Resilient infrastructure Tools to assess infrastructure performance in the face of coastal erosion and flooding

Transcription

1 March 2016 Cathal Mangan Resilient infrastructure Tools to assess infrastructure performance in the face of coastal erosion and flooding Emer Kennedy Susana Lizondo

2 Contents Background & aims Irish Rail context challenges of the 2015/2016 winter floods Overview of research: Development of a strategic flooding analysis method for critical railway/water interface zones Medium to long term management options for coastal protection of railway infrastructure Conclusion Discussion

3 Background & Aims

4 Background and Aims Arup funded research project Collaboration with Iarnród Éireann Aims Develop tools for assessing vulnerable areas across Irish Rail network for: Coastal erosion Flooding

5 Irish Rail context Challenges of the 2015/2016 winter floods

6 Irish Rail: challenges of winter 2015/2016 floods

7 Overview of Flooding Impacts on IÉ 2015/16 Enniscorthy: track and station flooding

8 Overview of Flooding Impacts on IÉ 2015/16 The Murrough, Wicklow: Coastal erosion

9 Overview of Flooding Impacts on IÉ 2015/16 Mayo Line: pluvial flooding

10 Overview of research

11 Development of a strategic flooding analysis method for critical railway/water interface zones Emer Kennedy Arup

12 Study Area Bray to south Greystones Beach Mountainous Agricultural lowland Urban Assessment included pluvial and fluvial sources of flooding i.e. rainfall runoff and watercourse flooding

13 Methodology Develop a methodology for the rapid assessments of large sections of the rail network that can be replicated across Irish Rail network Desktop Study Targeted site visit Assessment Analysis & Outputs Comparison with coastal research

14 Methodology Strategic Flooding Research 1. Desktop Study Review of information available publically Office of Public Works CFRAMS & Historical information MET Eireann rainfall Review of information received from Irish Rail Culvert inspection records Surveys rail & existing utilities Review of external catchment topography (source: OSI) Identification of potential flood mechanisms 2. Targeted site visit

15 Methodology Strategic Flooding Research 3. Assessment Hydrological assessment Hydraulic assessment 4. Analysis & Outputs Risk assessment Prioritisation 5. Comparison with coastal research

16 Hydrological Assessment External Catchments Inflows at rail corridor/ adjacent land interface Assessment criteria defined 10% AEP (1 in 10 year ARI storm) 3.3% AEP (1 in 30 year ARI storm) 1% AEP (1 in 100 year ARI storm) Review of soil type FSR mapping Estimation of catchment runoff Catchment < 0.4km 2 : ADAS method Catchment < 25km 2 : IH124 method Catchment > 25km 2 : FSU Webportal application

17 Hydraulic Assessment External Catchments Culvert capacity assessment High level Excel Spreadsheet Criteria: headwater above culvert soffit or rail level - further assessment required On track & track side ponding identified through Floodflow analysis Indicative of trapped catchments / culvert requirement

18 Hydraulic Assessment External Catchments Culvert capacity assessment Criteria: headwater above culvert soffit or rail level - further assessment required

19 Hydrological Assessment Rail Corridor Recurrence Interval 10 year (mm) (mm/hr) Location: Greystones 30 year (mm/hr) (mm) 100 year (mm) (mm/hr) Duration 5 mins mins mins mins hours hours hours hours hours hours hours hours hours days days days days days days days days days days Preparation of storm intensity from Met Éireann information Consideration of climate change Generate hydrograph using Floodflow analysis

20 Hydraulic Assessment Rail Corridor FloodFlow analysis Low impact: 100mm (red band) Medium impact:300mm (yellow band) High impact:600mm (white band) Consideration of ballast depth & void ratio to determine actual ponding depth

21 Priority/Risk Assessment Potential Issues Restricted rail services Stoppage to rail services Ingress of fines into ballast Sleeper and ballast degradation Erosion of track formation Ballast fouling Identification of underperforming assets Identification of areas where stormwater asset required

22 Potential issues: ballast washout Kiltartan, Limerick to Galway line: flooded track, undermined by wash-out of ballast and collapse of culvert beneath track

23 Potential issues: sink-hole Limerick to Waterford line: ballast failure

24 Potential issues: landslide Landslip on Kerry line at Killeen

25

26

27 Conclusions & Recommendations Further investigation to determine/confirm existing assets Development of an asset register sample provided Further development of the existing IE GIS database to include georeferenced stormwater asset information Implement study methodology on future assessments

28 Medium to long term management options for coastal protection of railway infrastructure Susana Lizondo Arup

29 Introduction Many coastal areas of Ireland under threat from future erosion Segments of IE s network are in these areas Increasing need for long term sustainable and environmentally friendly solutions This study aims to promote this concept with a methodology that can be applied to these areas

30 Flooding 2015/16 Coastal Erosion, The Murrough, Wicklow Photo shows the scale of the coastal erosion directly adjacent to previous installed protection measures

31 Flooding 2015/16 Coastal Erosion, The Murrough, Wicklow Photos show the rapid erosion of the coastline from November 2014 to December 2015

32 Methodology Data collection Workshop with IE Site visits Assessment of information Assessment of suitable solutions

33 Study area overview Workshop with IE to determine the study area: conclusions Area between Bray Head and Greystones South Beach was selected A large number of IE coastal defence assets exist in the area Previous information available for the area Arup familiarity with the area Study area divided into 3 zones

34 Bray Head 3km of railway line on a steep cliff Vulnerability to coastal processes Historical erosion and relocation of the railway line Several IE coastal defence assets Upgraded with revetments in 2002

35 Greystones North Beach 2.5km of railway line veering up to 200m inland No immediate threat to railway line ICPSS maps indicate potential danger by 2050 Arup monitoring of the beach indicates localised erosion in the order of up to metres per year Historical groynes used at the beach

36 Greystones North Beach Evidence of erosion during site visit

37 Greystones South Beach 5km of railway line from Greystones to 20MP Problems in the past with overtopping and erosion of embankment Relocation of the line in 1912 IE maintaining coastal defence assets on route ICPSS maps indicate erosion

38 Coastal processes and climate change Bray Head

39 Coastal processes and climate change Greystones North Beach

40 Coastal processes and climate change Greystones South Beach

41 Coastal solutions A number methods exist to combat coastal erosion and flooding Can be divided into offshore, lower shore and near shore They have varying environmental impacts Method suitability dependant on a number of site related factors

42 Selection of feasible solutions Offshore wave climate Hs=f(Tr) Nearshore propagation: Mike 21 SW model Tr= 1, 10, 50, 100, 200 and 1000 years Tides and surge levels Climate change level rise Littoral sediment transport Geology, physical boundaries, etc. Functional requirements.

43 Options assessment A shortlist of options generated from database of coastal solutions Options assessed based on the following criteria: Site specific application Public safety consideration Cost of design life and maintenance Practicality in construction Environmental friendliness Licensing and permits Adaptive capacity to climate change Impacts on adjoining areas Criteria Scoring Options assessment

44 Environmental Considerations

45 Planning consent and licensing Due to the environmental sensitivity of the study area the following may be necessary depending on the proposed solution: Appropriate Assessment (AA) Screening Environmental Impact Assessment (EIA) Screening Planning consent Foreshore licence Extensive consultation with government departments Other considerations to be considered such as archaeological and architectural features, protected views, sensitive landscapes etc.

46 Shortlisted options Bray Head Greystones N.B. Greystones S.B. Upgrade existing revetment Groynes Upgrading existing revetment New revetment (rock armour) New revetment (concrete) Offshore breakwater Seawall Offshore breakwater Beach nourishment and managed retreat Groynes with beach nourishment Partial revetment with beach nourishment Revetment with beach extension and nourishment Gabions with beach extension and nourishment Artificial sand dunes with beach extension and nourishment Segmental offshore breakwater and nourishment Groynes and beach nourishment

47 SCORING Site specific application Public safety considerations Cost in relation to Design life and maintenance Practicality in construction Environmentally friendly Licensing and Statutory Permits Climate Change resilience Impacts on adjoining areas Multi-criteria assessment Greystones North Beach - Scores 1 OPTIONS Extreme Risk - Success Improbable CRITERIA 2 Success Unlikely 3 Average Risk 4 Success Likely 5 Low Risk - Success Probable WEIGHTING Option 1 Groynes Option 2 Offshore breakwater Option 3 Beach nourishment and managed retreat Option 4 Groynes with beach nourishment Option 5 Partial revetment with beach nourishment

48 SCORING Site specific application Public safety considerations Cost in relation to Design life and maintenance Practicality in construction Environmentally friendly Licensing and Statutory Permits Climate Change resilience Impacts on adjoining areas Total Ranking Multi-criteria assessment Greystones North Beach Scores by Weights OPTIONS CRITERIA 1 Extreme Risk - Success Improbable 2 Success Unlikely 3 Average Risk 4 Success Likely 5 Low Risk - Success Probable WEIGHTING Option 1 Groynes Option 2 Offshore breakwater Option 3 Beach nourishment and managed retreat Option 4 Groynes with beach nourishment Option 5 Partial revetment with beach nourishment

49 Results Bray Head area Greystones North beach Greystones South beach Upgrading existing revetment Functional requirements met Cost effective Minimum licensing and permits Partial revetment with beach nourishment Functional requirements met (hold the line) Environmentally friendly Practical to construct Revetment with beach extension and nourishment Functional requirements met (railway line protected from wave action) Environmentally friendly No impacts in adjoining areas

50 Conclusion and recommendations

51 Conclusion and recommendations Arup highlights the importance of this climate change in any decisions made by IE for future design works to ensure resilient infrastructure. To develop existing IE GIS database to include information on stormwater, flooding and coastal defence assets. Holistic approach needed to fully assess the interactions and interrelations between the different constraints and solutions for each area. The same methodology could be applied to other areas Development of a national strategy for coastal erosion management

52 March 2016 Cathal Mangan Thanks for your attention! Questions? Emer Kennedy Susana Lizondo