International Conference in Urban and Regional Planning "Planning towards Sustainability and Resilience" 14 – 15 March, 2018 ,

Flood risk assessment for sustainable urban development : Case study of --San Juan river basin, Manila

Mohamed KEFI , PhD Dr. Binaya Kumar MISHRA, Dr. Yoshifumi MASAGO

March 14th, 2018 2 Water and Urban Initiative project (WUI) Overall objectives • Contribute to evidence-based policymaking for sustainable water environments by assessing their values in Asian cities ◦ Provide scientific tools to forecast the future state of urban water environments ◦ Support capacity development aiming at improving urban water environments Research components

Future Projections Economic evaluation Policy Recommendations 1. Flood inundation 1. Flood damage 1. Flood control 2. Urban water quality 2. Value of improving 2. Wastewater management 3. Flood-related infectious water quality diseases 3. Low carbon technologies in WWTPs

Project period • August 2014 – March 2018 3 Background : Global Natural Disaster (1) 2016 : 750 natural events and USD 175 Bn

Overall Losses Events

32% 50%

Hydrological disasters include flood and landsides. This group is the most important class of natural disaster

(Munich RE, 2017) 4 Background : Global Natural Disaster (2)

Events Overall Losses

Asian regions are considered as the most exposed areas in the world to natural disasters

(Munich RE, 2017) 5 Background : Flood - Frequency and intensity of natural disasters such as flood events are increasing - Unplanned Land use and climate change are the main drivers to the rise of flood events - Increasing flood events can conduct to heavy damages with negative social and economic impact - Asian Regions such as the Philippines are considered as the most exposed areas in the word to flood hazard - Typhon Ondoy hit many regions ( Island) in September 2009. 4.75 Million persons were affected and more than 155,000 houses were damaged in totally or partially (NDCC, 2009)

(Ondoy 2009, Marikina DRRM) (Ondoy 2009, Marikina DRRM) (Ondoy 2009, LLDA) 6 Objectives To explore feasible options for flood risk management towards improving urban water environment of Manila

• Establishment of flood models (hydrologic and hydraulic) for future flood assessment in Manila • Scenarios development for climate and landuse change considerations and alternative countermeasures • Evaluate the future tangible flood damages in 2030 using spatial analysis approach 7 Overview of the methodology • Flood risk assessment Components

Hazard Exposure Vulnerability

Tools Land Use Flood simulation Flood damage map/Replacememt (FLO-2D) functions cost Parameters

Flood water depth Asset Susceptibility of the based on Return exposed/Element at exposed assets at Period risk value contact with water

Flood Damage assessment -Climate Change (RCPs and GCMs) Hypothesis : 1- Assessment of flood damage at Meso-scale -Topography (DEM) Data -Soil type 2- Built-up class is applied as an aggregated land use categories -Land Use Change using Land Change 3- Property value is assumed to be the replacement cost of degraded assets Modeler (LCM) and LANDSAT products -Stromwater Infrastructure Raster-based GIS approach

FLO-2D Software Calibration/Validation Local property value data Inundated areas/Flood Depth Comp.1

Overlay Affected LULC Flood Damage map at grid level Comp.2 Land Use Land Cover (LULC) Total Damage per grid = 2015 - 2030 Damage rate X Affected area X Unit property value

Land Use Flood Damage rate Classification/LCM Scenarios/Future for built-up Assessment LANDSAT (Depth damage function) Comp.3 Grid size : 100 m Flood simulation : 100 years return period 9 Study Area

Marikina-Pasig-San Juan River system

Hydrologic modeling area 401 Km2

Inundation modeling area 334 Km2 10 Modeling Approach 1- Hazard Inundation modeling : Model set up 1- Hazard

• Ondoy flood event was used for calibration of the flood inundation model • Peak discharge at St Nino for 2009 flood was about 3500 m3/s (considering upstream inundation). Simulated flood was 3413 m3/s

• Damage analysis Inundation model set up at FLO-2D platform 12 Land Use projection Projection of future land use based on past data using 2- Exposure Land Change Modeler (LCM)

Land Use 2014 • Landsat 7 ETM • Land Change Modeler (LCM) • 03/04/2002 • Landsat 8 OLI/TIRS • Factors : • Supervised • 07/02/2014 Classification Elevation/Slope • Supervised Classification Land Use 2002 Land Use 2030 13 Flood Damage function 3-Vulnerability • Flood damage Depth function is graphical relationships of the losses expected at a specified depth of flood water • Physical damage : Flood depth function derived from field survey

Data collection from Barangays 14 Scenarios Analysis

Climate and land use Scenario 1 : Business as Usual change Current situation

Scenario 2 :With Mitigation Countermeasures

Countermeasures: Dam (75 MCM), greater flow capacity (600 to 1200 m3/s of ), infiltration measures and flood canal diversion (with full capacity 2400 m3/s instead of 1600 m3/s Climate Change (Average Daily rainfall during Ondoy typhoon (2009) estimated to 356.8 mm) Daily maximum rainfall for current and future climate (2020-2044) Return period RCP 45 RCP85 (Year) Current MRI MIROC MRI MIROC 50 322.0 370.1 375.1 402.4 451.0 100 360.8 411.6 425.9 449.6 516.5 15 Result : Comparison of flood inundations

Current 1- Hazard

Manila City

Business-as-Usual

30% increase of Peak Discharge

Pasig City/Taytay With Mitigation Montalban for current and future conditions 16 Comparison of flood inundations 1- Hazard

-47%

+94%

Comparison of current and future conditions pointed out an increase of 94% in Business as usual scenario and a reduction with 47% with the implementation of specific measures 17 Land use land cover (LULC) change

2014 2030 18 Result : LULCC analysis

2- Exposure Urban will Increase by 10%

Urban area will increase  Exposure to floods will increase 19 Result : LULCC by City

2- Exposure

Manila

-

Metro

Urbanization of some cities of Rizal in Future 20 Flood Damage function 3-Vulnerability

Logistic model (2 parameters)

Flood depth function for built-up Nonlinear regression*

ퟏ 푫풂풎풂품풆 풓풂풕풆(%) = (ퟏ + 푬풙풑(+ퟒ. ퟖퟗퟒ − ퟏ. ퟕퟑퟓ ∗ 푫풆풑풕풉) R² = 0.980

(*XLSTAT) 21 Flood Damage Assessment 2

Current Situation (2015) Total Damage : 212%

1 3

Business-as-usual (2030)

81 Millions USD

1/ The damage is important in Manila and Pasig City

2/ Total damage in Rodriguez and Legend San Mateo will be significant in the Flood Damage per grid future No Damage < 10,000 3/ Serious damages along Marikina 10,000 - 25,000 25,000 - 50,000 Mitigation (2030) and San Juan river > 50,000 22 Flood Damage vs Flood Hazard Damage related to Depth

Low risk

Damage related Damage along Low protection to urbanization river

Flood measures will contribute to reduce the impact of flood damage. 23 Conclusion • The climate change projections revealed an increase of 25% and in 100-yrs daily maximum precipitation ; • The effect of the projected climate change in 2030 can increase peak discharge by 30% at Montalban from 4000 m3/s to 5300 m3/s for 100-yrs return period ; • The climate scenario reveals : 94% increase in inundation area for 100 years return period (> 1.5 Depth). Flood damage will increase by 212% ; • The implementation of combined flood risk reduction will decrease flood damage by 35% comparing to current situation ; 24 Recommendations (1) 1-Marikina-Pasig-San Juan rivers runs through cities which will increase their susceptibility to flood such as Marikina city  Revitalization of the river can be a solution to avoid risk to population and buildings 2-Manila, Pasig, Taytay and are prone to floods  Hard and soft flood measures will contribute to reduce flood hazard 3-Flood damage will increase in Rodriguez and San Mateo. It is mainly due to urbanization which will increase the vulnerability of these cities  Effective urban resilience strategies should be adopted 4- More attention to San Juan river 25 Recommendations (2) • High resolution simulations, more accurate land use, additional GCMs/RCPs are expected to increase the accuracy of the results of flood hazard ;

• Improvement of flood databases can conduct to reduce the degree of uncertainty ;

• Flood damage can be more accurate with the use of high- resolution satellite images and the establishment of flood depth function for different land use type ; 26 Contribution to SDGs

Target 1.5: Build the resilience of the poor and those in vulnerable situations and reduce their exposure and vulnerability to climate- related extreme events and other economic, social and environmental shocks and disaster

Target 11.3: Enhance inclusive and sustainable urbanization Target 11.5: Significantly reduce the number of deaths and people affected and direct economic losses caused by water-related disasters

Target 13.1: Strengthen resilience and adaptive capacity to climate- related hazards and natural disasters Target 13.2: Integrate climate change measures into national policies, strategies and planning Thank you!