Considerations on geomorphological maps for territorial planning in the Modena Apennines (Northern Italy)

This contribution shows, through some examples,that the current instability processes sometimes do not completelycorrespond (concerning presence, location, state ofactivity and/or extent) with those mapped by PTCP HydrogeologicalHazard Maps, which is the document used by theProvince Administration for its territorial planning.The differences highlighted are due to different causes.One of them is the fact that the PTCP Hydrogeological HazardMaps are practically derived from the Regional Geologicalmaps in which superficial deposits have secondary importance,while bedrock and structural-tectonic aspects aregiven the highest relevance. Another cause is represented bythe very active and intense geomorphological dynamics ofthe Apennines which may produce or reactivate instabilityconditions.An important aspect to underline is that the PTCP HydrogeologicalHazard Maps identify areas with planning constraints,which have effects at a municipal scale; it does soby starting from a cartographical basis whose primary aim isnot the definition of instability processes and whose updatingis not homogeneous.Taking into account this aspect, the PTCP HydrogeologicalHazard Maps should be updated not only on the base oftraditional geological mapping, but also following the criteriaof detailed geomorphological mapping which can preciselydefine the genesis, dynamics and morphometry of instabilityphenomena.An important consideration, in relation to territorial planning,is that the PTCP Hydrogeological Hazard Maps shouldbe used just as a “base document”, which requires morenecessary detailed deepening at the municipal scale, accomplishedthrough accurate geomorphological mapping, at leastfor the areas that are going to be urbanized.The geomorphological mapping should also update thoseelements of the landscape which could have changed fromthe official topographic base map.Detailed geomorphological mapping, possibly undertakenwith the methodology proposed in this paper, could be givenin charge also to professional geologists in accordance withstandard procedures set in collaboration with the ProvincialAdministration.