GIS Based Rapid Assessment for Flood Physical GIS Based Rapid Assessment for Flood Physical Vulnerability in Naga City, the PhilippinesVulnerability in Naga City, the Philippines

Methodology of rapid and cheap data collection processes in this research may help Naga Municipality or other local municipalities to repeat the similar data collection processes with a low cost investment in a wider area.

The results indicate that the structural type with plywood walls and wooden floors is the most vulnerable buildings to flooding, while the structural type with hollow block walls and concrete floors is the least vulnerable. Vulnerability of building contents is mainly determined by the number of floors. Households with a two-floor house are the least vulnerable while households with one floor house are the most vulnerable.

This research can help small municipalities to conduct a cost-effective flood vulnerability assessment and design an appropriate approach or policy for reducing flood disaster risk, such as building codes and relief materials.

This research examines the flood physical vulnerability and people’s coping mechanisms in flood prone residential areas in Naga City, the Philippines. The flood physical vulnerability includes assessment of flood damages / losses to the elements at risk, namely: structural types of building, building contents and outside properties. Mobile - geographic information system (GIS) and a digital camera were used for building inventory to create digital (attributes) data and the geo-reference. Interviews with questionnaires were conducted to collect detail information. Analyses were mainly done by flood –depth relationships (Penning-Rowsell and Chatterton, 1977; Dutta and Tingsanchali, 2003). The use of mobile GIS has speeded up the process of data collection, data input after the fieldwork and data analysis.

4. Fieldwork / Data Collection

5. Findings

(f) Scatter Plot of Flood Depth and Vulnerability of Building Contents

(Left) flood depths - vulnerability relationship without floor classification(Right) flood depths – vulnerability relationship with floor classification

2. Study LocationBarangay Sabang and Barangay IgualdadNaga City the Philippines

1. Introduction

• Fieldwork was carried out from August 19 – September 24, 2005.

This presentation is derived from an MSc thesis entitled: Analysis of Flood Physical Vulnerability in Residential Areas, Naga City, the Philippines.This work was conducted under the umbrella of Strengthening Local Authorities in Risk Management (SLARIM) research project of ITC.

The author is grateful to Paul Hofstee and Nanette Kingma in ITC who have provided supervision of this thesis. The author also thanks all the respondents from Barangay Sabang and Barangay Igualdad, Naga City who have given valuable information for this research.

This poster is presented during the Development Cooperation Prize Giving Ceremony at Royal Museum for Central Africa, June 14th 2007, Tervuren, Belgium.

Conclusion Acknowledgement

Saut Aritua Hasiholan Sagala received his MSc degree in 2006 from International Institute for Geo-Information Science and Earth Observation (ITC), Enschede, the Netherlands, where he conducted this research.

Currently he is a PhD Candidate at Department of Urban Management, Kyoto University, Japan. Email address and website:

- sagala@drs.dpri.kyoto-u.ac.jp or saut.sagala@gmail.com- http://sautsagala.wordpress.com

Nationality: Indonesian, Current residence: Kyoto, Japan

Author

Points with Attributes Collected from Building Inventory

(e) Vulnerability Map of Structural Types of BuildingsInformation from vulnerability of structural of types (d) combined with the geo-

reference information

(a) Structural Types of Buildings in the Study Area

(b) Spatial Distribution of Structural Types of BuildingsThe map is derived from the classification of structural types of buildings (a) and geo-

reference information

(d) Vulnerability Curves of Structural Types of BuildingsThe curves are developed from flood depth – damage relationships (damage in term

of percentage) while flood depths obtained from interviews

Structural Type 6Hollow Block Wall – Concrete Floor

Structural Type 5Wooden Wall – Concrete Floor

Structural Type 4Wooden Wall – Wooden Floor

Structural Type 3Bamboo Wall-Bamboo Floor

Structural Type 2Plywood Wall – Concrete Floor

Structural Type 1Plywood Wall – Wooden Floor

Checklist for Data Collection

Research Scope

Discussion with Key Contacts: Disaster management and Barangay officers

Secondary Data Collection

Primary Data Collection

Interviews to 68 households

Database:Structural Types of Building in Detail

Building Contents and Outside PropertiesFlood Depths

Damage (Losses)People Coping Mechanism’s

Mobile GIS (PDA, GPS and Digital Camera)

Building Inventory to 245 Buildings (Simple Random Sampling)

Classifications of Building Based on Wall

MaterialsReports and past

research

Analysis of the Elements at Risk

Six Structural Types

Values of Build. Contents

Values of Outside Properties

Flood Depth – Damage Relationships:• Structural Type• Building Contents• Outside Properties

Flood Depths

TIN – Interpolation of Flood Depths

obtained from Interviews

Vulnerability Curves for Structural Types of Building, Building Contents

and Outside PropertiesFlood Hazard Maps

Conclusion

People’s Coping Mechanisms with Floods

• Building Inventory with Mobile GIS (245 buildings)

Personal Digital Assistance with built-in GPS on the top

Map of 245 Points (Buildings) Collected from Building Inventory

Building inventory process was conducted in two weeks by recording building information

with Mobile GIS and a digital camera

3. Analytical Framework

Interview process was done for three weeks, asking the respondents about the structural

types in detail, building contents, outside properties, flood depths, flood damages and

coping mechanisms

• Interviews with Respondents (68)

(c) Flood Hazard Map in 1995The map is derived from the interpolation of flood depth values which were

transferred into TIN (Triangulation Irregular Network) of Flood in 1995

(g) Vulnerability Map of Building Contents and Number of Floors

This map shows the spatial pattern between vulnerability of building contents (f) and the number of floor