Comhairle Chontae Fhine Gall Comhairle Chontae na Mhí FINGAL COUNTY COUNCIL MEATH COUNTY COUNCIL RIVER TOLKA FLOODING STUDY TECHNICAL REPORT VOLUME 2: RIVER MODELLING REPORT October 2003 River Tolka Flooding Study Technical Report No. 2 River Modelling Report TABLE OF CONTENTS 1 INTRODUCTION.............................................................................................................................. 1 1.1 APPOINTMENT OF MCOS ............................................................................................................ 1 1.2 PROJECT APPRECIATION ............................................................................................................. 1 1.2.1 Background/Flooding History............................................................................................. 1 1.2.2 Study Context .................................................................................................................... 3 1.3 OBJECTIVES OF THE REPORT....................................................................................................... 3 2 CATCHMENT DESCRIPTION......................................................................................................... 5 2.1 OVERVIEW................................................................................................................................... 5 2.2 RIVER NETWORK......................................................................................................................... 5 2.3 INTERACTION WITH OTHER STUDIES .............................................................................................. 5 3 DATA COLLECTION....................................................................................................................... 6 3.1 REPORTS.................................................................................................................................... 6 3.2 RAINFALL DATA........................................................................................................................... 6 3.3 FLOODS RECORDS/LEVELS.......................................................................................................... 6 3.4 FLOW INFORMATION .................................................................................................................... 7 3.5 PROPOSED RIVER GAUGES........................................................................................................... 8 3.6 TOPOGRAPHICAL DATA / ORTHO-PHOTOGRAPHY .......................................................................... 9 3.6.1 Orthophotography.............................................................................................................. 9 3.6.2 Topographical Survey........................................................................................................ 9 3.7 PIPE NETWORKS ......................................................................................................................... 9 3.7.1 Drainage Networks .......................................................................................................... 10 3.8 FLOOD PROTECTION WORKS / RIVER ALTERATIONS ..................................................................... 11 3.8.1 Historical Works............................................................................................................... 11 3.8.2 Recent / Proposed Works................................................................................................ 11 3.8.3 Study Interim Works ........................................................................................................ 11 3.9 TIDAL INFORMATION .................................................................................................................. 11 4 LAND USE AND PLANNING ........................................................................................................ 12 4.1 EXISTING LAND USE .................................................................................................................. 12 4.2 CONSTRAINTS MAPPING ............................................................................................................ 12 4.2.1 Sites & Monuments; Special Areas of Conservation; Special Protection Areas and Natural Heritage Areas:.................................................................................................................. 12 4.2.2 Catchment Landuse / Corine Data: ................................................................................. 12 4.2.3 GSI Bedrock / Groundwater and Aquifers: ...................................................................... 12 4.3 FUTURE DEVELOPMENT WITHIN THE CATCHMENT ........................................................................ 12 5 HISTORICAL EVENT ANALYSIS ................................................................................................. 14 TH TH 5.1 ANALYSIS OF FLOOD EVENT OF 14 – 15 NOVEMBER 2002...................................................... 14 5.1.1 Rainfall Records............................................................................................................... 14 5.1.2 Affected areas..................................................................................................................14 5.1.3 Impact on River Tolka Flood Study ................................................................................. 18 5.2 ANALYSIS OF FLOOD EVENT OF 1954 ......................................................................................... 19 5.2.1 Rainfall Records............................................................................................................... 19 5.2.2 Affected areas..................................................................................................................19 5.3 ANALYSIS OF FLOOD EVENT OF NOVEMBER 2000 ....................................................................... 19 5.3.1 Rainfall Records............................................................................................................... 19 5.3.2 Affected areas..................................................................................................................19 5.4 FLOOD FREQUENCY ANALYSIS .................................................................................................... 19 5.4.1 Introduction ...................................................................................................................... 19 5.4.2 Hydrological data series .................................................................................................. 20 5.4.3 Fitted Distribution based on Peak Over Threshold Series .............................................. 20 074515001Rp0032ADE.doc i Rev F01 River Tolka Flooding Study Technical Report No. 2 River Modelling Report 5.4.4 Annual Maxima Series..................................................................................................... 21 5.4.5 Expansion of Annual Maxima Series............................................................................... 21 5.4.6 Catchment Characteristics Analysis ................................................................................ 21 5.4.7 Summary.......................................................................................................................... 23 5.5 SEA LEVEL / FLOOD INTERACTION .............................................................................................. 24 5.5.1 Tidal Frequency Analysis................................................................................................. 24 5.5.2 Sea levels ........................................................................................................................ 26 6 LONG TERM CLIMATE CHANGE IMPACTS............................................................................... 28 6.1 INTRODUCTION .......................................................................................................................... 28 6.2 GDSDS PREDICTIONS FOR CLIMATE CHANGE................................................................................ 29 6.3 APPLICATION OF CLIMATE CHANGE TO THE RIVER TOLKA .............................................................. 30 6.4 JOINT PROBABILITY OF TIDAL AND FLUVIAL FLOODING................................................................... 31 6.5 SUMMARY.................................................................................................................................. 31 7 MODEL CONSTRUCTION ............................................................................................................ 32 7.1 OVERVIEW ................................................................................................................................32 7.2 MODEL DEVELOPMENT .............................................................................................................. 32 7.2.1 Modelling Software .......................................................................................................... 32 7.2.2 Phased Model Development............................................................................................ 32 7.2.3 User Defined Flags .......................................................................................................... 33 7.3 HYDROLOGICAL MODEL ............................................................................................................. 33 7.3.1 Rainfall/Runoff Model 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