Multidisciplinary approach for urban planning in alluvial karstic zones: Case study from the Central Ebro Basin (Spain)

Constructive design on inhomogeneous ground often faces geotechnical problems, particularly under ongoing karst processes, namely subsidence or collapses. Careful analysis of this kind of problems by means of different techniques, together with accurate geological models, is needed for correct urban planning. In this work the main results obtained during an urban planning study in the proximities of Zaragoza city (NE Spain) are presented. Several independent approaches give results that can only be clearly interpreted when integrated as a whole. The first approach is related to historical–geomorphological analysis from maps and series of aerial photographs. The second approach is an intensive geophysical survey (GPR, magnetometry, gravimetry, EM). The third approach includes the analysis of subsoil characteristics by means of trenches, boreholes and dynamic penetration tests. Prior studies failed in the correct characterization of this area, mainly because of the difficulties in interpreting the obtained data. The discussion of this work analyzes the sensitivity of techniques and reliability of the obtained results, and the importance of correctly defining the geological-geotechnical model. The presented methodology responds to the main potential problems to be analyzed in complex alluvial environments linked to karst activity and can be applied in similar contexts where different approaches must be integrated to obtain realistic geological models.