A Case Study of Greater Chennai Corporation
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Journal of Information and Computational Science ISSN: 1548-7741 Nearest Emergency Shelter location and Management using Thiessen Polygon: A Case Study of Greater Chennai Corporation R.Dhamodaran1 and V.Madha Suresh 2 1 Research Scholar, CNHDS, University of Madras, Chennai, Tamil Nadu 2 Professor, CNHDS, University of Madras, Chennai, Tamil Nadu Abstract Global balance change in climate pattern and extreme events trigged by global warming had resulted in severe disaster. The rapid urbanisation combined with unplanned growth in the city, as well as periphery resulted in increase of vulnerability. Chennai City is situated on east coast of India facing severe threat from the cyclonic storm and flood during the onset of North-East Monsoon. Due to improper planning and management of rivers & waterbodies over decades’ lead to illegal occupation, silting and polluting significantly breaking down of drainage chains. The Study focuses on identification of the nearest emergency shelter using thiessen polygon method during flood occurrence, it provides a nearest shelter which is useful during the evacuation of people from vulnerable to safe zone. The techniques adopted to delineate the sites are based on geographical information system tool (GIS) and Remote Sensing products namely; emergency shelter location, flood map, Landuse / Landcover and road network. Thiessen Polygon method was preferred to delineate the nearest emergency shelter and Overlayed with flood map to identify & assess further need of emergency shelter in region for better management and quick response during flood. The road network used to assess the accessibility based on road hierarchy. To tackle the extreme events like flood GIS and Remote Sensing is need to formulate the effective solution and improve the management practise. Keywords: Thiessen Polygon, Emergency Shelter, Flood, Geographical Information System, Remote Sensing 1. Introduction Chennai City is expanding on all three directions which indicates the increase in population, settlement density which put the people and facilities in vulnerable situation due to intensification in severity of the natural disaster (cyclone & flood). Disaster can cause breakdown of various economic activity, damaging public properties incurring loss to human life and basic amenities. In order to facilitate the vulnerable community emergency shelter is necessary to protect and recover Volume 10 Issue 2 - 2020 1423 www.joics.org Journal of Information and Computational Science ISSN: 1548-7741 they situation during the disaster (Ma, Y et.al, 2019). The 2015 flood, affected millions of people residing along the hotspot region resulting in lack of proper shelter, food which ultimately resulted in risk of health and safety during such catastrophic event. Emergency Shelter is safe house for the affected people, it is select based on number of factor like geography, connectivity, reliability or resistance to the disaster. The government of Tamil Nadu have identified the emergency shelters covering the entire Chennai City, aims to provide shelters and food to needy. It is also important to assess nearest emergency shelter to be accessed by the public based on their location and connectivity. 2. Study Area Fig 1: Study Area Chennai is the capital district of Tamil Nadu covering 424 sq.km, referred to as the "Gateway to South India," (District Profile, 2017). Chennai is formerly known as “Madras” it major commercial, cultural, heritage and educational centre in South India. Chennai is located along the shore of Bay of Bengal (East), Tiruvallur District (North) and Kancheepuram District (South). Three major river draining the city are Kosasthalaiyar (North), Coovum (Central) and Adyar (South) of which Coovum is heavily polluted followed by Adyar, artificial drainage system running parallel coast is Buckingham canal. Based on the 2011 census data, Chennai consists of 4.6 million people with density of nearly 27000 people per km2 and suburban parts of the city consists of 4 million people (District Statistical Handbook, 2016-17). In the year 2011 Chennai Boundary was increased from 174 sq.km (155 wards) to 426 sq.km (200 wards) and divided into three section namely; North Central and South. Chennai is one important economic hub of the country which also the fastest growing cities in the world with diversified economic base rested on the following sectors like automobile, software services, manufacturing, health care and financial services industries. The water demand is feed based on reservoir supply which is mainly Volume 10 Issue 2 - 2020 1424 www.joics.org Journal of Information and Computational Science ISSN: 1548-7741 dominated by the monsoonal rainfall and supply from Andhra Pradesh. Receives majority of the rainfall during the onset of Northeast monsoon and 30 % in Southwest monsoon. Climate is Hot and Humid during April to July with maximum of 41o C and minimum of 25o C recorded. 3. Material and Methods The material utilised in this study consisted of the following parameters relating to flood and emergency shelter management. The data used are emergency shelter, road network map, flood map and Landuse / Landcover map. Source of data obtained are consisting of governmental & non-governmental agency like District Disaster Management Centre, Highway Department, United States Geological Survey (USGS). The Satellite based data was corrected based on two techniques namely; radiometric and projection for removal voids, noise and converted to projection fitting to the geography (Universe Transverse Mercator, Zone - 44 N). The Landuse map was prepared using the Sentinel data and Elevation was obtained from SRTM. The flood inundation is basically proximity near to waterbodies and topography of the study area. ArcGIS was used to generate result layers and conversion of data, thiessen polygon tool was used to identify the nearest emergency shelter. Emergency shelter was converted into Shapefile and inputted into creation of polygon (Thiessen). The road network map Overlayed to assess the accessibility of the people during flood scenarios. Results can be used to locate new emergency centre based on the requirement of the people. Emergency Shelter Data Used Image Satellite Imagery Conventional Data Enhancement Sentinel Imagery DEM Emergency Shelter Road Network LULC Overlay Analysis Flood Map Nearest Emergency Shelter Fig 2: Methodology flow chart for Present Study Volume 10 Issue 2 - 2020 1425 www.joics.org Journal of Information and Computational Science ISSN: 1548-7741 Table 1: Data-used Sl. Input Data Source Scale / No. Resolution 1. LULC USGS – Sentinel-2 10 m 2. DEM USGS - SRTM 30 m 3. Emergency Shelter Chennai Corporation - 4. Road Network Chennai Corporation - 4. Result and Discussion (i) Emergency Shelter The Emergency Shelter data is obtained from Corporation of Chennai and plotted based on the shelter coordinated using the GIS Software and Google Earth. Chennai City has twenty – six shelter across fifteen zones, with the highest recorded in the central Chennai and scattered along the parts of North and South divisions. Fig 3: Emergency Shelter The Emergency Shelter (Zhao et.al 2017) is important centres providing shelter and essential Supplies (Food & Medicine) during the time of flood or disasters. The emergency shelter is selected based various functions like geography, accessibility and ability to withstand disasters. Still compared to the population of growing city the number of available shelter is lesser. (ii) Landuse / Landcover Landuse / Landcover was produced using Sentinel imagery with spatial resolution of 10 m. The imagery was error-corrected using two techniques radiometric and projection to remove the noise and project to local area projection. The Landuse / Landcover was processed using Supervised classification technique with sample used to train the computer and output is derived based on the number of trained classes (Reis 2008). Landuse / Landcover consisted of following features like fallow land, built-up, waterbodies, wasteland and vegetation. It provides the value information during flood, identifying the settlement closer to waterbodies or river, identification of safer Volume 10 Issue 2 - 2020 1426 www.joics.org Journal of Information and Computational Science ISSN: 1548-7741 location. Settlement occupies 70% of the surface area, followed by vegetation, barren land and waterbodies. Fig 4: Landuse / Landcover (iii) Flood Flood map was prepared using the terrain data download from the United States Geological Survey (USGS), the SRTM data is 30m accuracy. The low elevation was identified and in cooperated with 2015 flood level (Sanyal and Lu 2009). The weightage fixed based on the two information namely; elevation of the region and proximity towards the waterbodies or river system. Fig 5: Flood Affected Region Based on the dervired flood map the central part Chennai is affected seriously, followed by the south Chennai. The reason behind the flood severity in the region of Adyar, Saidapet, parts of Guindy, Velachery and Pallikkarani due to closer proximity to the waterbodies and improper maintains of drainage system. Volume 10 Issue 2 - 2020 1427 www.joics.org Journal of Information and Computational Science ISSN: 1548-7741 (iv) Road Network Road is vital which is considered artillery of country or city in term for supplying goods, labours, services from one place to another. Chennai is built on web of road networks covering around 6000 km starting the National Highway, State Highway and Local Roads. Roads