Presentation on Flood Risk Management To Engineers Ireland 12 th February David Keane Cork County Council

Transcription

1 Presentation on Flood Risk Management To Engineers Ireland 12 th February 2014 David Keane Cork County Council 1

2 Contents 1. The Power of Water 2. Defenses 3. Flooding & Flood Types 4. Flood Mitigation Schemes in Cork County 5. Case Study 2

3 Constructive Power of Water Essential for our very survival 3

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6 Victoria Falls 6

7 Destructive Power of Water The power of water can be catastrophic 7

8 Tsunami In Sendai March 11 th

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10 Howth Co. Dublin 10

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25 Flooding The guidelines for Planning Authorities define flooding as a natural process that can occur at any time and in a wide variety of locations. Flooding is a natural event. 25

26 Flooding There was a time when rain fell on either permeable or impermeable ground but the balance was right and the infrastructure was capable of getting this rainfall to the desired water course and that water course was capable of dealing with it. 26

27 Not so now The area of impermeable ground has increased considerably and there is a greater catchment that has direct runoff to the water course. Rainfall intensity and duration has increased so that the remaining permeable area becomes saturated very quickly and this area now contributes to almost complete runoff leading to an overwhelming of the water course. 27

28 Types of Flooding in Ireland 1. Flooding due to Pluvial Events 2. Flooding due to Fluvial Events 3. Coastal Flooding due to Tidal events 4. Flooding due to a combination of any of the above 28

29 Pluvial Pluvial flooding can be defined as flooding that results from rainfall-generated overland flow, before the runoff enters any watercourse or sewer. It is usually associated with high intensity extreme or monster rainfall events (typically >30mm/h) resulting in overland flow and ponding in depressions in the topography. In urban situations underground sewerage/drainage systems and surface watercourses may be completely overwhelmed. Fluvial Flooding that results from discharge from a water course Coastal Flooding Flooding that results from discharge from tidal waters 29

30 Coastal Flooding Based around the Astronomical high tides Largely predictable, relatively short duration Influence by Spring tides. Prevailing winds gales will raise the tide up to 1 metre. Low atmospheric conditions. 30

31 Other influences Climate change Global warming Climate change effects suggest that the frequency and severity of flooding is likely to increase in the future. 31

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33 November 2009 Flood 33

34 Summer 2012 Flood 34

35 Contents CORK COUNTY COUNCIL SCHEMES In conjunction with the OPW (or more correctly OPW in conjunction with CCC) Categories: Major Schemes Minor Works / Studies River Cleaning / Others 35

36 Generally for major schemes this is a 5-Stage Process. Stage 1: Feasibility & Preferred Option Selection Stage 2: Environmental Assessment & Planning Stage 3 Detailed design, tender process & award of construction contract Stage 4: Construction Stage 5: Handover Gives rise to a substantial time lag - 3 to 5 years 36

37 Major Schemes / Studies CCC Major Schemes / Studies 1. Mallow Flood Relief Scheme 2. Fermoy Flood Relief Scheme 3. Bandon Flood Relief Scheme 4. Skibbereen Flood Relief Scheme 5. Clonakilty Flood Relief Scheme 6. South-Western, South-Eastern, Shannon Catchment Flood Risk Assessment In excess of 120M 37

38 Mallow Flood Relief Scheme Value (approx) 36.7m Lead Organisation Full OPW scheme. CCC on steering group. Consultant Arup Update Phase 1: Mallow North - Operational. Phase 2: Mallow South and West - Handover. Mallow (North) BEFORE Mallow (North) AFTER 38

39 Fermoy Flood Relief Scheme Value (approx) 37.8m Lead Organisation Full OPW scheme. CCC on steering group. Consultant T.J. O Connor Update Phase 1: North - Fully operational scheme. Phase 2: South - Major civil engineering works have commenced. The current contract programme is scheduled to finish April 2014 Fermoy Fermoy 39

40 Bandon Flood Relief Scheme Value (approx) 9.6m Lead Organisation Full OPW scheme. CCC on steering group. Consultant Byrne Looby Partners (formerly WYG) Update Currently at Stage 3: Detailed Design, Tender & Procurement. The main Flood Relief Scheme in-channel works (dredging) is currently programmed to commence in 2014 (1 May 30 September). Scheme includes 3.6km of dredging and some walls and embankments in the town. Main part is the dredging. Expected to take 2 summer periods. 40

41 Skibbereen (River Ilen) Flood Relief Scheme Value (approx) 10m Lead Organisation CCC acting as OPW Agents. CCC procured the design consultant and channel floodplain surveyor (both funded under Minor Works Programme). OPW on steering group. Consultant Update RPS for study and Murphy Surveys for channel floodplain The Consultants are currently progressing through to tender stage, expected to go to tender in april 2014 Contactor due on site in 3 rd. Quarter in

42 Clonakilty* Flood Relief Scheme Value (approx) 7m Lead Organisation OPW project under the South Western CFRAM. CCC on steering and progress group. Consultant Mott MacDonald Update Clonakilty has been accelerated in the South Western CFRAM Study. Tender for Consultants for design stage just advertised. (*under South-Western Catchment Flood Risk Assessment and Management Scheme 42 (CFRAMS))

43 South-Western, South-Eastern, Shannon CFRAM Catchment Flood Risk Assessment and Management. Study to give an overall plan and meet national requirements Full OPW scheme. CCC on steering and progress groups. Mott MacDonald for South-West, RPS for South-East, Jacobs for Shannon The National CFRAM programme commenced in Ireland in The CFRAM Programme comprises three phases: 1. The Preliminary Flood Risk Assessment (PFRA): The CFRAM Studies and parallel activities: Implementation and Review: 2016 onwards The first step, the PFRA, to identify areas at risk of significant flooding, has been complete. The next step is the CFRAM Studies and, to implement this, the country has been split into 6 regions (CCC is involved in 3 regions): 1. Shannon (Milford & Charleville) 2. South-East (Carrigmore, Mitchelstown) 3. South-West (remainder of CCC) 4. West 5. North-West / Neagh-Bann 6. East 43

44 Minor Works / Studies Glanmire/Sallybrook (Glashaboy River) Flood Risk Assessment and Management Study Crookstown, Douglas, Togher Flood Risk Assessment and Management Studies Carrigtwohill Flood Risk Assessment The Glen in Passage West Study and Remedial Works Riverstick and Environs Flood Relief Scheme 44

45 Glanmire/Sallybrook (Glashaboy River) Flood Risk Assessment and Management Study Value (approx) 1m Lead Organisation CCC acting as OPW agents. CCC to procure the Engineering Consultants. Consultant Preferred bidder Update This area was investigated in the Lee CFRAMS and works were suggested. Following the June 2012 event, the works were advanced ASAP. Consultants appointed

46 Crookstown, Douglas, Togher Flood Risk Assessment and Management Studies Value (approx) Lead Organisation CCC acting as OPW agents. CCC to procure the Engineering Consultants. Consultant Preferred Bidder Update Study to follow immediately after Glanmire/Sallybrook brief is finalised. Once Consultant is appointed, timeframe is estimated to be the same as Glashaboy. Crookstown and Togher were investigated in the Lee CFRAMS and works were suggested. The Douglas area was looked at but no works were suggested in the Lee CFRAMS. Following the June 2012 events, the OPW have asked CCC to progress a study of the catchment. 46

47 Carrigtwohill* Flood Risk Assessment Value (approx) 112k (for the study) Lead Organisation CCC acting as OPW agents. CCC procured the Engineering Consultants which is funded under the OPW Minor Works Programme. Consultant JBA Update Consultants appointed. Flood Risk Assessment ongoing. Reports to be finalised in Q Hydology and hydraulics reports have been sent to the OPW for comment week ending 22 nd March. Carrigtohill was investigated in the Lee CFRAMS, the outcome was that a further study was to be carried out by CCC. (*including Midleton Northern Relief Road Variation) 47

48 The Glen in Passage West Study and Remedial Works Value (approx) 100k (for study and works) Lead Organisation CCC acting as OPW agents. CCC procured the Engineering Consultants which is funded under the OPW Minor Works Programme. Consultant Byrne Looby Partners Update Engineering Consultants advancing works. Proceeding with Section 50 licence re-application to OPW. Part 8 Planning to follow approval of Section 50 (of the Arterial Drainage Act 1945). The solution entails a number of works. The cost of these works exceeds the initial OPW funding amount. A second application for funding under the Minor Works Scheme was applied for but turned down as the cost of the works does not meet the OPW cost benefit ratio of 1.5. CCC is proceeding to get the planning and section 50 licence. CCC has also asked the Consultant to look at phasing the works. 48

49 Riverstick and Environs Flood Relief Scheme Value (approx) 252k Lead Organisation CCC received funding from OPW under the Minor Works Programme. Consultant To be procured Update Consultants (to design bridge/culvert works and mitigation measures). Tenders received and tender assessment underway. 49

50 River Cleaning River Cleaning / Other works. Bandon river Inchigeelagh and Ballyvourney/Ballymakeera Rathbarry, Ballinscarty and Manch Bridge Bandon Flood Early Warning System Clonakilty Requests for Interim Works Douglas Interim Flood Defence Works 50

51 Bandon Flood Early Warning System Value (approx) 60k Lead Organisation CCC set-up & operate the system. Main source of funding was CCC. OPW gave 20k & use of their existing river gauges towards system Consultant RPS Update Operational since December Ongoing operational and staffing costs. Bandon FEWS will be reviewed following completion of the Bandon Flood Relief Scheme as the scheme is a defended solution. 51

52 Case Study Mallow Flood Relief Scheme 52

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56 The Phases North West South Mallow West Scheme Mallow South Scheme Mallow North Scheme

57 The Estimated Capital Values 12m 8.5m 6.5m Mallow West Scheme Mallow South Scheme Mallow North Scheme

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59 1:2 year flood 1:100 year flood

60 Principles of Scheme Protection against a 1 in 100 year flood. Flood warning system developed and implemented in parallel Mitigate any environmental impacts Schemes include demountable defences, defence walls and embankments, culverts, storm drains and pumping stations All structures designed to include for climate change Park Road protected against smaller flood events. 60

61 Benefits of Scheme The benefit of the Schemes are reductions in the following Damage to residential and commercial property Stress and Anxiety experienced by residents resulting from the threat of future flooding Economic loss to vulnerable traders Social Disruption to the local Community Disruption and Delays to traffic in the town. 61

62 Options Assessed Do Nothing Flood Proof Properties Flood Warning Upstream Catchment Storage Soft Engineering Measures and River Restoration Change Storage Profile in Flood Plains Improve Channel capacity through Maintenance Change the cross sectional area of the channel Allow more flow in the flood plain Improve hydraulics at local key constraints Direct Flood Defences

63 Options Selected for more Detailed Appraisal Defences, plus the following option to reduce river levels and thus defence heights Upstream Washlands Removal of island upstream of Mallow Bridge Realignment of the Mallow Bridge Approaches Downstream River Straightening Downstream Relief Channel

64 Mallow North Scheme Now Complete Protects properties north of the Blackwater Majority of Commercial properties north of the River Extent of Works from Dairygold factory on West End to Spa Glen out the Fermoy Road BAM appointed Main Contractor and commenced work in Spring month programme 1 month closure of Bridge Street Required 2 month closure of West End

65 Flood Defence Wall Open Channel Surcharge Culvert Flood Defence Embankment Mallow North Scheme

66 Mallow South Scheme Overview

67 Mallow West Scheme

68 Mallow Flood Relief Scheme Demountable Defences

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70 Council Carpark

71 Council Carpark

72 Council Carpark

73 Bridge Street

74 Bridge Street

75 Bridge Street

76 Thank You 76

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78 The overall preliminary cost estimate of the upgrade of 5km of the R624 (between the Dogs Lodge and the former IFI Plant) is 57.5 m. The proposed scheme has been split into 5 phases, with Phase 1 consisting of the construction of the proposed river crossing (300 lin.m) with associated tie-ins to the local road L2989 (Back Road to Cobh) involving an estimated cost of 29.7 million. If Phase 1 was delivered on the ground and linked in with the back road to Cobh, traffic heading to the former IFI plant would travel south over the new estuary crossing but would then have to travel north through Belvelly and along the substandard R624 alignment adjacent to the estuary. For this reason it would be strongly recommended that Phase 2 which entails the construction of a new road on Great Island linking the new crossing constructed in Phase 1 to the existing R624 at an estimated cost of 5 million be delivered in the one construction package with Phase 1 at a total estimated cost of 34.7 million. 78

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