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Geo-Resources & Geo-Hazards

We know from the study of past societies that some of them failed because they did not recognize the importance of their natural habitat (DIAMOND 2005). Today, the large global population stretches the resilience of the environment to a possible maximum. This is especially true in urban areas, where the majority of the global population is living today (WORLDWATCH 2007) – often with a rather bleak perspective (DAVIS 2006). Therefore, it is very important for a sustainable development to know a city's geo-potentials, i.e. the geo-resources available for the cities subsistence and growth and the geo-hazards threatening its population and infrastructure.

In recent decades, more and more hazardous areas are urbanized, where natural events may turn into catastrophes; e.g. when settlements on unfavourable underground exposed to climate change may be subject to mass movements, or where settlements develop into areas of high seismicity or volcanic activities. FISCHER-KOWALSKI et al. (1997) stresses the fact that cities have a metabolism: they need water, fertile soils and mass resources to sustain their population while simultaneously egesting waste into their environment. To grow and expand, cities need additional material. In many cases, this material is loam and clay for bricks as well as sand, gravel and limestone for concrete. It may be astonishing at first sight only, that sand and gravel were the most extracted resources on our globe in 1996 (cf. WELLMER & BECKER-PLATEN 1999, 2002). On the one hand, cities often seal these resources without knowing and thus have to transport them from far away with high economical and ecological costs. On the other hand, extraction of resources hinders urban land occupation or has negative effects on the environment and settlements in the surrounding. Despite this importance of geo-resources and geo-hazards for urban growth, only a very small proportion of a population is able to read a geological map or to develop an understanding of the underground. This should motivate geoscientists to put in efforts to translate and visualize their knowledge for a sustainable land use planning (cf. HOPPE ET AL. 2006, MARINONI & HOPPE 2006, LAMELAS ET AL. 2007-2010, HOFMANN ET AL. 2009).

Powerful tools to translate the geo-potentials of a certain area into easily understandable information are GeoInformationSystems (GIS), which can be used to translate geo-scientific data into thematic maps that show e.g. groundwater availability and vulnerability, soil fertility, nitrate retention capacity or geothermal potential (e.g. Atlas of Geo-potentials by HOPPE & MITTELBACH 1999, STACKEBRANDT & MANHENKE 2002). This attempt may be strengthened by 3D visualisation, e.g. using the software gOcad (cf. http://www.pdgm.com/products/gocad.aspx and MALLET 2002), which allows for instance a more detailed calculation of typical groundwater vulnerability estimation (cf. LERCH & HOPPE 2007, LAMELAS ET AL. 2007).

A typical workflow to give recommendations for future land use – for example in the surroundings of a city in a fluvial plain – could be the following: First, all relevant geo-scientific information has to be compiled, aggregated and brought into GeoInformationSystems (e.g. ArcGIS and gOcad) to reconstruct the basin´s history and its structural and sedimentary architecture. Then, a model for defining natural resources and hazards has to be developed using filters or other established methods (e.g. grain size distribution to determine areas providing sand and gravel). This information is then documented in an atlas of geo-potentials which consists of a collection of easily understandable thematic maps showing all relevant geo-hazards and geo-resources needed for regional land use planning.

However, as other aspects such as economic and ecologic factors usually play an important role in decision processes, Spatial Decision Support Systems (SDSS) on the basis of e.g. Analytic Hierarchy Process (AHP) or the Preference Ranking Method for Enrichment Evaluations (PROMETHEE; cf. SAATY 1977) are needed to allow a participatory approach of all groups interested in land use. Since such systems are not always available within standard GIS platforms, additional software extensions are required (MARINONI 2004, 2005). SDSS facilitate the evaluation of various regionalized criteria (e.g. from the atlas of geo-potentials) by means of integrated multi-criteria evaluation methodologies, where every stakeholder can enter his/her own weights for the criteria influencing the project. This means, he/she can rate how important the different factors ( e.g. protection of groundwater, thickness of sand and gravel, overburden on sand and gravel, quality of soil, distance of mining area to settlement, protection of flora and fauna habitat etc.) seem to him/her for the decision of a specific project. The resulting maps then show both best suitable sites and areas of conflict of all stakeholders. Thus, by creating maps showing the spatial consequences of the priorities set by different stakeholders, SDSS can help to concentrate debates about land use planning to knowledge based discourse instead of ideological arguments (e.g. use of raw material versus nature conservation; cf. HOPPE ET AL. 2006, MARINONI & HOPPE 2006, LAMELAS et al. 2010).

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