Karst Constraint Perimeter

Description

Areas of constraints defined according to the nature, importance, evolutionary character, density of karst phenomena and topography. Descriptive summary Karst constraints perimeters correspond to areas where a natural risk or a major geotechnical constraint for urbanisation (constructible, urbanisable, construction of large infrastructures and transport of fluids and energy) is present. The administrative permit authority may then require the applicant to carry out studies and take measures to ensure the integrity of the project and the safety of its occupants. In addition to the 50m zone defined by the cartographic symbol representing the karst phenomenon, two types of stress zones have been defined: • areas of high stress correspond to areas where any construction must be avoided or even prohibited, because the risks associated with karst are significant. They have been defined when the presence of several karst phenomena very close to each other justified the coalescence of their areas of constraint (the fields of sinkholes, ...), when the formation of new karst phenomena is very likely (a dry valley under which withdrawal and dissolution related to the circulation of groundwater can induce collapses, ...), when the karst phenomena are active or reactivated and that one can predict the way in which they are likely to evolve (the natural tendency to recoil the chantoirs upstream, up to the limit between the limestones and the impermeable rock, the "rejeu" and the deepening of certain sinkholes, ...) or when a cavity presents risks of collapse of the roof, etc.; • areas of moderate stress are areas where lower risks than those in areas of high stress are estimated. The size, density and activity of karst phenomena are lower. Such zones have also been defined around areas of strong constraint in order to constitute a security perimeter (precautionary principle). Applications for permits must not be systematically refused, but must be the subject of additional investigations (geotechnical and geophysical studies, etc.) in order to verify and guarantee the stability of the soil and foundations. In the particular case of Tournaisis, collapses are most often related to groundwater pumping. The combined analysis of collapse density and limestone dewatering provides a good spatial and temporal indicator of the risk of collapse. Three areas of constraint have been defined: • an area of high stress where the density of collapses is greater than 15 units/km2; • an area of moderate stress where the density of collapses is between 1 and 15 units/km2, or where the dewatering of the limestone basement is greater than 10 m; • a low stress zone where the density of collapses is less than 1 units/km2, or where the dewatering is more than 5 m. This zone has no equivalent in the rest of Wallonia and was introduced to take into account the approximation of the different models and the evolutionary character of the piezometric surface. Implementation framework at spatial planning level Karst constraints are linked to the concept of natural risk or major geotechnical constraint for urbanisation within the meaning of the former CWATUPE (Wallon Code of Spatial Planning, Urbanism, Heritage and Energy) and now the CoDT (Code of Territorial Development). Article D.IV.57 of the CoDT is an opportunity for the administrative authority managing permit applications to impose standards on the stability, integrity and safety of immovable property following its possible state of disrepair in the event of a disaster associated with a particular risk or geotechnical constraint. The last perimeters of karst constraints were stopped in 2006. The Karst Atlas (see other data series related to the environment) is one of the technical supports (like geological maps, for example) for these karst constraints for urbanisation. This Karst Atlas constitutes a form of environmental constraint in terms of the protection of nature and / or the natural resources of the subsoil following the permanent, partial or temporary occupation of any karst phenomenon accessible by any species protected by the LCN (Nature Conservation Act) and the Natura 2000 directives; protection of groundwater (Water Code), protection of the geological, archaeological or even historical or geomorphological heritage within the meaning of the Heritage Code (listed sites), etc. The Karst Atlas does not therefore systematically constitute a form of major constraint on urbanisation within the meaning of the CoDT. It has been suggested to the authorities...

Resources

Name Format Description Link
23 https://geoservices.wallonie.be/arcgis/rest/services/AMENAGEMENT_TERRITOIRE/CONTR_KARST/MapServer
0 https://geoservices.wallonie.be/inspire/atom/NZ_Service.xml
0 https://geoservices.wallonie.be/geoserver/inspire_nz/ows?service=WMS&version=1.3.0&request=GetCapabilities
61 https://geodata.wallonie.be/dataset/115d71f6-2670-4628-a3a6-eea71e3279b4
0 https://geoservices.wallonie.be/arcgis/services/AMENAGEMENT_TERRITOIRE/CONTR_KARST/MapServer/WMSServer?request=GetCapabilities&service=WMS

Tags

  • source-d'accident
  • catastrophes,-accidents,-risques
  • zones-à-risque-naturel
  • régional
  • codt
  • territoire
  • géographie
  • karst
  • règlement
  • urbanisme
  • aménagmeent
  • législation

Topics

  • ENVI
  • SOCI
  • TECH

Categories