DEVELOPMENT OF ARCGIS-CUSTOMIZED TOOL FOR FLOOD RISK ASSESSMENT AND REPORT GENERATION IN BUTUAN CITY

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1 DEVELOPMENT OF ARCGIS-CUSTOMIZED TOOL FOR FLOOD RISK ASSESSMENT AND REPORT GENERATION IN BUTUAN CITY Alexander T. Demetillo, Michelle V. Japitana, Dennis Y. Villanueva and Cherry Mae P. Tulfo CLAIMS-GIS Project, College of Engineering and Information Technology, Caraga State University, Butuan City, Philippines, KEY WORDS: flood risk assessment, GIS Customization, disaster reduction ABSTRACT: Severe flooding due to frequent rain has been a recurring problem of Butuan City, being situated in a floodplain area and a city traversed by the Agusan River - that drains into Butuan Bay at the mouth of the city. Due to the commitment of the Butuan government to build awareness and formulate risk reduction and mitigation programs, Butuan City is now at the verge of finding better ways in preparing and protecting the community during flood events. Hence, a system was designed and customized within ArcGIS 9.3 software to assess the damages caused by the flood at different level of risk. This study aims to demonstrate the application of GIS customizations and utilizing integrated data like the parcel map from the City Assessor's Office (AO) and the flood map from the City Planning Development Office (CPDO) in order to provide reliable information that can aid city main movers during disaster events. The customized system, which will be mainly used by the City Disaster Risk Reduction and Management Office (DRRMO), features includes an easy data filter option, map views, and generation of printable and downloadable maps and (tabular) reports. Valuable information that will identify households affected by flood per level, the total number of household per location, and the cost of damage of properties per flood level can be determined using the customized system. Utilization of these reports, the CDRRMO can prepare appropriate evacuation route plans and rescue operations, estimate the needed relief goods for the flood-affected community, devise better mitigation plans, and can formulate sound methods and action plans for the disaster risk reduction and mitigation programs. 1. INTRODUCTION Flood is a natural phenomenon wherein a dry land is submerged into water due to excessive rain, storm surge or tidal waves, river overflow or dam breaks. This natural event would cost the entire locality to suffer danger. Flooding may wipe out an entire city or destruct the human s life support for a living such as farms and other agricultural resources, industrial livelihood establishments, profit-making products and other valuable supplies. In cases such as this, the government deploys rescue team in order to help the affected residents evacuate from their submerged houses and save their valuable items that was left. Valuable assets are wasted especially industrial and agricultural resources are damaged. Because of the severe loss during flood events, the government is alarmed and formulates mitigation plans in order to address this problem and to at least minimize damages caused by severe flood. Since nobody can stop a natural occurrence such as flood, preparation before flood event occurs is being worked out. Government has also advised relocation of the severely flood-affected residents to higher grounds in order to avoid flood encounter, avoid damages on their personal belongings and save themselves also. Construction of better drainage systems would also help minimize flooding and regular dredging of these drainage systems would also remove silt and sediment built ups that will cause clog along drainage systems. On the other hand, application of recent technologies is also realized by the community especially on the government agencies on mitigating programs and flood routes plans in preparation against hazard. The application of GIS technology has aided the government agencies in analyzing various geospatial data and dealing with difficult situations. Since flooding deals with geographic data, application of GIS into preparation and mitigation programs will greatly improve the planning and analyzing process of the decision-makers. With GIS, digital and interactive maps are used in planning and evaluation process. Automatic generation of reports for intended purposes is easily availed with the use of GIS and creation of datasets is realized. Several agencies have utilized the technology because of its geospatial supports and compatibility with the other software applications. GIS also supports visualization of the area digitally and thus, analysis can be made available efficiently.

2 1.1 The Case of Butuan City, Philippines Butuan City is located at the outlet of the Agusan River which is also surrounded by mountainous regions. This geographic location makes Butuan City to be highly susceptible to flood. The geographic location of the city suggests rigid preparation for the unexpected hazards that will probably strike. Records of typhoons that have struck Butuan City are noted especially Tropical Depression Agaton and Seniang. These typhoons have recently landed Butuan City in year During Tropical Depression Agaton (international name, Lingling), at least 46 villages in Butuan City were recorded that have been flooded. Reports about the disaster have said that more or less 3, 438 families with at least 13, 752 individuals have relocated to safe centers according to the Philippine Information Agency (PIA) Caraga. There were also families of at least 1, 470 in count of the affected villages who were not evacuating from their houses according to the Butuan City Disaster Risk Reduction and Management Office as reported by the PIA. On the other hand, during Tropical Depression Seniang (international name, Jangmi), the roads in Upper Lemon, Pigdaulan, Lower Lemon, Tagabaca, Bilay and Aupagan (areas within the floodplain of Butuan City) were impassable due to severe flood. Accessibility to transportation during the flood event is difficult. There were different scenarios during Tropical Depression Agaton that were also evident in Tropical Depression Seniang. Because this natural phenomenon can possibly result to great loss of lives and properties, preparation is best applied before this calamity will occur. Most government agencies, especially the Disaster Risk Reduction and Management (DRRM) Offices, are initiating various programs, just as to improve their services to their respective locale. Since technology is now at its verge of making human s life easier and perform digital processes and automations, the use of technologies to change and enhance the systems and protocols of the CGB is deemed necessary. Nowadays, the utilization of geographic information system is promoted not only on the geographic location of the buildings, parcels and other spatial datasets containing ownership of real properties, but also land characteristics, area of flood extent, hazard areas and other regions of interest intended for data analysis and processing. GIS, together with the ArcGIS (GIS software for creating maps) customization, will be the main tool that this study will consider to create a set of dynamic platform that will show an easy reporting system and mapping of potential at risk population of Butuan City. Hence, a development of ArcGIS-customized tool for flood risk assessment and report generation in Butuan City is initiated in order to realize aggregation of the GIS technology to answer flood risk mapping and report generation. 2. MATERIALS AND METHOD This system is designed and customized within ArcGIS 9.3 Software to assess the damages caused by the flood at different level of risk. Spatial datasets are stored in PostgreSQL Database with PostGIS extension and psqlodbc as connector for the ArcGIS and PostgreSQL database. The datasets needed are the flood map (with flood level as attributes) and the parcel map (containing the land owner, land assessment and other parcel characteristics). The customization mainly focuses on the generation of the parcels affected by the flood map depending on the parameters being set by the system user. As soon as the affected parcels have been selected, the system also generates a layout map for the result of the system. 2.1 Implementation Plan for DRRM The implementation of the system would be based on the government hierarchical actions. Since the government is targeted to be the user of the system (specifically the City DRRM Office), preparation before the typhoon or tropical depression strike the city will start on them. As soon as the weather forecast has been channeled by Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), the CGB will formulate plans, identify strategies and actions including planning evacuations routes and centers, and assess resources to aid affected households in case a flood occurs. The barangay units will implement these suggested operations, evacuation routes plan and mitigating programs with regards to the results being generated by the system.

3 2.2 Schematic Diagram Spatial datasets being used in the system are all stored in a database. In this case, the datasets needed by the system are the flood map and the parcel map. These are queried through the psqlodbc version in order to connect ArcGIS to the PostgreSQL database. The system queries for the flood and parcel map wherein level of the flood is identified first. Once the extent of the flood level is known, the two spatial datasets are intersected and the result would be affected parcels. These results are delivered through printable and downloadable maps. 2.3 Creating a Tool for Querying Affected Parcels Figure 1. Schematic Diagram of the Study The system needs an input dataset to be intersected with the parcel (land) map, in this case, the GIS customization utilized the available flood map of CGB in order to assess flooded parcels. The susceptibility level will then be inputted in order to complete the parameters. After parameters are being set, the system will count the number of parcels and display its attributes in tabulated format. Figure 2 Data input for the system parameters

4 3. RESULTS AND DISCUSSION With the parameters being inputted by the system user, spatial identification of affected parcels and generation of the reports are produced. The following discussions are the results generated by the system. 3.1 Tabular Results of the Flood-Affected Barangays The tabulated counts are based on the parcels intersected according to what level has been set. In this case, Level 1 has been selected as the water level of the flood. These parcels are counted according to the barangays. List of Affected Land Owners Total Affected Parcels Figure 3 Tabular Display and Total Number of the Affected Parcels The figures above shows the graphical user interface on what parameters are needed to be inputted to the system (Figure 2) and the display for the affected barangays (Figure 3). By having this kind of report system, given that the parcel map is the best representative map that can identify the actual occupants/land owners (considered to be the head of each household), this system implies a quick identification of the possible flood-affected areas and record possibilities of how many parcels will be flooded. As presented in the Figure 3, these counts are according to the barangays affected by flood. Thus, preparation of the how much relief goods can also be estimated that should be delivered to the possible affected citizens of the assessed barangay. Evacuation centers can also be managed and opened in order to cater the projected number of flood-affected residents. For possible relocation for the citizens living along flood-affected areas, the government can also suggest areas in Butuan City intended for them with reference to how many families are affected frequently by flood. Additional attributes like land classification can also be considered and added as parameter in the enhancement of this customized tool to readily assess the affected properties in the area according to its classification (i.e. residential, agricultural, industrial, etc.). 3.2 Identification of the Flooded Areas Assessments results are being mapped in the ArcMap 9.3 environment in order to identify the location of the affected parcels. By doing so, the system user can spatially locate areas which are affected by the hazards being evaluated with the parameters being initialized during the process. The parcels in blue polygons are identified to be the flood-affected areas and its attributes are used for the tabular reports generated for government references and rescue operations.

5 Figure 4 Automatic Selection of the Parcels being affected by the Flood

6 3.3 Generation of Map Layout of Affected Parcels General reports are needed in order to summarize certain information very fast considering time is a great factor in mitigating risks. Using manual and conventional systems, it may took long hours or days for the local agencies to generate reports, depending on their recording and filing systems. Affected areas by flood can be visually assessed and generated using the developed customized system. This feature of the system also include a convenient exporting of map layouts to various file formats like PNG, JPG or PDF. In using the customized Arcmap tools, it proves to be convenient to use for generating map layouts as report or for reference use of the end-user. Figure 5. Map Layout of the Affected Parcels as Assessment Results

7 The customized ArcMap can also generate tabulated reports for the utilization of the appropriate offices. The following figure shows the affected parcels in tabulated formats. These statistics shown in tabular form is generated from the attributes of the flood affected parcels initially utilized in the system. With these reports, it would be easy for the government offices to identify areas and families who are affected by flood, and eventually, estimation of relief goods can be identified with a reliable source of information. Figure 6 Tabular Reports in Excel and PDF Formats 4. CONCLUSION This paper demonstrated the extendable feature of ArcMap by employing programming in order to develop a customized system for flood risk assessment. The initial results of this study showed that given a reliable input maps and any hazard maps available, GIS techniques can aid in the mitigation of disaster events by way of providing tabular reports and map layouts that can be easily and quickly generated for reference of any deciding body of the government.

8 5. REFERENCES Cavaros T., Gamez E. and Mendoza L. Application of ArcGIS tools for Flood Risk Assessment. From Evans S., Gunn N. and Williams D. Use of GIS in Flood Risk Mapping. From %20flood%20risk%20Mapping.pdf. Alexander M., et al., A GIS-Based Flood Risk Assessment Tool: Supporting Flood Incident Management at the Local Scale. From Agaton: Over 3, 000 Families Displaced,