#1- Bangladesh Climate Change Resilience Fund (BCCRF) And The Development Economics Research Group Present Urban Flooding of Greater Dhaka in a Changing Climate Building Local Resilience to Disaster Risk Susmita Dasgupta, Asif Zaman, Subhendu Roy, Mainul Huq, Sawar Jahan and Ainun Nishat Presenter: Dr. Susmita Dasgupta Lead Environmental Economist, DECEE 2016 Megacity Dhaka Location: Lower reaches of the Ganges Brahmaputra Delta Greater Dhaka Area: 1,548 sq. km Elevation: 0 10m MSL Average Rainfall: 2,000 mm per year Monsoon: June - September Population: 14 million (BBS 2012) Dinajpur Rajshah NT1 Deripara Tongi NIDS Dhaka Gabtoli ঢাকা Alipurduar Keranigang MEGHALAYA oshillong H Bangladesh apur Dhaka ঢাকা Jessore E Khulna Chowmuha ENGAL Satkhira Kolkata Population Density: 34,000 per sq. km Rajpur Sonarpur Sundarban angath Digha Dhaka will become the world's fifth largest city by 2025 (UN 2010) RIPUB Chittagong Chandanaish Cox's Baza ONSORTAL Sittwel 08/12/2016 1#2Urban Flooding: A Recurring Problem in Dhaka कान বস্তু ও পটি মুক্তপালয় বাংলাদেশ তাঁত বোর্ড 54+ Flooding batters the city, affecting communications, livelihoods and service facilities every monsoon. The fringe areas, slums and shanties suffer more. ■Recent Devastating Floods: 1974, 1987, 1988, 1998, 2004, 2007, 2009. Dhaka Urban Flooding: Three Potential Threats Natural Factors: Flat topography and low relief of the area ■ Developmental Factors: unplanned and unregulated urbanization, low capacity drainage and sewerage infrastructure that have not kept pace with the growth of the city or demand for services, siltation in available channels, obstructions, mainly through uncontrolled construction in the natural flow of the storm water, reclamation of and construction in natural drainage areas (marshlands), etc. Climate Change Aspects: More erratic rainfall and increase in the frequency and intensity of extreme rainfall events. 08/12/2016 2#3Research Motivation Gradual filling up of flood plains, rivers, canals and other water bodies with rapid urbanization will aggravate the water logging over time. More erratic rainfall and increase in the frequency and intensity of extreme rainfall events with climate change may further worsen Dhaka's flood vulnerability in the future. ■This study will provide local decision-makers an effective planning approach to minimize the damage from urban flooding. Presentation Topics Geographic coverage Study components and collaborators - Future scenarios Hydrological Modeling Illustrative Example: Central Dhaka Flood vulnerability at ward level Current climate adaptation deficit Climate change effects Cost-Benefit comparison Message to policy makers Complementary flood mitigation measures Potential use of the study 08/12/2016 3#4- Old Dhaka Central Dhaka Kallyanpur Goranchatbari Detailed Study Area N IWM Tongi Khal Uttara Goranchatbari Airport Savar Pallabi Gazipur Badda Eastern Dhaka Mirpur Kafrul Gulshan Eastern Dhaka DND (Dhaka-Narayanganj-Demra) Narayanganj Kallyanpur Mohammadpur Tejgaon Central Dhaka Khilgaon Dhanmondi Ramna Motijheel Sabujhagh Lalbagh Kamrangir Char Kotwali Old Dhaka Sutrapur Shyampur Keraniganj Study Components Buriganga Legend Kaliganj DRAINAGE MODELS Central Dhaka Goranchatban Narayanganj Kalyanpur Old Dhaka Eastern Dhaka OND Rivers khya Demra Sonargaon DND DND Narayanganj Narayanganj Kadam Rasul Dhaleswari Bandar Assessment of Disaster Resilience: Local preparedness for urban flooding emergencies of constituent wards was analyzed. Hydrological modeling: Location-specific depth and duration of flooding from an intense rainfall event was estimated. Flood vulnerability: The 10 most vulnerable wards of Greater Dhaka Area taking into account their exposure to flood as well as socioeconomic vulnerability and disaster resilience were identified. Design of adaptation: Recommended adaptation measures for each study area were developed and itemized adaptation costs were estimated. Estimation of expected damage: Expected economic damage from an intense rainfall event in 2050 and cumulative damage from similar rainfall between 2014 and 2050 with and without adaptation were estimated. Complimentary flood mitigation measures were recommended. 08/12/2016 4#5Study Components & Collaborators Assessment of Disaster Resilience: BUET. Hydrological modeling: IWM. Flood vulnerability: international consultants and BUET. Design of adaptation: DPG and IWM in consultation with local experts. Estimation of expected damage: international consultants in consultation with DPG and IWM. Estimation of Adaptation Cost : DPG and IWM in consultation with local experts. Complementary Flood Mitigation Measures: DPG in consultation with local experts. Future Scenarios Baseline Rainfall (without climate change scenario): Historic September 2004 rainfall event (341 mm rainfall in 24 hours) Climate Change Rainfall Scenario: A 16 percent increase in 24-hour rainfall in Dhaka in 2050 as compared to the baseline. All planned and proposed drainage improvements discussed in the RAJUK's DAP, Sewerage Master Plan of DWASA, Narayanganj City Corporation's Concept Vision Plan, recommendations of JPZ et al., IWFM, IWM will be implemented. 08/12/2016 15#6Hydrological Modeling: Three Steps A Dhaka is surrounded by 6 rivers and canals 1. Basin-Level Modeling: Model developed by IWM for the GBM basin was used to estimate future flow changes of Brahmaputra (Jamuna) River due to climate change. 2. Region-Level Modeling: NCRHD was used to simulate monsoon seasonal flows and water levels of the river network in the extended study area. 3. Detailed Urban Area Modeling: MIKE11 and MIKE Urban were used for detailed level of hydrological and hydrodynamic modeling of the urban drainage system and relevant catchments. Surrounding Dhak D Hydrological Modeling: Conceptual Framework Step 1 Basin-level hydrological modeling Other input data Flows of major rivers Other input data Step 2 Regional hydrological and hydrodynamic modeling DEM of DMDP area Indicative flood maps of extended study area Flows and water levels of regional rivers Step 3 Detailed hydrological and hydrodynamic modeling Other input data Data set Model elements DEM of Dhaka area Flood maps of detailed study area Data set 08/12/2016 0#7Hydrological Modeling: Detailed Area Modeling Drainage infrastructure scenarios: • Planned improvements • Additional . investments Adaptation to climate change Rainfall changes A1F1 and B1 Expected land cover changes Rainfall-runoff modeling Sea-level rise estimates 1-D hydrodynamic modeling Subsidence estimates DEM Map showing waterlogging depths and duration for each scenario and at different probabilities of occurrence Detailed Area Modeling: Data Data Topography (DEM) Meteorological information Drainage infrastructure Land cover River stage River flow River sections, slopes and alignments Population density Source IWM, Survey of Bangladesh BMD and BWDB Dhaka-WASA BUET and RAJUK BWDB BWDB IWM BBS 08/12/2016 7#8Central Dhaka - Land Elevation Central Dhaka 2004 DEM Legend Central Dhaka 2050 DEM DEMnPWD).. 34 Central Dhaka - Land Use Landuse (2004) for Central Dhaka (DAP) 08/12/2016 Proposed Landuse for Central Dhaka (DAP) 8#9Central Dhaka - Drainage Legend Cat Lates Central Dhaka Drainage Network and Catchments A Predon Bangladesh Transverse Mercat WM Central Dhaka - Flood Map without Climate Change MEE wa WHE WAY WAY Kaarniga Legend WAS was Kamangir Char a. Pl (341 mm/24 hour) WAZ WA Flood depth 100 WIT Flead depth map with 3424 evest in 2050 without climate change and planned drainage improvement 08/12/2016 9#10Central Dhaka - Adaptation Deficit 1. At Gulshan, Banani and Hatir Jheel Lakes - Reduce initial water levels from 5 m PWD to 4 m PWD 2. At outfall of Panthapath Box-Culvert- Install a new pump station with 12.5 m /s capacity and 80 % efficiency. 3. Near Bashabo Water Pump station of DWASA- Install new pump station and sluice gate; pump capacity is 15 m/s, with 80% efficieny, and gate size is 4 m x 3 m. Extreme rainfall in 2050 Flood free 0.1m-0.25 m 0.25m-0.75m 0.75m-1.5m > 1.5m Average Duration above 0.1m (hours) Maximum flooded area (sq. km) 341mm/24 hour Future without Adaptation deficit 26.4 8.8 1.9 0.3 1.8 10 36.4 0.7 0.3 0.1 1.7 1 Central Dhaka - - Flood Maps with & without Adaptation Deficit Moha Legend A a. Pl (341 mm/24 hour) W4 Wa Was WAS Kameangir Char was WAY Was b. Pl+Al (341 mm/24 hour) Wa Dhanmo Kamrangir Char Flead depth map with 341mm in 24 Legend Flood depth event in 2050 without climate change neve Nast Flood depth ( Fload depth map with 341 in 2015 event in 2050 CC) and additional Now PSgeded in desno 08/12/2016 10#11Central Dhaka - Additional Adaptation for Climate Change 1. 2. Near Russel Square- Installation of a new sluice gate (3.4m x 3.4m) with automatic operation to divert excess water to Dhanmondi lake at the time of peak runoff and prevent backwater flow from Panthapath Box-Culvert. Near Russel Square- Reactivate the existing sluice gate (2m x 2m) and automatic operation with the new gate to divert excess water to Dhanmondi lake at the time of peak runoff. Central Dhaka - Extent and Duration of Flood with and without Climate Change Average Extreme rainfall in 2050 Flood free 0.1m- 0.25 m 0.25m- 0.75m 0.75m- 1.5m Duration > 1.5m above 0.1m (hours) 341 mm/ 24 hour 26.4 8.8 1.9 0.3 1.8 10 396 mm/ 24 hour 25.1 10.1 1.9 0.3 1.8 12 341 mm/24 hour without 36.4 0.7 0.3 0.1 1.7 1 Adaptation deficit 396 mm/ 24 hour but without 35.7 1.1 111 0.5 0.2 1.8 2 Adaptation deficit 396 mm/ 24 hour without 36.1 0.9 0.4 0.1 1.8 1 Adaptation deficit and with adaptation for climate change 08/12/2016 11#12Central Dhaka-Adaptation Cost Addressing Current Climate Deficit: Pump station, Bashabo * Pump station, Panthapath Total Tk. Million 849.5 600.00 1,449.5 Addressing Climate Change Deficit: Total estimated cost, sluice gates at Russel Square 91.1 Total Combined Cost 1,540.6 Calculation based on price of pump, related mechanical, electrical and civil works, land acquisition and sluice gate. Central Dhaka - Cumulative Damage from Extreme Rainfall Events during 2014-2050 Cumulative damage between 2014 and 2050 from an intense rainfall event based on random assignment of 1% probability of occurrence during each year: If there is no climate change and no action is undertaken: Tk. 56,315 million If current climate adaptation deficit is met: Tk. 11,460 million If there is climate change (no change in frequency-only more intense rainfall) and no action is undertaken: Tk. 65,754 million If current climate adaptation deficit is met and climate change adaptation is undertaken: Tk. 12,367 million Cumulative damage between 2014 and 2050 from an intense rainfall event based on random assignment of 5% probability of occurrence during each year: If rainfall intensity remains the same and no action is undertaken: Tk. 65,322 million If current climate adaptation deficit is met: Tk. 13,119 million If there is climate change and no action is undertaken: Tk. 76,205 million If current climate adaptation deficit is met and climate change adaptation is undertaken: Tk. 14,159 million 08/12/2016 12#13Damage Assessment Water Levels & Expected Impact: (0 - 0.1 m): (0.1 m 0.25 m): (0.25 - 0.75 m) (0.75 -1.50 m) (> 1.50 m) No impact slight impact low impact moderate impact extensive impact It has been found that a depth level below 0.25 m produces little damage in most affected areas as people in Dhaka have learned to adapt to such level of flooding as a common occurrence every year. Duration of Flooding & Expected Impact: duration of flooding above 0.25 m level is analyzed up to 10 days in order to examine the severity of flood damage as it was found that water starts receding rapidly from most areas in Dhaka city by that period. Damage Assessment: Methodology ■ The damage is estimated separately for the following main sectors of the economy: residential, commerce and industry, health, roads, railways and other surface transport. ■ In each sector, efforts have been made to estimate the damage to physical capital and the damage to earnings to get an estimate of total damage. > Damage to Physical Capital = Value of Physical Capital* Percentage of Physical capital Exposed to Flooding *Damage Factor Damage factor is estimated based on the depth and duration of flooding. > Damage to Earning = Daily Value of Income/Output * Average Number of Days of Loss. 08/12/2016 13#14Residential Damage & Income Loss Residential Damage Building Repair Cost Building Clean-up Cost Property Damage Residential Building Repair Cost Dhaka's categorization of building structures: Jhupri, kutcha, semi-pucca and pucca were considered. Pucca structures were further divided into economically weaker section (EWS), middle-income groups (MIG) and high-income groups (HIG). Building upgrades would reduce the number of jhupris and kutcha structures and a percentage of semi-pucca buildings will be transformed to pucca over time. Jhupri, Kutcha, semi-pucca structures are one-storied buildings, average pucca structure consists of two (EWS), three (MIG) or four (HIG) stories. Flood damage will be restricted only to the first floor. Building construction costs of different types of buildings were estimated from the ACC Help Home Building Calculator. Repair costs of Jhupri, kutcha, semi-pucca and pucca are 50%, 25%, 12% and 6% of the building construction cost respectively. Any inundation of depth > 0.25 meter for more than a day is expected to cause a minimum threshold proportional damage requiring repair that varies with the type of the building. Any building submerged for 10 days or longer at an inundation depth greater than 1.5 m would always require repair. The proportion of buildings needing repair decreases linearly for fewer days of inundation. Proportion of damage differs across inundation depth ranges. 08/12/2016 14#15Clean-up Cost of Residential Building: Methodology It is assumed that all inundated buildings not requiring repair will incur clean-up costs. Clean-up costs mainly involve disinfecting building premises and minor repairs including cleaning of the floor, whitewashing walls etc. ■ Based on field surveys, Clean-up costs are assessed to be around Tk. 500 for jhupri, kutcha and semi-pucca structures, and Tk. 1000, Tk. 2,000 and Tk. 4,000 respectively for EWS, MIG, and HIG buildings. ■ The building clean-up costs are then extrapolated to 2050 costs. Damage of Residential Property: Methodology Extensive residential property damage is caused by sudden & prolonged flooding, especially if household property cannot be moved to upper floors. Building Blocks: The damage to residential property is estimated based on the total property exposed to inundation in the first floor times a property damage factor. The estimate of residential property is based on the household income in Dhaka. In particular, it is assumed that the value of the property owned depends on the savings accumulated in each income category over a 5 year period. Savings rate differs across income groups. ■ The property damage factor is based on the depth and duration of flooding. Based on observation, it is assumed that a maximum of 33% of household property will be damaged if buildings are submerged for 10 or more days with inundation depth > 1.5 m with proportional decrease for fewer days of inundation. The corresponding maximum damage for depths 0.75 m - 1.5 m and 0.25 m - 0.75 m are assumed to be 25% and 20%. 08/12/2016 15#16Location-specific Vulnerability Assessment Hydrological modeling provided location-specific estimates of the depth, duration and extent of flooding. The impact of inundation of even the same depth and duration on population and infrastructure differ significantly depending on an affected area's disaster resilience. The climate disaster resilience of Dhaka City at ward and thana level were quantified with 125 variables (25 components along five dimensions physical, social, economic, institutional and natural). Survey data was collected and experts were consulted to quantify location-specific disaster resilience. Top 10 Flood-Vulnerable Wards Kallyanpur DND 09 87 Old Dhaka 82 DND 86 Central Dhaka 25* Kallyanpur 10 Kallyanpur 58 DND 88 DND 90 Eastern Dhaka Khilgaon outside DNCC Flood extent, Flood duration, high Population density, high population of informal settlers, high number of children and elderly, low literacy rate, low access to internet, lower number of public awareness programs/ disaster drills, Education and awareness, low level of community participation, low ability to reach consensus, inadequate interaction between social class, 08/12/2016 16#17Current Climate Adaptation Deficit * Beyond improvements in drainage infrastructure already planned and proposed, additional structural measures (pumps, sluice gates, storm-water pipes) will be necessary to mitigate waterlogging even without climate change. From the hydrological modeling simulations, the study recommended a list of investment options for each study area to reduce inundation depth to 4-8 inches within 12 hours. The cost of mitigating Dhaka's waterlogging even without climate change would cost Tk. 2.7 billion. NOTE: Tk 2.7 billion is equivalent to only 0.35% of the govt's development budget in 2014-2015. Climate Change Impacts Rainfall in Ganga-Brahmaputra-Meghna basin is expected to be more erratic with climate change. More intense rainfall is expected in the coming decades. Intense rainfall events are expected to be more frequent. Climate Change Rainfall is approximated by 16 percent increase in 24-hour rainfall in Dhaka in 2050 as compared to the baseline. Adaptation to climate change would require an additional investment of Tk 1.3 billion. 08/12/2016 17#18Cost-Benefit Comparison Potential cumulative damage from intense rainfall events between 2014 and 2050 even without climate change is Tk 110 billion. Potential cumulative damage from intense rainfall events between 2014 and 2050 with climate change is Tk 139 billion. With recommended Tk 2.7 billion investment made to mitigate the historic September 2004 waterlogging in current climate: ■ Potential cumulative damage will reduce to Tk 37 billion without climate change. ■ Potential cumulative damage will reduce to Tk 49 billion with climate change. ▪ This estimate of potential savings in damage is conservative. Message to Policy Makers Invest to address historic waterlogging in the current climate - the city is already facing the risk even without climate change. Benefits of these recommended investments to mitigate waterlogging in current climate exist even in the absence of climate change, making such investments an attractive low-regret option. Develop additional measures to mitigate climate risks sequentially after addressing the current climate risks. Climate and disaster resilience is not uniform in all parts of megacity Dhaka. There is room to improve local disaster resilience. Facilitate area- specific action planning for strengthening the local climate disaster resilience. 08/12/2016 18#19Complementary Flood-mitigation Measures Routine Cleaning of Drains: Sludge Removal ☐ Hydraulic Jetting and Vacuum Suction Machines for DWASA and DCC (8 sets for Tk 120 million each) Remote-Controlled Excavators for DWASA (3 machines for Tk 40 million each) Shaving Peak Flow ■ Green Roofs ■ Management of Impervious Surfaces Use of Water Bodies as Detention Ponds Last Resort: Truck-Mounted Water Pumps Book Launch World Bank, Dhaka 23 November 2015 Can be downloaded from: https://openknowledge.worldbank.org/handle/10986/22768 DIRECTIONS IN DEVELOPMENT Environment and Sustainable Development Urban Flooding of Greater Dhaka in a Changing Climate Building Local Resilience to Disaster Risk Susmita Dasgupta, Asif Zaman, Subhendu Roy, Mainul Huq, Sarwar Jahan, and Ainun Nishat WORLD BANK GROUP 08/12/2016 19#20Book Launch World Bank, Dhaka - 23 November 2015 শাওন হাসনাত জ্যেষ্ঠ প্রতিবেদক INDEPENDENT STAF 127/2 TROY রাজধানীর জলাবদ্ধতা BALCON রণ কোটি টাকা বিনিয়োগে তা কমবে ৬৫ ভা Man held for possession of 2,000 Yabe tablets in Gopalganj AMUNA জাতীয় প্রধান আসামি নূর হোসেনকে হাজিরা শেষে কারাগারে র Book Launch World Bank, Dhaka - 23 November 2015 08/12/2016 20 20#21Potential Use of the Book This analytical work will assist to mitigate current waterlogging and to further climate-proof drainage infrastructure in Greater Dhaka Area. Recommended list of investment options will help decision-makers to formulate more effective flood- control strategies, prioritize interventions, and sequence activities as resources permit. Identified priority zones and priority sectors to improve disaster resilience. Facilitate area-specific action planning for strengthening the local climate disaster resilience. Major reference resource for researchers, practitioners and students. Bangladesh Development Series Report: Climate Disaster Resilience of Greater Dhaka Area A Micro Level Analysis Climate and disaster resilience is not uniform in all parts of megacity Dhaka. Variations result from spatial differences in the strengths and weaknesses of the economic, social, physical, institutional or natural aspects. - The climate disaster resilience of Dhaka City in its seven drainage zones at ward and thana level was quantified with the planning tool CDRI developed by the Kyoto University. To compute Dhaka's CDRI with 125 variables (25 components along five dimensions physical, social, economic, institutional and natural), survey data was collected and experts were consulted. 08/12/2016 21#22Findings Overall, Dhaka city has moderate level of disaster resilience. There is room to improve disaster resilience by Improving governance Mainstreaming Disaster Risk Reduction and Climate Change Adaptation ■ Management and Dissemination of knowledge ■ Effectiveness of the Crisis Management Framework Central Dhaka has the highest CDRI. DND area has the lowest CDRI. Potential Use Identify priority zones and priority sectors to improve disaster resilience. Identify specific potentials of different localities that other areas can learn from. Identify specific weaknesses localities to improve upon. of different Facilitate area-specific action planning for strengthening the local climate disaster resilience. Facilitate integration of Climate Change Adaptation with the Disaster Management Plans and Urban Development Plans of the Greater Dhaka Area. 08/12/2016 22#23Timeline 08/12/2016 April 2012: June 2012: April 2013: May 2013: June 2014: Review and Approval of Concept Note Consultative Workshop #1 (Presentation of methodology) Consultative Workshop # 2 (Hydrological Modeling Results on Climate Change Impacts) Focus Group Discussion #1 (Recommendation of Location-specific Adaptation Measures) Technical Review of the Report by Local Experts August 2014: Consultative Workshop # 3 (Presentation of the Study Results) August 2014: Focus Group Discussion #2 (Discussion of Flood Mitigation Policy) March 2015: Review of the Book by International and Bangladeshi Reviewers November 2015: Launch of the Book and the BDS Report Special Acknowledgement - BCCRF Funding Mr. Mahbub Rahman, Director, Water Resources Planning Division, IWM Mr. Kazi Habibullah, Executive Engineer, D-WASA Mr. Liakath Ali, Climate Change and Environmental Advisor, DFID - Bangladesh Ms. Norma Adams, Book Editor Ms. Polly Adams, Graphics Editor, World Bank Ms. Angie Harney, Program Assistant, World Bank 23 23#24Report Launch World Bank, Dhaka 23 November 2015 THE WORLD BANK BANGLADESH Development Series 08/12/2016 Can be downloaded from: http://documents.worldbank.org/curated/en/2015/11/ 25477835/climate-disaster-resilience-greater-dhaka- area-micro-level-analysis Climate and Disaster Resilience of Greater Dhaka Area: A Micro Level Analysis 24 24