Hydrodynamic Modelling for Flood Management in Bay of Fundy Dykelands By Michael Fedak A Thesis Submitted to Saint Mary’s University, Halifax, Nova Scotia in Partial Fulfillment of the Requirements for the Degree of Master of Science in Applied Science July 16, 2012, Halifax Nova Scotia © Michael Fedak, 2012 Approved: Dr. Danika van Proosdij Supervisor Department of Geography Approved: Dr. Ryan Mulligan External Examiner Department of Civil Engineering Queen’s University Approved: Dr. Timothy Webster Supervisory Committee Member COGS, NSCC Approved: Dr. Peter Secord Graduate Studies Representative Date: July 16, 2012 Abstract “Hydrodynamic Modelling for Flood Management in Bay of Fundy Dykelands” By Michael Fedak Storm surge in the coastal Bay of Fundy is a serious flood hazard. These lands are low-lying and adapted to farming through the use of coastal defences, namely dykes. Increasing rates of sea level rise due to climate change are expected to increase flood hazard in this area. In this thesis, flood risk to communities in the Avon River estuary of the Upper Bay of Fundy is investigated through computer based modelling and data management techniques. Flood variables from 14 possible storm surge scenarios (based on sea level rise predictions) were modelled using TUFLOW software. A GIS was used to create a database for simulation outputs and for the analysis of outputs. TUFLOW and a geographic information system (GIS) flood algorithm are compared .It was found that obstructions to flow controlled flooding and drainage and these features required the use of a hydrodynamic model to represent flows properly. July 16, 2012 2 Acknowledgements Funding Sources: • Atlantic Canada Adaptation Solutions Association part of the Natural Resources Canada Regional Adaptation Collaboratives (RAC) Project. • Environment Canada • Nova Scotia Department of Agriculture, Land Protection, Resource Stewardship • Nova Scotia Community College: Centre of Geographic Sciences (NSCC-COGS) • Saint Mary`s University Important Contributors: • My Parents; Janos and Beata • My Grandfather: Musci Sàndor • Phillip Ryan, Hydraulic Engineer: BMT-WBM Australia • Kevin McGuigan and Nathan Crowell: Applied Geomatics Research Group • Ken Caroll & Darrell Hingley: NS Dept of Agriculture • Emma Poirier, Jennie Graham, Barbara Perrot-Pietersma, Casey O`Laughlin, Ben Lemieux, Greg Baker, In_CoaST Research Unit, and MP_SpARC: Saint Mary’s University • Drs. Paul Muir and Tim Webster: Supervisory Committee • Dr. Danika van Proosdij: Main Supervisor • Dr. Ryan Mulligan: External Examiner 3 Table of Contents Abstract ............................................................................................................................... 2 Acknowledgements ............................................................................................................. 3 Figures ................................................................................................................................. 7 Tables .................................................................................................................................. 8 Equations ............................................................................................................................. 9 List of Symbols ................................................................................................................... 9 CHAPTER 1: Introduction and Literature Review ........................................................ 10 1.1 Thesis Statement ..................................................................................................... 11 1.2 Rationale ................................................................................................................. 12 1.3 Purpose and Objectives ........................................................................................... 13 1.4 Interdisciplinary Approaches in Flood Modelling .................................................. 13 1.5 Data Requirements .................................................................................................. 14 1.5.1 Terrain Data and Bathymetry ........................................................................... 14 1.5.2 Boundary Conditions ....................................................................................... 16 1.5.3 Surface Roughness ........................................................................................... 17 1.6 GIS Based and Numerical Modelling Methods ...................................................... 19 1.6.1 GIS based methods .......................................................................................... 19 1.6.2 Numerical Methods .......................................................................................... 22 1.7 Model Evaluation .................................................................................................... 31 1.7.1 Model Calibration and Sensitivity Analysis .................................................... 32 1.7.2 Model Validation ............................................................................................. 34 1.7.3 Model Errors and Uncertainty.......................................................................... 34 1.8 Definitions of Risk, Hazard and Vulnerability. ...................................................... 37 1.9 Hazard and Vulnerability Determining Factors ...................................................... 38 1.10 Data Management and Decision Support.............................................................. 40 CHAPTER 2: Study Area and Background ...................................................................... 43 2.1 Geomorphological Characteristics and Tidal Dynamics ........................................ 46 2.2 History of Flood Management in the Dykelands .................................................... 48 CHAPTER 3: Methods ..................................................................................................... 51 3.1 Flood Modelling Process ........................................................................................ 52 3.2 Relevant Environmental Processes and Characteristics.......................................... 52 4 3.2.1 Bathymetry and Coastal Topography .............................................................. 52 3.2.2 Implications of Geomorphology for Model Selection ..................................... 55 3.2.3 Tides and Currents ........................................................................................... 56 3.2.4 Sea Level Rise and Tidal Changes ................................................................... 57 3.3 Hydrodynamic Modelling Methods ........................................................................ 58 3.3.1 Hydrodynamic Model ...................................................................................... 59 3.3.2 Requirements for Decision Making and Data Collection ................................ 61 3.3.3 Validation ......................................................................................................... 65 3.3.4 Final Model Configuration and Simulation Set-Up ......................................... 81 3.3.5 Assumptions and Limitations .......................................................................... 90 3.4 Data Management ................................................................................................... 91 CHAPTER 4: Results ....................................................................................................... 94 4.1 Speed and Extent of Flooding ................................................................................. 95 4.1.1. Flood Extent .................................................................................................... 95 4.1.2 Speed of Flood Onset and Drainage .............................................................. 102 4.2 Depths/Water Levels ............................................................................................. 106 4.3 Velocities .............................................................................................................. 112 4.4 Velocity Depth Product Hazard. ........................................................................... 114 4.5 Special Cases: ........................................................................................................... 116 4.5.1 Dyke Breach ................................................................................................... 117 4.5.2 Partial Blockage ............................................................................................. 121 CHAPTER 5: Discussion ................................................................................................ 125 5.1 Natural and Man-made Flood Controls ................................................................ 125 5.2 Comparison of Raster DEM Flood Simulation and Hydrodynamic Modelling. .. 127 5.3 Sources of Uncertainty and Error.......................................................................... 134 5.3.1 Source Uncertainties ...................................................................................... 135 5.3.2 Pathway Uncertainties.................................................................................... 137 5.3.3 Receptor Uncertainties ................................................................................... 139 5.3.4 Errors .............................................................................................................