Disaster events based dynamic risk assessment system for Nepal

Transcription

1 Hari Krishna DHONJU, Deepak Raj AWASTHI, Deo Raj GURUNG Key words: Disaster, risk assessment, webgis, SDI SUMMARY Natural disaster is inevitable phenomenon. Awareness on frequency, scale of loss (casualty and property) and nature of any disaster event are important for preparedness to cope with the consequences of such disaster before and after its occurrence. In this context, capability of recent development on webgis and Spatial Data Infrastructure (SDI) system can provide a good platform for disseminating statistics and status of historical disaster events and their assessment. Based on these events, preliminary risk assessment on vulnerability, hazard and risk can be assessed dynamically and disseminate instantly. This paper presents on the design and development of the interactive web based distributed webgis and SDI system within open source Geographic Information System (GIS). The system covers to provide national, district and vdc level information on historical disaster events, their interacting mapping on distribution of economic and physical loss. The system is equipped with criteria based dynamic risk assessment for a given weight to each of the risk parameter, which can be used for future disaster preparedness, planning, spatial decision making and disaster risk reduction processes. 1/10

2 Hari Krishna DHONJU, Deepak Raj AWASTHI, Deo Raj GURUNG 1. INTRODUCTION Nepal is a landlocked country with the population of 26 million people and majority of population about 85% lives in rural area (CBS, 2011). The people of Nepal are exposed to perennial local disaster events and profound vulnerability to disasters. Nepal s disaster events based on Disaster Information Management System (DIMS, 2015), indicates that Nepal is prone to a plethora of natural and human induced calamities. The major disaster events include fire, flood and landslide, thunderbolt, flood, landslide, windstorm, rainfall, epidemic, cold wave, hail stone, earthquake, avalanche, boat capsize, air crash, drought and bridge collapse (MoHA & DPNet, 2009). The impact of these disasters is similar and resulting to loss of lives and property. In Nepal, vulnerability, hazard and risk (VHR) due to disaster are deeply complex and diverse over the country. The disaster events and its impact are increasing as they are linked to factors such as weak governance, population growth, rapid urban expansion relatively weak landuse planning, the spread of informal settlement, poor construction methods, steep land farming practices, encroachment of settlements into river plain and forest areas, and environmental degradation(aryal, 2012a). Lavell and Lavell (2009) highlighted the importance of past disaster incidents for current and future local development planning on local disaster risk reduction process. Similarly, Aryal (2012b) discussed impacts can be reduced by reviewing the scope and distribution of past disaster events. For mitigating and disaster risk reduction processes towards planning and development, knowledge of risk is of paramount importance. Disaster risk assessment in Nepal has not been undertaken to date using historical disaster events. Learning from the history of disaster events can assist academics, decision makers, planners, policy makers, and emergency responders to address vulnerability, hazard and risk to achieve affective disaster response systems in Nepal. Therefore, exploring disaster vulnerability (O Brien et al., 2008), hazard and risk assessment specific to geographical location is an important starting point towards building resilience and disaster risk reduction processes. Using instance maps to visualize data can make more easier and quicker interpretation of complex phenomena (Elliott & Wartenberg, 2004), identify patterns, and aid in planning, resource allocations for policy and decision making (Cromley & Cromley, 1996). In recent development, Geographical Information System (GIS) have made a common platform for the mapping with capability of large range of online applications. The rapid growth, accessibility and popularity of the internet and the growing public interest in accessing spatial information, combined to develop a large number of web mapping applications (Miler et al., 2010) through free and open internet GIS. The rapid development of internet technology and web GIS applications encouraged to standardize the implementation of the web map server interface. The Open Geospatial 2/10

3 Consortium (OGC) first published a specification in 1999 (Scharl & Tochtermann, 2009) and later with the name of Web Map Server Interface Implementation Specification in 2000 (de La Beaujardiere, 2006). Recently, the web map server can provide one or more of the OGC service types; web map service (WMS), web feature service (WFS) and web coverage service (WCS). Nowadays, there have been many systems which use open source web GIS methods, for example, a mapping system which shares biodiversity information (Greene et al., 2007), a support tool for assessing the implementation of cross-border and global health spatial information systems (CBHSIS) across the US-Mexico border (Moreno Sanchez et al., 2007), recently Disaster Information Management System (DIMS, 2015) which facilitates to visualize historical disaster events via maps, table and chart, and a flash flood based web GIS solution which was developed in Australia, facilitates users to map their own data online by importing tables (Glover & Jenkins, 2011). This paper specifically discusses the design, development and implementation of a web based GIS with capability of dynamic visualization for maps, table and graphs, developed under open source GIS technology. This web application facilitates the tools which have the ability to visualize distribution of vulnerability, hazard and risk in district level and village development committee (vdc) level based on historical disaster events, socio-economic and physiographic data. Moreover, it also provides a tool to choose different weighs for various variables to observe the change scenario of vulnerability, hazard and risk. The web application is designed and developed in such a way that it can be fitted to the task, interactive and user friendly, and require no expert knowledge of GIS to use. 2. MATERIALS AND METHODS Three categories of data; historical disaster events, socio-economic and physiographic data have been used for risk assessment for dynamic web mapping of vulnerability, hazard and risk. The following table presents the name of the dataset/variable, description and source used for backend database building. Table 1: Datasets/variables used for risk assessment SN Dataset/Variable Description Source 1 Disaster_events Historical Disaster events MoHA 2 Cement_RCC_Houses Household in RCC houses (CBS, 2011) 3 Drink_water Household with drinking water (CBS, 2011) 4 Toilet Household with toilet (CBS, 2011) 5 Information Household with access to information (CBS, 2011) 6 Transport Household with access to transport (CBS, 2011) 7 SLC & equivalent Educated SLS or Equivalent (CBS, 2011) 8 Population Population (CBS, 2011) 9 Sex_ratio Sex ratio (CBS, 2011) 10 pop_abroad Population in abroad (CBS, 2011) 11 Total_dep_ratio Total dependency ratio (CBS, 2011) 12 Child_woma_ ratio Child women ratio (CBS, 2011) 13 Road_den Road network density ICIMOD 3/10

4 SN Dataset/Variable Description Source 14 Health_facility Number of health facility (CBS, 2011) 15 Flood_freq Number of flood events ICIMOD 16 HAND_Den Height above nearest drainage density ICIMOD 17 RIV_Den River network density ICIMOD 18 Forest_Den Forest density ICIMOD 2.1 Computation of Vulnerability, Hazard and Risk (VHR) Vulnerability is the function of exposure, sensitivity and resilience. Population is considered as the exposure. Sensitivity is calculated as the algebraic sum of sex ratio, total dependence ratio and child women ratio. Similarly, Resilience is calculated as the algebraic sum of road density, population in abroad, educated SLC or equivalent, access to transportation, access to information, facilitated with toilet, facilitated with drinking water, household in RCC cemented houses and access to health facility...1 Hazard can be expressed as the function of frequency of disaster event type, height above nearest drainage (HAND) density, river density and forest density. If frequency of flood event is a particular disaster event type, then Hazard can be defined by equation 2..2 Then, risk due to the particular disaster event type can be defined as the product of vulnerability and hazard, is given by equation 3..3 Based on above datasets/ variables and equations (1), (2) and (3), VHR are computed dynamically in server side and publishes map in the web application. If frequency of the particular disaster event type changes upon data updates, the values of VHR also changes and consequently online map also updated dynamically (for more details, see in section 3). 2.2 System Development The development of distributed GIS based web application was done via a bottom-up approach and was accomplished in three steps: 1. System requirement analysis 2. System design and software selection 3. Application development and implementation System Requirement Analysis The system requirement is considered as the needs in the user or client and server side including development platform. In other words, the user can be able to easily interact with the web application and, visualize map and query data in tabular or graphical form as per needed in user friendly environment. This step is to acquire information about determining 4/10

5 Request Response DBMS Geospatial Server Request Response User/Client tier which features are essentials and which would be good to have for further querying and analysis of data. To make the system user friendly and interactive, the user with little or no knowledge with GIS also considered so that they can also be able use the web application. The whole system was designed and developed in free and open source system System Design and software selection The system has been designed under free and open source system. No additional software would be required on the user side and web interface would be interactive and user friendly environment. The information promulgation system is the web GIS system with the standard web server/browser. Basically, a web GIS system consists of three servers: DBMS/database server, map server and web server (see Figure 1). Database server takes care of data storage and management, map server in charge of rendering maps based on user s requests and complicated spatial analysis in the application server side and web server is responsible for providing www service. User can have access to the system with the compatible browser with different web applications tools; zoom, pan, indentify, visualize maps, query data and visualize data in tabular or graphical forms. User/Browser Internet Spatial data publishing server (Web server, Map Server and application server) Spatial data Relation Non-Spatial data Figure 1: Framework for web GIS with three components (DBMS/Geodatabase, Map server and Web server/viewer) Database essentially consists of spatial non-spatial data. District and VDC boundaries are spatial in nature where socio-economic and physiographic datasets are non- spatial datasets. These both categories of datasets are integrated to make geodatabase. Two open source geodatabases: MySQL and PostgreSQL/PostGIS are popular for database management system (DBMS). Though both database systems are very powerful in spatial support systems, PostgreSQL/PostGIS seem to have a larger range of spatial functionality (Cross Compare, 5/10

6 2012) and uses potentially by many of recent web GIS solutions(anderson & Deoliveira, 2007; Evans & Sabel, 2012; Greene et al., 2007; MacEachren et al., 2008; Toutant et al., 2011). Hence, the authors choose this geodatabase for implementation. The map server bridges between database server and web browsers, which makes possible to access and display spatially enabled data as a map layer and enable querying and spatial analysis of displayed data (Anderson & Deoliveira, 2007). MapServer and GeoServer are both similar type of open source map servers. GeoServer was chosen due to its ease of administration to aid in testing and development of the system. The main criterion for choosing web server/viewer was that no additional software would be required in the client side so that user can easily visualize spatial data within standard web browser. The OpenLayers javacript library (Schmidt, 2008) makes possible for the users to visualize and interact with spatial data within the browser, which interacts with GeoServer. Similary, PHP Scripting was devised in server side to interact with table data in the geodatabase and the user request Application development and implementation After the system components have been selected, the geodatabase is designed in PostgreSQL/PostGIS, spatially enabled data are published via GeoServer and application interface is developed in html/javascript/php environments. The system has been tested for each criteria of requirement analysis before deploying the system. For example, correct results while computing the disaster event type frequency and corresponding VHR indices. The proper mapping of the VHR in district and VDC level based on given weight for each of the socio-economic and physiographic variables. Then, main three things were considered during development processes such as interpreting the results and maps based on the query, visualize and interact with the data, and use proper point or polygon choropleth. The overall system development is discussed in more detail in the following sections. 3. RESULTS AND DISCUSSION In this section, the complete design of the finalized web GIS system and its operation is discussed. The overall system flow diagram is shown in Figure 2, is divided into three vertical columns; the server side in the left, web server in the middle and client/user side in the right. The system has distinctly two ways to work with: 1) Visualization for dynamic VHR maps based on user defined query and different weights for both socio-economic and physiographic variables. 2) Visualization of request data in the form of tabular and graph. For visualization of disaster events based dynamic VHR maps for a given user defined query, one should go through bottom-left to web server, then to GeoServer and geodatabase. If individual weights area to be used for each of the socio-economic and physiographic variables, the same path should follow. Similarly, for visualizing the requested data in tabular and graphical form, one shall follow from left-top to web server, then to building PHP script and geodatabase. 6/10

7 When the web application is browsed for VHR maps visualization, a request is sent from the tool to GeoServer via web server to render request data in the map viewer. The request data are transmitted from server to client side as vector (WFS) or as image (WMS) as discussed in the previous sections. The amount of time taken is depends on the size of the information required to be transmitted from server to client side and the level of possible interaction with the data and its format. Figure 2: System flow diagram (SFD). The system is divided into three columns, server side (left), web server (middle) and a client/user side (right). The overall interface and design of GIS based web application consists of 1) a toolbar with functionalities of basic GIS functions like zoom, pan, identify and show/hide floating windows, 2) Query window with the title of Multi Level Risk Assessment (MLRA) with the functionalities of view map, view chart & table and visualize maps based on user specific weights to the socio-economic and physiographic variables and other floating windows for table of contents (All Layers), Legends, base layer switcher, etc. The sample of web application layout is shown in Figure 3. By default, the web application shows the district level hazard distribution due to flood events in Nepal. The map can be visualized polygon base choropleth mode and point size based. Higher the point size or darker the choropleth shows the high degree of VHR and vice versa. 7/10

8 B C A C D Figure 3: Web application layout. The web application interface is labeled into four regions from A to D. A: map display/visualization component, B: toolbar, C: query window and table of content or layer list window and D: base layer switcher window. By default, the application shows hazard distribution due to flood event in district level over the country. The accuracy of VHR distribution map solely depends on the collection, entry of disaster events data and ingestion into the geodatabase, which also propagates the error in computing the frequency of the particular disaster event type. Similarly, the VHR distribution map also depends on the socio-economic and physiographic variables whose accuracy also depends on its positional errors and effect of scale used while generating such datasets. The web based GIS application is developed fully in free and open source system (FOSS). Though many web systems are using alternative open source web GIS, the system is not free from some of the underlying difficulties associated with developing in open source when compared to enterprise one. The open source system often requires a bit long duration of time and computational expertise (Maclachlan et al., 2007) and the professional supports depends on the maturity of application and size of the user community (Steiniger & Bocher, 2009). Beside these, it is the low cost and highly customizable as per user need which silently makes it an appealing alternative for many developers and users. 4. CONCLUSION The web based GIS application is successfully developed in free and open source system for disaster events based dynamic risk assessment system for Nepal. The developed application enables users to visualize dynamically spatial distribution of vulnerability, hazard and risk (VHR) within a browser without any additional software and training. The complexity of development system and professional expertise needed for development are hidden from the user and with little or without knowledge of GIS user can use this system easily in interactive and user friendly environments. The online system can be access via link The system can be used for future disaster preparedness, planning, spatial decision making and disaster risk reduction processes 8/10

9 Initially, the system may be complicated to implement in comparison to the enterprise and commercial software solutions. However, if professional expertise is readily available, the development process is straight forward and cost effective in long run. Moreover, the user communities of open source system are also growing though forums and these large communities are devoted to help and share ideas which can motivate to solve the problems instantly which may not be possible in closed source application development. ACKNOWLEDGEMENTS The authors gratefully acknowledge International Centre for Integrated Mountain Development (ICIMOD) for providing financial support and essential datasets for this research. We would also like to acknowledge the contributions from many colleagues in ICIMOD to allow us to conduct this research and present in the wider audience. REFERENCES Anderson, B., & Deoliveira, J. (2007). WMS Performance Tests! Mapserver & Geoserver. Free and Open Source Software for Geospatial. Aryal, K. R. (2012a). Getting down to local level: exploring vulnerability to improve disaster management systems in Nepal. Northumbria University. Aryal, K. R. (2012b). The history of disaster incidents and impacts in Nepal International Journal of Disaster Risk Science, 3(3), CBS. (2011). Retrieved September 30, from Cromley, E., & Cromley, R. (1996). An analysis of alternative classification schemes for medical atlas mapping. European Journal of Cancer, 32(9), Cross Compare, S. (2012). Server 2008 Spatial, PostgreSQL/PostGIS , MySQL 5-6. Boston GIS website. Retrieved May, 7. de La Beaujardiere, J. (2006). OpenGIS Web Map Server Implementation Specification. Open Geospatial Consortium Inc., OGC, DIMS. (2015). Retrieved September 30, 2015, from Elliott, P., & Wartenberg, D. (2004). Spatial epidemiology: current approaches and future challenges. Environmental health perspectives, Evans, B., & Sabel, C. E. (2012). Open-Source web-based geographical information system for health exposure assessment. International journal of health geographics, 11(1), 2. Glover, J., & Jenkins, P. (2011). Map Your Own Data: Supporting Community Action. Paper presented at the Proceedings 14th International Medical Geography Symposium (IMGS), Durham, UK. Greene, S. L., Minoura, T., Steiner, J. J., & Pentacost, G. (2007). WebGRMS: Prototype software for web-based mapping of biological collections. Biodiversity and conservation, 16(9), Lavell, A., & Lavell, C. (2009). Local disaster risk reduction: lessons from the Andes. Lima; Comunidad Andina. Secretaría GeneralComunidad Andina. CAPRADEProyecto Apoyo a la Prevención de Desastres en la Comunidad Andina-PREDECANComisión Europea; Jun MacEachren, A. M., Crawford, S., Akella, M., & Lengerich, G. (2008). Design and implementation of a model, web-based, GIS-enabled cancer atlas. The Cartographic Journal, 45(4), /10

10 Maclachlan, J. C., Jerrett, M., Abernathy, T., Sears, M., & Bunch, M. J. (2007). Mapping health on the Internet: A new tool for environmental justice and public health research. Health & place, 13(1), Miler, M., Odobašić, D., & Medak, D. (2010). Efficient Web-GIS Solution based on Open Source Technologies: Case-Study of Urban Planning and Management of the City of Zagreb, Croatia. Paper presented at the The XXIV FIG International Congress Facing the Challenges Building the Capacity. MoHA, & DPNet. (2009). National Disaster Report 2009: The Hazards and Vulnerability: Kathmandu: Ministry of Home Affairs (MoHA) and National Disaster Preparedness Network, Nepal (DPNet). Moreno Sanchez, R., Anderson, G., Cruz, J., & Hayden, M. (2007). The potential for the use of Open Source Software and Open Specifications in creating Web based cross border health spatial information systems. International Journal of Geographical Information Science, 21(10), O Brien, G., O Keefe, P., & Rose, J. (2008). The vulnerable society. Area, 40(4), Scharl, A., & Tochtermann, K. (2009). The geospatial web: How geobrowsers, social software and the Web 2.0 are shaping the network society: Springer Science & Business Media. Schmidt, C. (2008). OpenLayers: Free Maps for the Web. Steiniger, S., & Bocher, E. (2009). An overview on current free and open source desktop GIS developments. International Journal of Geographical Information Science, 23(10), Toutant, S., Gosselin, P., Bélanger, D., Bustinza, R., & Rivest, S. (2011). An open source web application for the surveillance and prevention of the impacts on public health of extreme meteorological events: the SUPREME system. International journal of health geographics, 10(1), 39. BIOGRAPHICAL NOTES Hari Krishna Dhonju is currently working in International Centre for Integrated Mountain Development (ICIMOD), Khumaltar, Lalitpur, Nepal as an Associate GIS-DSS Development Specialist and he has more than 12 years of experience in engineering software/application development with major contribution in development of SW_DTM, SW_Road, HKKH DST (GIS Viewer and 3D Viewer) and GIS based web science applications. His recent interests are focused in remote sensing and GIS based desktop and web science application and spatial decision support system developments. Computer programming is his passion through which he aspires to make geospatial technology access to everybody. Beside his works, he enjoys hiking and travelling. CONTACTS Name: Mr. Hari Krishna Dhonju Institution: International Centre for Integrated Mountain Development (ICIMOD) Address: Khumaltar, Lalitpur City: Lalitpur COUNTRY: Nepal Tel Fax hari.dhonju@icimod.org Web site: 10/10