Incorporating earthquake risk sensitivity in landuse planning at local level

Abstract

Earthquake risks in cities are increasing due to the high rate of urbanization, unplanned growth, faulty landuse planning, poor construction practice, inadequate infrastructure, and services provision and environmental degradation. This risk is compounded due to unplanned development in high-risk areas. So, it is necessary to plan growth in terms of infrastructure and construction by taking into account hazard and risk parameters to reduce the risk. The process of mainstreaming disaster risk management parameters in land use planning is termed as Risk-sensitive Land Use Planning (RSLUP). Bangladesh is at high risk of the earthquake. Rapid and uncontrolled urbanization is increasing the exposure of Dhaka, the capital city of Bangladesh to potential earthquake. To reduce the risk, it is necessary to understand the risk sensitivity and thereby incorporate RSLUP while planning for development in Dhaka city at the local level. This research has been carried out with an aim to assess risk sensitivity of landuse at the local level and to formulate RSLUP strategies to reduce the risk accordingly. For this purpose, Uttara Residential Model Town (URMT) (third phase), Dhaka, Bangladesh has been selected as the study area. The area is in the process of development by RAJUK and is located in the high earthquake hazard prone area. So there is still scope to integrate risk sensitivity in the proposed landuse plan. Thus, the objectives of this study are: firstly, to assess the risk sensitivity of the proposed landuse plan of the study area and, secondly, to formulate RSLUP strategies to be incorporated in the proposed plan of the study area. The risk sensitivity of the proposed landuse plan of the study area was assessed in two steps. Firstly, earthquake hazard was assessed including ground shaking using RADIUS, amplification using DEEPSOIL, and liquefaction using SHAKE. Overlaying these maps, an earthquake hazard zoning map of the study area was prepared. Secondly, risk sensitivity of the proposed landuse plan of the study area was assessed under eight risk themes based on the earthquake hazard zoning map (prepared in first step). The study area is at the phase of development. So it was necessary to study the development pattern and earthquake vulnerability of buildings of a reference area assuming that similar development will take place in the study area. For this purpose, the second phase of URMT was selected. An earthquake risk sensitive zoning map of the study area was prepared by overlaying the risk theme maps using comparative weight developed using AHP. Based on the findings from risk sensitivity analysis, RSLUP strategies were formulated to be incorporated in the proposed plan of the study area through key informant interview. From the analysis of the risk sensitivity of the proposed landuse plan of the study area, it can be observed that, among four sectors in the study area (sector 15, sector 16, sector 17 and sector 18), sector 16 is comparatively more prone to earthquake hazard in the study area. Among eight risk themes, the study area has been found risk sensitive in terms of six themes, e.g. macro form risk, risks in land-use incompatibilities, risks in hazardous uses, special risk areas, risks in building stocks, and risks in critical facilities. Combining risk themes and earthquake hazard zoning of the study area, it has been found that, sector 18 is more risk sensitive though sector 16 is highly earthquake hazard prone. Thus, other risk factors have resulted in increased risk sensitivity of sector 18. The RSLUP strategies formulated based on the risk sensitivity analysis of landuse plan of the study area are: earthquake risk sensitive zoning (indicating different earthquake risk sensitive areas), development control in the high-risk sensitive zone (density control through building height restriction; tax penalty and mandatory insurance), transportation planning to ensure internal as well as external connectivity after an earthquake (extending primary roads in the south direction; road widening through land acquisition and tax incentive; preparation of traffic management plan regulating the direction of traffic movement in the road segments; waterway planning as an alternative to road transport; earthquake resilient construction of MRT, bridges and culverts), earthquake resilient landuse planning and building construction (promote mixed-use development; strengthen landuse and building approval and monitoring process considering soil condition; plan for central parking facility to discourage soft storey; risk financing for earthquake resilient building construction; capacity building of approval and monitoring team as well as workers), prevention of secondary hazards (earthquake resilient construction of hazardous uses; establish central control panel for lifeline; preparation of environment management plan; preservation of designated waterbodies), planning for critical facilities (earthquake resilient construction of critical facility buildings; additional provision for health facility; firefighting facilities at the building level; planning for self-sufficiency reducing dependency on outer support; planning for earthquake disaster management; provision of a helipad in open spaces for helicopter support), preparedness of local people (dissemination of information, awareness raising and capacity building), etc. The findings of this research will guide policymakers to understand importance of integrating risk sensitivity of landuse plan and thereby take necessary for this purpose to increase earthquake resilience. This methodology is applicable to other hazards, and other areas of Bangladesh as well as other countries. In future, researches should be carried out to assess risk sensitivity of landuse considering detailed and multiple hazard assessments.