investments in property and their living environment. Planning maps of areas within one kilometre of rivers should show contours at five metre intervals.
Developers
1. To consider how the costs of flood prevention and protection may be shared by developers.
2. The onus must be placed on developers to provide detailed assessment of flood risk and submit a hydrological survey as part of a planing application
3. Developers should not be allowed to interfere with flood plains under any circumstances.
4. If flood defences are not put in place by developers and subsequent flooding occurs then the developer must be held responsible.
Future Initiatives
1. Recent floods have raised concerns that further and inappropriate development in the flood plain will lead to more extensive flooding.
2. Surveys to clarify where remedial work is required and where defences in areas of risk do not provide the level of safety to which residents are entitled.
3. It is essential that people whose properties could be affected by flooding are aware of the dangers, that they know what to do in an emergency, and that they know who is responsible for defence measures.
4. All of the bodies and agencies involved in flood defence work must work together to ensure that the complicated arrangements and sharing of responsibility is co-ordinated.
5. All available information on flood defence and flood barriers must be considered when working towards a solution. Flood defence structures include sluices, weirs, barriers, locks, outfall culverts and pumping stations. Linear barriers are walls, barriers and embankments between the river and defended areas.
6. Forecasting, warning, protection and flood risk information are essential
elements of risk management both for Meath County Council and residents.
7. Responsibility for flood defence and information are fundamental obligations of Meath County Council and an entitlement of residents as of right.
8. Meath County Council must now take fully into account environmental issues and changes which can occur in flood risk areas as a result of new developments.
9. Meath County Council must decide the methods they will employ in future to warn residents of imminent flooding.
10. The efforts made by County Council staff and emergency services are appreciated. However, this recent incident calls for a review of emergency services, their adequacy, co-ordination and resourcing.
Rights and Responsibilities
1. What has been experienced by residents affected by the floods in Dunboyne
is an infringement of their rights.
· In respect of their person and families amounting to a traumatic psychological
impact on their wellbeing.
· In respect of their wealth and property serious erosion and damage.
· Thirdly there has been damage to their environment. They have a right
to live in an environment that is not threatening, an environment that does
not militate against the quality of their lives.
2. As fundamental as the rights of its citizens are the responsibilities of the State in ensuring those rights
· National and Local Government has the responsibility for the wellbeing
of citizens. That responsibility is underpinned by our Constitution (Article
40.3.2 & Article 45.4.2), the European Convention on Human Rights (Article
8.1), International Law and the International Treaties signed on our behalf
by the State.
· Dunboyne is an instance where the State has failed its citizens.
· Not only has the State failed in this instance, it has in fact contributed
proactively to that failure.
3. Consequently there are two major obligations on the State:
· To repair all damage done and immediately to undertake work to ensure
this flooding will nor happen again.
· To negotiate with residents with a view to compensating them fully
for what has happened because in no way was it their fault.
Engineering Perspectives
To begin, a few basics facts from an engineering point of view firstly are in
order by way of background. Firstly, one must distinguish between the hydrologic
and hydrodynamic aspects of the study of river flooding. In simple terms the
hydrologic aspect is concerned with matters relating to he rainfall and all
factors that affect the flow of water from where it falls until it reaches the
river. The hydrodynamic aspect is concerned with the flow of water down the
river once it has arrived there.
1. Hydrological Aspects
Automatic flow measurements in the Tolka are made at Glasnevin so that all flows
mentioned below unless otherwise stated refer to the flow measured at Glasnevin
station.
The average flow at Glasnevin is below the 3.5 m3/second that is equivalent
to the annual rainfall of 800 mm on a catchment area of 140 km2. It is termed
base flow and represents the level that one would expect in the absence of a
surface run-off.
Flash floods are caused entirely by rapid surface run-off. However this does
not necessarily mean that run-off accounts for the total rainfall of a given
event.
For example in the 2002 event some 87% of the total rainfall amounting to some
10 million cubic meters actually flowed down the river. The remainder found
its way down to the water table to join the base flow. On the other hand, some
80 mm of rain fell in a 32 hour period over a catchment area of 138 sq. kilometres.
This is equivalent to an average downpour of some 96 cubic metres per second.
The recorded peak flow in the river in at Glasnevin was 98 cubic metres per
second, indicating a runoff of around 100%.
In comparison in the case of the 1954 event- the only one for which I have comparative
figures - 63.5 mm of rain fell in a period of 17 hours. Over a catchment area
of 138 sq. kilometres this was equivalent to 151 cubic metres per second (54%
higher than in the recent storm). However, the estimated peak flow in the river
was only 85 cubic metres per second (12% lower than in the recent storm). The
corresponding runoff was only 56%. Unfortunately, there is no data to enable
the total volume of the run-off to be calculated, but it is likely, on the evidence
that the percentage by volume was of the same order.
In the present study, which must surely involve modelling the process, a major
aim of the hydrologic study will be to produce a number of hydrographs giving
the flow rate of water into the river as a function of time. The hydrographs
will then be used as the basis for the hydrodynamic model designed to simulate
the behaviour of the river for a number of scenarios involving flood reducing
measures.
Changes in land use such as from agricultural to urban development greatly increase
the rate of surface run-off and the consequent risk of flooding. The run-off
coefficient for urban area ranges from 0.50 to 0.95 compared to 0.05 to 0.25
for farmland.
2. Hydrodynamic Aspects
In the two recent events, the extent of the flooding at both Dunboyne and Clonee
by all reports was far more extensive that at any previous time.
In the 2002 event not only were all the bridges over the two rivers in the district
fully submerged but also there is clear evidence that the water rose to about
one meter above the soffit of the bridge over the river on the N3 at Clonee.
The total cross section area of the opening beneath the bridge is only 22.5
m2 (9.0 meters wide x 2.5 meters high). Even if the structure was designed to
operate as a submerged culvert, a cross section area of 22.5 msq is hopelessly
inadequate for a predictable flow of the order of 45 sq./second readily deducible
from the 1954 data. Although, it could hardly have been envisaged that the soffit
would become submerged at any stage, this area is hopelessly inadequate for
a predictable flow of the order of 45 m3/second based on the 1954 data. Indeed
it is difficult to believe that any reasonable consideration was given to the
peak flows at Clonee when deciding the dimensions of this bridge. A prudent
engineer, being in possession of the relevant flood data would have certainly
decided on a width of at least double the existing one.
There is a dramatic difference between the hydrodynamic behaviour of a bridge
under normal conditions and when the inlet becomes submerged. Under the latter
conditions the structure behaves as a culvert.Moreover, at the precise moment
when the water level reached the soffit of the bridge, conditions would have
switched instantaneously. The result would have been what is described as 'choking'.
It is likely that a wave would have formed caused by the sudden rise in water
level due to increased friction. It is likely that the wave would have been
propagated upstream where it could have adversely affected the flow from the
bridge under the old railway line at Dunboyne. This could easily have triggered
a similar affect from one bridge to the next. The bridges around Dunboyne were
all submerged during the last event and from the study of flood levels taken
after the 2000 event it is almost certain that they were also submerged then.
The above hypothesis can easily be tested by comparing the hydrodynamic behaviour
of the river under present conditions and those that prevailed prior to the
construction of the N3. All the necessary information regarding cross section
profiles must be available from the construction drawings.
In view of the flooding all along the Tolka in 2002 and in view of the findings
in relation the Clonee bridge it is likely that all the other bridges involved
in the N3- and there are at least eight new bridges associated with it and its
link roads - caused similar restrictions to the flow and were primarily responsible
for the flooding along the valley.
3. Measures
Ball park figures can be estimated from the flood in 2002 that serves to illustrate
the good sense of a policy of retention as opposed to one of "flushing"
as a sensible measure to reduce flooding.
The total volume (run-off) involved was some 10 million m3. Of this it is estimated
that about one million m3 or some 10% was actually retained by the flooding
all along the valley from Dunboyne to Glasnevin. This temporary storage served
to reduce the peak flow at Glasnevin and consequently the extent of flooding
that would otherwise have occurred in the city area. It is easy to show that
the potential peak flow might have been as high as 120 m3/second, that is some
40% above the existing design capacity (85 m3/second) of the river d/s of Glasnevin.
The catchment at Clonee is 70 km2 or almost exactly half that at Glasnevin so
half the water that flows past Glasnevin clearly comes from the catchment upstream
of Clonee. In the 2002 flood, this amounted to about 5 million m3 and the peak
flow could have been a high as 60 m3/second.
The cost of modifying the river bed and associated structures to cope with flows
ranging from 60m3/second at Clonee to 120 m3/second at Glasnevin would clearly
be many times greater than for providing reservoirs upstream of Dunboyne, Clonee
and Mulhuddard needed to store the one million m3 estimate d above plus say
another half million m3 required to reduce the recorded peak flow of 98 m3/second
to below the design flow level of 85 m3/second.
The problem must be addressed on a catchment wide basis rather than in a piecemeal
fashion. Moreover the future management of the Tolka Catchment must be given
to a single Authority with responsibility of implementing a well-defined policy
designed to reduce the risk of flooding. The control of land use in sensitive
areas must be taken out of the hands of those with conflicting interests and
require to comply with flood risk policies.
4. Extracts from HR.Wallingford's Newsletter #6.
· 'A policy of "keeping the water where it falls" should be
an important aspect of flood risk management. Watershed management and environmental
conservation practice in flood risk areas includes appropriate land-use planning
in order to store floodwater and to control the inundated areas'
· 'River engineering measures (reinforcement of levees, dikes, dams, reservoirs etc.) can modify the depth, volume, and velocity of the flood. The influence of linear infrastructure, such as roads, railways or pipelines and the discharge capacity of bridges need to be examined.'
· 'Effects of reservoirs in upstream areas can be important. Flood storage in the Czech Republic was shown to be effective in reducing the downstream peak flow of the first Odra flood wave'
Conclusion
1. DCRA has recently responded to two Integrated Area Action Plans issued by
Meath County Council
2. where flooding issues were inadequately addressed and the matter not given
due regard.
3. It was a travesty of democracy that the Local County Councillors despite all the evidence and against the massive recorded objections of the vast majority of the Dunboyne community voted excessive rezoning of lands in Dunboyne and adjacent to it contrary to the Strategic Planning Guidelines for the Greater Dublin Area.
4. The flooding in Dunboyne now, and again two years ago, has raised serious concerns that further or inappropriate developments in Dunboyne will lead to more frequent and extensive flooding. DCRA therefore must assert in the strongest terms possible that the proposed developments on the recently rezoned lands in Dunboyne, as per MCC Development plan 2001, especially those east of the railway line and in Dunboyne Castle Grounds must not be approved.
Recommendations
1. That no further development take place in Dunboyne and Clonee until the flooding problem is solved to the satisfaction of residents.
2. That Meath County Council review its County Development Plan 2001in the light of recent flooding.
3. Lands that were rezoned in the County Development Plan 2001 which are liable to flooding or whose development will contribute to future flooding should now have their current zoning reversed to their previous zoned status.
4. That an enquiry be set up into the zoning of lands for development and the granting of planning permissions in Dunboyne and Clonee since 1990.
5. That because Meath County Council and others are significantly responsible for flooding in Dunboyne and Clonee that compensation be made to residents whose houses were flooded and to those whose houses were not flooded but the value of which has been affected and are liable to increased insurance premiums.
6. There should be an integrated policy, aimed to prevent or reduce accumulated peaks in water supply to flood-prone area along the Castle/Tolka Rivers by increasing the water retention in upstream parts of the rivers' system and/or in the surrounding uplands. To this end :
7. Two overspill and flood control lakes/reservoirs should be located one west of Dunboyne and the other between Dunboyne and Clonee villages.
8. The establishment of designated green belt areas.
9. That lands East of the disused railway line in Dunboyne be retained as natural soakage and should not be rezoned for development.
10. The management of land use in the catchment areas of rivers with a view to its potential for water retention.
11. That serious consideration be given to the establishment of new flood plains, the enlargement of existing flood plains and the creation of wetlands.
12. The retention of existing hedgerows and the development of new hedgerows and forestation in the catchment areas of the rivers.
13. That work now required to be carried out on the Castle and Tolka Rivers should not only be remedial but creative resulting in environmental improvements and leisure and amenity provisions for local communities.
14. That all future purchasers of property be given, as of right, a flood risk legal notification.
15. That the Minister for the Environment and Meath County Council ensure that 'liable to flooding' notices are included on all development maps.
16. Industries along the catchment areas of the Tolka/Castle Rivers that have use for non-potable water should be supplied from these rivers.
17. That responsibility for the maintenance of the Tolka and Castle Rivers be vested on one authority.
18. A land use planning policy and guidelines should be established in order to prevent development/building on flood-prone areas or developing infrastructures along watercourses.
19. That Developers be held responsible and liable as per section "Developers" above.
20. A review of emergency response services should be undertaken to ensure ability to respond, adequacy of resources, training and co-ordination.
21. A flood warning system for the benefit of residents should be put in place.
22. That all rezoning of lands for development in the catchment area of the Tolka and Castle rivers be dependent on a prior hydrological survey submitted to a competent and designated national body whose approval would be necessary.
23. That Dunboyne and Clonee be a Flood Risk Free Area by January 2004.
End 30.01.03
Appendix
About DCRA
Objectives
1. To inform, consult with and represent the residents of Dunboyne on issues affecting their quality of life and environment.
2. To monitor all planning applications in the Dunboyne area.
3. To take on board matters raised by any affiliated association.
4. To give collective support to affiliated associations.
5. To monitor and respond to all development plans proposed for Dunboyne to ensure that they are in compliance with county, regional, national and European planning laws and directives.
6. To work with residents associations in neighbouring counties within the Eastern Region.
7. To liaise with National Government Departments when needed.
8. To work with, negotiate with and remain in regular contact with Meath County Council.
9. To publish regular newsletters and maintain a DCRA website.
10. To protect and promote our local cultural and social heritage.
11. To protect, maintain and develop our landscape and environment.
Principles
1. DCRA exists to address and voice the interests and concerns of residents in line with the principle of Subsidiarity of the European Union (Maastricht Treaty) which states that decisions should be taken by the people most affected by them.
2. DCRA exists to preserve and develop the environment of residents in compliance with the principle of Sustainable Development as enshrined in Agenda 21 of the United Nations which requires that all development must serve not only economic objectives but also social and environmental objectives.
Membership
At present there are 21 Residents Associations in membership, representing 1,600 plus households and approximately 85% of the population of Dunboyne.