Earthquake vulnerability and evacuation plan for old Dhaka

Abstract

In any disaster mitigation measures an effective evacuation plan is of utmost importance in reducing the loss to a great extent. Earthquake vulnerability. assessment of an area put a great significance in preparing a successful evacuation plan considering the prevailing local condition. Such plan can make a locality self-dependent in coping with disa~t.erand minimize the risk in.time. Considering the facts it has been felt necessary to undertake a study on earthquake vulnerability assessment and evacuation plan for Old Dhaka. This report represents an enormous study on "Earthquake vulnerability and evacuation plan for Old Dhaka" that has been assigned in partial fulfillment of Master degree in Urban and Regional Planning. The study has been conducted in ward no. 68 of Old Dhaka. The ward is highly vulnerable to earthquake due to its high density of population (682 per acre in 2009), vulnerable structures, low preparedness of people etc. The unplanned development of the area with existence of old dilapidated unreinforced masonry buildings.(II% of the surveyed buildings), narrow road network, close proximity of adjacent buildings, irregular building shape and others made the locality more prone to earthquake disaster. As part of earthquake preparedness, it is essential to undertake structural vulnerability assessment of existing buildings because damaged structures are the main cause of human injury and death. From field survey of 1383 buildings, 59% building was found 1-3 storied height and 29% was found 4~5 storied in height. The .earthqM,akevulnerability assessment of the existing buildings was done following two different visual screening methods i.e. FEMA-RVS and Turkish Simple Survey (Level-I & Level-II) Procedure. 77% buildings of the study area excluding the katcha, semi-pacca and under construction buildings were surveyed using FEMA-RVS method. Buildings showing value above the cut-off score are considered seismically safe. In the study area 54% of the buildings were found below the cut-off score '2' according toFEMA 154 while considering cut-off score '1.5' with respect to our country's economic capability the number reduced to 38%. These buildings require further detail analysis by structural-engineers to be considered safe in earthquake and based on the findings future initiatives like retrofitting or others as appropriate should be done to strengthen the building. The public buildings (25 in number) were proposed to be used as post-earthquake shelters beside the available open spaces to evacuate people living in vulnerable structures. The proposed shelter building was analyzed in detail using Turkish Level-I and Level-ITmethod. Most of the proposed shelters were found below the cut-off score '50' in Turkish method. They need more detail analysis by structural engineers and proper treatment like retrofitting to strengthenthe structure and ensure its fitness and adequate functioning-during earthquake. From field survey 18;1-33populations were found who live in vulnerable buildings with a 11 ~-..------.-------.--.--~--.----~~-1 ! cut-offv~lue less than 1.5. The shelter capacity was available for 26,218 peoples considering . 10 sq ft area per person. The shelters are sufficient in number to serve the people living in risky buildings. A socio-economic questionn;:tire survey with a sample size of 210 households was done which is 2% of total projected household 10,942 in 2009 in order to find out the existing condition of the residents including. public awareness level about earthquake risk of the community and so on. Aged people, infant and women are considered more affected during earthquake. The aged people, infant and children were found 11%.where women represented 37% of total population in 2009.44% of the surveyed household feels their residing building is vulnerable to earthquake while 75% of them feel their community vulnerable to earthquake. 76% of the respondents definitely know what is earthquake. 74% of surveyed respondent perceive themselves aware of earthquake. 56% have plan to go to open space or big hall when earthquake will happen, 36% of them also have plan to take shelter under table/strong furniture and stay beside column during earthquake. So on an average 46% of the surveyed people are really aware about earthquake. As the area did not experience major earthquake it is uncertain to predict what would be the actual response of people in that time. 70% of surveyed people did not participated in any Earthquake awareness related training! seminar/ drill. They need regular awareness training to improve the situation and reduce loss due to earthquake. This study concludes with an effective evacuation plan considering the survey findings and the prevailing social and physical environment of the locality. Evacuation routes were proposed connecting the evacuation shelters with proposals of road widening up to 12 ft where necessary.-Buildings adjacent to main evacuation path are also recommended for especial consideration regarding retrofitting of vulnerable ones to, keep the route uniriterrupted during disaster and ensure free follow of outside emergency help like fire service and'others. The catchment area covered by each shelter with the shortest..s.afest -path from home to shelter was also delineated. Finally the study concludes with proposals at policy level, public awareness increasing, retrofitting of the buildings and so on. Vulnerable private buildings.need.to be retrofitted by owner's personal costing. In some cases financial help from Government can be. given. Government should enforce BNBC, setback rules by RAJUK and other planning provisions in new building construction and some times redevelopment of buildings should be done where necessary. More training, seminar, drills should be done to increase the earthquake awareness of the local people by Government and private organiZations. Thus the earthquake vulnerable situation can be improved withsuccessful implementation of proposed evacuation plan.