Flood Risk Analysis Depth Dependent Cost Estimation for Urban Areas Alvaro Fonseca and Mia Holmbo Lind, Grontmij Denmark Copyright 2015 Grontmij A/S CVR 48233511
Grontmij: Engineering Consultancy 1 Business Lines Planning & Design Transportation & Mobility Water & Energy 9 main markets 100 offices world wide 3 business lines 6,000 employees 70,000 projects a year
Agenda 1. Background 2. Grontmij Flood Risk Concept 3. Methods 4. Results and Discussion 5. Perspectives 6. Questions? Copyright 2015 Grontmij A/S CVR 48233511
Background Copyright 2015 Grontmij A/S CVR 48233511
Background National Context Denmark 4 Climate Change Adaptation Plans All municipalities ought to map risk Standard risk maps based on building values not sufficient New FREE Danish Geodata From 1 st January 2013 almost all geodata available online Could the new free geodata be used in mapping risk? Joined Development Project Grontmij A/S, Ishøj Municipality and Ishøj Utility Company Photo: Mathias Øgendal
Background Ishøj adapting to Climate Change (2013) 5 Problem Coastal municipality (Baltic Sea) Vulnerable to storm surges and sea level rise Urban flooding In 2007, 2009, 2011 and 2014 Combined/Separate sewage system Important assets Harbour with Modern Art Museum Historic village Protected buildings Bronze age relics Burial mounts
Grontmij Flood Risk Concept Copyright 2015 Grontmij A/S CVR 48233511
Concept Framework for Flood Risk Assessment 7 Flood Risk Flood Risk Hazard Mapping Hazards Vulnerability Hydro-dynamic modelling Flooding Probability Extent and Depth GIS-based Risk Model Physical impact Expected Annual Damage (EAD) Intangible cost Vulnerability Which areas are flooded? What s the impact? GIS-based Risk model Risk maps Cost-benefit perspectives Adapted from Zhou (2012) Zhou, Q. 2012. Urban drainage design and climate change adaptation decision making. PhD Thesis DTU Environment Department of Environmental Engineering, Technical University of Denmark.
Concept Conceptual GIS Model 8 Hazards Rainwater and seawater Extend, depth and frequency Vulnerable assets and cost estimation Buildings and other landscape features Hotspots Representative Areas Sewage catchments EAD summarized Prioritizing initiatives Hazard maps GIS-based Risk Model Expected Annual Damage (EAD) Vulnerable Monetized Assets
Methods Copyright 2015 Grontmij A/S CVR 48233511
Methods Hazard mapping 10 Urban Drainage Model 3-D model results (MIKE Flood) Sea level rise model Provided as free geodata Based on a detailed DTM Information from flood maps Depth Extent Frequency Return Periods (T, years) T = 5, 10, 20, 50 and 100 Photo: Mathias Øgendal
Methods Vulnerable Landscape Features and Assets 11 Selected features Roads Parks and natural areas Churches and graveyards Technical facilities Historical relics Buildings Cadastre Records (not free) lookup for basements Hotspots Hospitals, data centres, protected buildings etc.
Methods Cost Estimation 12 Buildings Value estimated from public property valuation Damage costs in % of total value based on flood depth, e.g. 40 cm water = 10% of value Other layers Estimated damage cost per m 2 Hotspots Appointed by Ishøj municipality and utility company Cost estimation based on latest insurance cost after flooding events Provided by the umbrella organization for the insurance companies Depths Buildings w/ basement Buildings w/o basement Buildings - no evaluation record Industrial buildings Roads, park and sports facilities (cleanup) Rails, techfacilities*, relics* and graveyards* Nature (stewardship) cm % of value % of value DKK pr. m 3 DKK pr. m 3 DKK pr. m 3 DKK pr. m 3 DKK pr. m 3 0,3-30 0 2 0 0 0 60 0,02 30-50 10 10 600 1000 10 80 0,04 50-100 30 30 700 1200 30 80 0,06 100-150 40 40 800 1400 40 100 0,08 >150 50 50 1000 1500 40 100 0,1
Methods EAD and Risk Assessment 13 Consolidation E.g. sewage catchments areas Privacy of each house owner protected Expected Annual Damage (EAD) Finding max total cost for each T-event Probability Hazards Extent and Depth Flood Risk Physical impact Vulnerability Intangible cost Risk Assessment Each catchment A resulting map showing which areas where adaptation measures will be initiated GIS-based Risk Model Expected Annual Damage (EAD)
Methods GIS Application 14 Threshold Overlay analysis in Model Builder Raster to vector All flood maps to polygons Layers based on max. depth Threshold height = 30 cm Tools Select by location, Intersect, Merge, etc. Summarizing Iterations over events and depths Five events for rain and sea level: 5, 10, 20, 50 and 100 yr Five Depth Intervals
Results and Discussion Copyright 2015 Grontmij A/S CVR 48233511
Results and Discussion Expected Annual Damage 16 Return Period vs EAD Depending on extent and cost Consolidated on areas Validation: plan 2011 and 2013 Solid base for Action Plan EAD for T = 20 yr Area EAD T5 EAD T10 EAD T20 EAD T50 EAD T100 MAX EAD Prio 2011 Prio 2013 Name F1 kr. 79.644.894 kr. 41.842.038 kr. 20.921.019 kr. 8.270.776 kr. 4.167.257 kr. 79.644.894 1 1 Strandområdet J1 kr. 320.052 kr. 825.133 kr. 412.567 kr. 158.605 kr. 84.419 kr. 825.133 2 17 Ishøj Landsby P1 kr. 5.108.820 kr. 4.368.834 kr. 2.184.417 kr. 927.350 kr. 599.307 kr. 5.108.820 3 9 Tranegilde P2 kr. 3.392.324 kr. 2.378.437 kr. 1.189.218 kr. 607.337 kr. 392.917 kr. 3.392.324 4 11 Kolonihaver
Results and Discussion Consolidated and prioritized areas 17 Match between Priority Areas (catchments) and Climate Change Adaptation Investments
Perspectives Copyright 2015 Grontmij A/S CVR 48233511
Perspectives Recommendation and further application 19 Lessons learned Better pre-processing methods Retrieving and preparing geodata Fully automated procedure not achieved Static workflows (small pieces) Model builder not always stable Python cleaning might help? Validation Insurance data from specific historical event Does the used cost estimation add up? Can we update the methods? Application used for other hazards Rising Groundwater (very relevant in DK) Storms
Thank you Questions? CONTACT Alvaro Fonseca Project Manager P +45 4348 4618 E AVF@grontmij.dk www.grontmij.dk CONTACT Mia Holmbo Lind Physical Geographer P +45 43486932 E MIA@grontmij.dk