Geo-Environmental Assessment for Determining Suitability of Buildable Land in Context of a Hill Town
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Geo-environmental Assessment for Determining Suitability of Buildable Land in Context of a Hill Town Pushplata* and R. Anbalagan* Abstract Inappropriateness of the building and construction activities tai<ing place in preferred locations in the lower Himalayan region is a cause of concern on account of environmental degradation that is often witnessed along with increased construction activity in most of the popular hill towns of north India. Considerations of stability of hill slopes- considered to be the most important for any development by technical experts are often superseded by locational considerations of proximity to work centres and community facilities, land values, accessibility and solar exposure, in deciding the preferred locations for development, the type of buildings and their builtform in urban settlements in hills. Therefore, a comprehensive appraisal of areas in and around hill towns is important for determining their suitability for development for ensuring their social acceptability, as well as, sustainability. This paper discusses the methodology for geo-environmental assessment of hill slopes for determining their suitability for building purposes, after discussing the problems and issues related to urban development and construction of buildings and roads, which can then become a basis for planning for future urbanization in hill regions. This methodology is demonstrated in context of Almora- a hill town in Uttarakhand, which is witnessing rapid urban growth. Introduction Problems and Issues of Urban Development in Hill Towns Increased construction activities are natural outcome of urbanization in an area. However, Various problems faced by hill towns are these activities, though at much smaller consequent upon unplanned growth and/or scale and pace than that in plains, have the inappropriate planned efforts in some cases. potential to adversely affect and have already These problems range from those related to affected in some cases the sensitive instability of hill slopes and ecological environmental context in which they are disturbances to those related to accessibility located. Building and construction activity of residential areas from work centers and taking place in most of the popular hill are community facilities, traffic and often considered to be a cause of transportation, infrastructure development environmental degradation. Therefore, a and visual incompatibility of builtforms. In proper understanding of various problems, addition, towns that is centres of tourist their causative factors and issues related to attraction face problems consequent upon rapid urbanization and consequent unplanned/excessive tourism. More instances construction activities is essential for evolving of landslides/subsidence of hill slopes/roads, the methodology for geo-environmental failure/cracks in buildings are observed in assessment for determining suitability of areas with increased construction activities. buildable land. Quantitative and qualitative changes in ‘ Associate Professor, Department of Architecture and Planning •'Professor, Department, of Earth Sciences. Indian Institute of Technology, Roorkee hydrology have also taken place, besides of hill slopes/roads and failures/ cracks in loss of vegetation cover and increased soil buildings. In some cases natural drainage erosion. Micro-climatic changes are also courses are also disturbed leading to further reported in some areas (Anbalagan, 1992); instability. In addition, buildings with greater B.I.S., 1998; Pushplata, 2000; Sinaj. 2007 bulk are built on steeper slopes requiring and Venkatesh, 2007). extensive cutting of slopes/ development of large terraces for functional and economic High land values due to shortage of suitable reasons, which result not only in land for building purposes in proximity to disturbances to slope stability and ecology existing centre of development and low of the areas, but in these buildings looking affordability of the majority of inhabitants in out of place as well. Provision of roads, hill towns has resulted in building of houses parking and other infrastructure required for in areas that are located away from centres these buildings/ uses further aggravates the and/ or building on slopes that are climatically problems. All these not only disturb the slope unsuitable or unstable( with lower land values). stability but also disturb the vegetation cover Expansion of residential areas in far off and natural drainage patterns leading to locations necessitates longer walking environmental problems as shown in Fig.1 distances and time to reach work centers and below. community facilities and inadequate infrastructure on account of its high cost. Thus, it is primarily the lack of proper Whereas, building on relatively unstable understanding of the natural environment and slopes obviously aggravates and sometime their affect on the built environment and its causes problems of instability- resulting in incorporation in planning and design of urban frequent instances of landslides, subsidence settlements that has led to a multitude of Absence/ Inappropriate Unsuitable Location and Building Building Site development planning / landuse pattern B u lk w .r.t design Terracing insensitive Existing Natural Slope to slope Restoration of T Vegetation Drains Gradient gradient soil cover Location of Residential W ork V isual areas centres Incompatibility Cutting o f trees Extensive Terracing / w Cutting of Slopes i Natural factors — Unstable Shaded Far o ff Weak geologic strata Steep terrain T Heavy Rainfall Climatic Discomfort Debris generation 1 L a n d Subsid Building Accessibility Water supply. slid e s ence Sewerage failure Instability Inadequate Infrastructure \f \f \f Microclimatic Loss of Soil Disturbance changes Vegetation Erosion of Natural cover Drainage Environmental Degradation Fig. 1: Inter-relationship between Planning of Built Environment and Various Problems in Hill Towns problems in hill towns as discussed above. identifying main criteria, their sub-criterion In order to address the above problems and and indicators/parameters, and assigning issues of a hill settlement it is essential to them weightages on the basis of literature develop a methodology for determination of review and study of hill towns of the region. suitability of land for development/building purposes. Thereafter, a rating scheme on the lines of Landslide Hazard Evaluation Factor (LHEF) Need for a comprehensive technique for rating scheme has been formulated. Finally site appraisal a suitability index has been worked out. Though techniques of geo-technical The suitability analysis has been done taking assessment like [1] Landslide Hazard into account five major criteria, namely, hill Zonation [2], guidelines for selection and stability, ecological sensitivity, location, development of sites in Hill Areas [3] and micro-climate and aesthetic characteristics. slope analysis are available, their application The sub criteria for hill stability are those is at regional level and site level respectively adopted for landslide hazard zonation, that and do not address the issues at settlement/ is lithology, geologic structure, relative relief, area level. Some methodologies and slope morphometry, landuse and landcover techniques of townscape analysis and and hydro-geological conditions [1]. Likewise, environment appraisal are available, most of the sub criteria of second criteria of ecological which are very descriptive and/or largely sensitivity are water sources, natural drainage subjective statements of townscape and/or pattern, vegetation, topography and soil landscape quality. The townscape analysis erosion. The third criterion of micro-climate concentrates on visual qualities of the locality is constituted of sub criteria of solar access, and the environmental appraisals primarily exposure to winds, rainfall and humidity, concentrate on natural systems in the snowfall and skylight/daylight factors. The environment. Whereas, site planning fourth criterion of location is constituted of techniques are generally used for individual proximity to existing development, buildings/site level and have not been adapted accessibility, infrastructure and quality of at larger scale/used as a basis for preparing place. The indicators/parameters of each of landuse plans and development controls: these have been identified. Thereafter ratings Since broader and more complex have been assigned to different categories in environment, planning and built form issues each of these. The suitability of areas from are involved in a hill town context, none of these criteria is determined after multiplying these techniques are applicable as such. the sum total of ratings of all the sub criteria with the weightages assigned to them. This A comprehensive assessment of hilly methodology has been demonstrated in terrains, taking into consideration the key context of Almora- a hill town in Uttarakhand, concerns of natural and built environment is which is witnessing rapid urban growth. essential, as not only both are interdependent: the physiographic (landform, Almora - the study context topography), ecological, climatic, locational The hill town of Almora, situated at 29° 30' N (socio-functional) and visual contexts in a latitude and 79° 40’E longitude at a height of place are also interdependent. Thus, the 1646m above msl, is the administrative immediate need is to develop assessment headquarter of Almora district in the state of technique that are comprehensive, analytical,