Final Research Report
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Flood modeling and impact analysis using LiDAR data: A Case study for Ladyville Village, Belize. Final Research Report By: Alfred Cal Vancouver Island University August 31th, 2018 Abstract: Flooding is one of the most catastrophic natural disasters. Floods cause extensive damages on infrastructures and in some cases the loss of human life. Over the years flood frequency and severity has been increasing attributed to climate change. Coastal countries such as Belize have been impacted on a regular basis. A recent flood disaster in Ladyville, Belize, has shown a greater need for the monitoring of flood plain areas. In developed countries, flood mapping technologies and monitoring are at an advanced stage and can provide real-time early warnings. However, Belize is a developing country that is currently lacking reliable spatial data for disaster management. Considering this limitation, this research project contributes to the use of LiDAR as a technology that can be used for the extracting of relevant datasets for flood plain mapping. A PCA and image fusion technique of LiDAR with aerial photos was introduced to aid in the accurate extraction of structures. Ladyville village, Belize was chosen as a case study to evaluate the effectiveness of LiDAR technology in flood modeling and impact analysis. Ladyville was chosen as a study area because it is one of the most vulnerable communities in Belize that is prone to fluvial, pluvial and storm surge flooding. With the use of LiDAR derived datasets coupled with stream discharge data, 2D hydraulic modeling was completed in HEC- RAS to produce 2, 5, 10, 25, 50, and 100-year return period of flood depth, velocity, and extent. The boundary of the modeled flood plain was validated using photographs of past floods, anecdotal information from residents and NEMO personnel, and a comparison to past flood studies. A confusion matrix and a F measure statistic was used to determine the accuracy of the model with the locations of observed flood on the ground with the predicted flood model. The result of the F measure statistic shows an 80.6% reliability of the modeled flood plain. Based on the flood plain extents, impact analysis was conducted on the infrastructures and population of vulnerable areas. The results show that the most affected are residential infrastructures and 40% of the total population of study area can be impacted by a 100-year flood return period. In the absence of reliable spatial data, this study presented the effectiveness and advantage of using high resolution LiDAR data for flood modeling at an urban scale for Ladyville village, Belize. Keywords: Floods, 2D hydraulic model, LiDAR, DEM, DSM, nDSM, Land Cover, PCA, OBIA. i Table of Contents Abstract: ......................................................................................................................................... i List of Tables ................................................................................................................................ iv List of Figures ................................................................................................................................ v List of Symbols and Abbreviations ............................................................................................ ix Acknowledgements ....................................................................................................................... x Chapter 1: Introduction ............................................................................................................... 1 1.1 Background .............................................................................................................................. 1 1.2 Problem Statement ................................................................................................................... 3 1.3 Purpose and Research Question .............................................................................................. 4 1.4 Contribution to knowledge ...................................................................................................... 6 Chapter 2: Literature Review ...................................................................................................... 9 2.1 Importance of flood studies. ..................................................................................................... 9 2.2 Hydrology model ...................................................................................................................... 9 2.3 Importance of IDF and Peak Discharge for flood modelling. ................................................ 10 2.4 Importance of LiDAR data for flood modelling ..................................................................... 12 2.5 LiDAR Processing Software ................................................................................................... 14 2.6 LiDAR data filtering for flood modelling ............................................................................... 15 2.7 PCA and Image Fusion for feature extractions ....................................................................... 17 2.8 Floodplain modelling Software............................................................................................... 19 2.9 Floodplain model data inputs .................................................................................................. 21 2.10 Floodplain modelling Validation .......................................................................................... 22 2.11 Storm Surge Analysis ........................................................................................................... 23 2.12 Impact Analysis of floods ..................................................................................................... 24 2.13 Sensitivity Analysis .............................................................................................................. 26 Chapter 3: Methodology............................................................................................................. 28 3.1 Study Area Country Profile .................................................................................................... 28 3.2 Study Area .............................................................................................................................. 29 3.3.1 Data Collection .................................................................................................................... 31 3.3.2 Data Collection in a Developing Country ............................................................................ 35 ii 3.3.3 Field data collection ............................................................................................................. 38 3.4 Hydrological Analysis Component ......................................................................................... 41 3.5 LiDAR data processing component. ....................................................................................... 48 3.5.1 DEM (Digital Elevation Model) from LiDAR data ............................................................. 48 3.5.2 DSM (Digital Surface Model) from LiDAR data ................................................................ 50 3.5.3 Normalized Digital Surface Model (nDSM)........................................................................ 52 3.5.4 Intensity Image..................................................................................................................... 54 3.5.5 Building Foot Prints ............................................................................................................. 55 3.5.6 Building Extraction from LiDAR data only ........................................................................ 55 3.5.7 Pixel vs. object-based classification .................................................................................... 59 3.5.8 Object Based Building Extraction using PCA of LiDAR nDSM and Aerial Photos .......... 61 3.5.9 Land Cover from LiDAR data ............................................................................................. 78 3.5.10 OBIA Land Cover classification using image fusion of LiDAR Height and Intensity with Aerial photos. ................................................................................................................................ 82 3.6 Hydraulic component .............................................................................................................. 88 3.7 Flood plain validation component ........................................................................................ 103 3.8 Impact Analysis component .................................................................................................. 117 3.9 Storm Surge Analysis ........................................................................................................... 121 3.9.1 Storm Surge Validation...................................................................................................... 123 3.10 Sensitivity Analysis ............................................................................................................ 128 Chapter 4: Results and Discussion .......................................................................................... 131 4.1 Riverine Flood Results .......................................................................................................... 131 4.2 Storm Surge Results 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