Engineers Ireland Presentation

Transcription

1 Engineers Ireland Presentation Kevin Gallagher Chartered Engineer Senior Executive Engineer Cork City Council Local Authority Response to Flooding in an Urban Area

2 INTRODUCTION: Context Flooding Types & Flood Risk Flood Response Urban Planning & Lee CFRAMS Lower Lee Flood Relief Scheme Local Authority Response to Flooding in an Urban Area

3 Context: Flood Prone Characteristics Low Lying City Centre Head of a large Harbour Mouth of flashy river Tributaries Topography Local Authority Response to Flooding in an Urban Area

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7 FLOODING TYPES & FLOOD RISK: Tidal Fluvial Pluvial Infrastructural

8 TIDAL: Most frequent type Influence Factors Astronomical Tides Atmospheric Pressure Wind especially Direction Storm Surge Varying degrees of Impact

9 TIDAL: Level & Duration Type of Tide Height/Range* Normal High Tide 1.3m 1.8m Normal Spring Tide 2.0m High Spring Tide 2.2m Flood Level Commencement 2.4m Extensive Flood Level 2.8m 3.0m * Malin Head Datum

10 TIDAL FLOODING JANUARY 2014 Date Time Tide (m OD) Predicted Surge (m) Total Water Level (m OD) 2/1/ : : /1/ : : /1/ : : /1/ : : /1/ : :

11 TIDAL FLOODING FEBRUARY 2014 Date Time Tide (m OD) Predicted Surge (m) Total Water Level (m OD) 31/1/ : : /2/ : : /2/ : n/a n/a 19: n/a n/a 3/2/ : : /2/ : :

12 Weather Report Cork Airport 4/2/14

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15 Fluvial: - Channel capacity Major events - infrequent Medium - western end of City Local - Glasheen Clashduv, Magazine Road - Blackpool - Ballyvolane

16 River Lee Flood 19 th /20 th November 2009 Inniscarra Dam Alert Levels Discharge Rate at Dam m3/sec Flood Type No Flood Minor > 250 Serious

17 River Lee Flood 19 th November am Inniscarra Dam advises City Council discharge would be 150 cumecs rising to 250 to 300 cumecs over next few hours 12 Noon City Council warns businesses at Carrigrohane Road of possible flooding Flood Warning Issued by City Council Dam advises discharge will be > 300 cumecs

18 River Lee Flood 19 th November :40 High Tide passes without incident Dam advises discharge to go to 450 cumecs Carrigrohane Road under heavy flood. Army and Civil Defence Alerted Midnight Lee Road Waterworks Shutdown due to flooding

19 River Lee Flood 20 th November am Drinking Water Incident Plan (DWIRP) Initiated 4.00am Quay wall collapses at Grenville Place 4am 6.30am City Council and Emergency Services on the streets. 7am Emergency water supplies by tankers start 29 th November Piped water supplies restored to most households.

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21 Blackpool Flood 28 th June th June Countrywide severe weather warning received. Rainfall up to 70mm possible Inniscarra Dam situation checked (Standard Practice since 2009). Discharge Rates normal. No risk of tidal flooding. Expected result was ponding on streets. Traffic Section put on alert for possible road closures

22 Blackpool Flood 28 th June th June Midnight to 3am In excess of 30mm rain fell with 18.3mm between 1am to 2am (Status Red Severe Weather Warning is >40mm in 6 hours) 2.30am Flooding reported from Blackpool 4am 6.30am Volume of water in River Bride exceeds culvert capacity causing flow onto Blackpool streets. Depths up to 1.2m River Bride burst its banks upstream at Commons Inn and floods N am Flooding abated Flooding in Ballyvolane due to water unable to enter culvert system

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25 Pluvial: - Infrastucture capacity Intense Rainfall Events Steep Gradients Sun Valley Drive/Watercourse Road Penrose Quay

26 Infrastructural Watermains Sewers Fever Hospital Steps Shandon St.

27 Flood Response: Absence of Defence Need for Forecast Alert System Text, Media Emergency Response Inter Agency Flood Plan

28 Cork City Inter Agency Flood Plan Warning Level Discharge Rate at Dam m3/sec Tidal Height m AOD Flood Type LA Response Alert Level No Flood Normal Ops Alert Level Minor Routine Preps Record Flood Alert Level 3 > 250 > 2.7 Serious Flood Emergency Response Plan Alert Level 4 Flood Assessment Team Major Major Emergency Plan

29 Cork City Inter Agency Flood Plan Met Eireann Weather Warning Rainfall Green No Significant Hazard Yellow - Weather Alert Orange Weather Warning Red Severe Weather Warning < 30mm in 24 hours < 25mm in 12 hours < 20mm in 6 hours 30mm 50mm in 24 hours. 25mm 40mm in 12 hours. 20mm 30mm in 6 hours 50mm 70mm in 24 hours 40mm 50mm in 12 hours 30mm 40mm in 6 hours >70mm in 24 hours > 50mm in 12 hours > 40mm in 6 hours

30 Cork City Inter Agency Flood Plan Met Eireann Severe Weather Warning Rainfall Review Equipment and Man Power in Drainage Dept. Liaise with Road Maintenance re: Gully Clearance. Alert Staff Officer for requests for assistance from public & transfer to outdoor staff. Liaise with Traffic Section re: Road Closures Inspect & clean, where necessary, River Screens Respond to Localised Flooding Complaints Post-Flood Check the Sewer System for Damage and Repair Assist other City Council Sections with Post-Flood Works

31 The Planning System and Flood Risk Management Guidelines for Planning Authorities Published by DEHLG and OPW November 2009

32 Planning Guidelines & Flood Zones 3 Types of Flood Zone Flood Zone A Flooding Probability > 1 in 100 Fluvial, > 1 in 200 Tidal. Flood Zone B Probability between 1 in 100 to 1 in 1,000 Fluvial, 1 in 200 to 1 in 1,000 Tidal Flood Zone C Probability < 1 in 1,000 for Fluvial and Tidal

33 Planning Guidelines & Flood Zones Development Type Vulnerability Classes Highly Vulnerable Hospitals, Schools, Residential, Flood Command Centres Less Vulnerable Retail, Leisure, Commercial, Industrial, Non-Residential Water Compatible Docks, Marinas, Wharves, Amenity Open Space & Outdoor Sports

34 Planning Guidelines & Flood Zones Appropriate Development in Flood Zones Highly Vulnerable Flood Zone C Less Vulnerable Flood Zones B & C Water Compatible Flood Zones A, B & C

35 Planning Guidelines & Flood Zones Development Management Justification Test for Inappropriate Development in Flood Zones Subject Lands Zoned for Proposed Use Flood Risk Assessment

36 Flood Risk Assessment Will not increase flood risk &, if possible, reduce overall risk Minimise risk to people, property, economy and environment Residual risks managed to acceptable level Compatible with wider planning objectives

37 Lee CFRAMS Flood Maps Extent Maps Depth Maps Velocity Maps Hazard Maps Current Extent Maps Mid-Range Future Scenario Extent Maps

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42 Lower Lee Flood Relief Scheme Detailed Information about this scheme is available at