J. R. Díaz de Terán

Geoscientific maps for planning in semi-arid regions: Valencia and Gran Canaria, Spain

Abstract Two case studies of the application of geoscientific maps for planning in semi-arid regions are presented, one for the Mediterranean province of Valencia and another for the island of Gran Canaria (Canaries). Both regions are very dynamic from the point of view of population growth and urban-touristic-industrial development, and they suffer from a serious degree of environmental degradation. The provincial/ island governments have undertaken programmes of geoscientific mapping and assessment to serve as a basis for the establishment of guidelines for future planning. Two map sets have been made (1:200,000 in Valencia and 1:50,000 in Gran Canaria), based on initial maps of homogeneous integrated units. These represent a series of hierarchical land subdivisions, progressively smaller and more detailed (morphodynamic environments, systems, units, elements), defined on the basis of morphostructure, climate, lithology, surficial deposits, landforms, topography, active processes, soils, vegetation and human influence. Each individual map unit is described by means of a form which includes 114 items, summarising its environmental features. Morphodynamic units have been evaluated in terms of qualities significant for planning, and a series of derivative maps has been developed (geologic hazards, soil capability, present degree of erosion, potential erodibility, quality for conservation). A final map shows the most advisable types of uses and the main limitations for human activities, mainly due to engineering geological factors. This is a synthesis document which can be used directly by planners.

Environmental-economic evaluation of the filling and reclamation process in the bay of Santander, Spain

The historical development of a process of reclamation of intertidal areas in an estuary has been quantitatively studied by means of old engravings, maps, navagation charts, and aerial photographs. These show that about 83 percent of the natural coastline of the estuary has disappeared, nearly two-thirds of its intertidal area has been covered, and over 40 percent of its volume has been lost. The rate of this artificial process is several tens of times faster than that of the natural sedimentation. Extrapolation of the observed trends shows that, if these continue, the intertidal areas would disappear completely in 31 to 105 years.Theoretical calculations based on comparisons with other estuaries show that the accumulated loss in the productivity of living matter (in the form of primary producers), since the process started about 140 years ago, could reach 1.5·1010 kg. This could represent, considering several possible food chains, the equivalent of the food necessary to sustain several thousand people for life.An economic analysis of the impact of the process has been made by considering, first, the decrease in fish and shellfish catches in the bay (using historical data and data about present clam productivity) and the decrease in its aesthetic quality and recreational potential. These were determined by means of interviews with the population to obtain a “demand curve” for the willingness to pay for the preservation and use of the bay. Second, the price of the man-made land obtained was considered. The data obtained show that the economic losses would offset the benefits within 10 to 30 years.

A technique for the definition of environmental geologic units and for evaluating their environmental value

Abstract This paper describes the criteria used to define environmental geologic units in the coastal zone of Santander, Northern Spain, and the technique applied to estimate their environmental value. The work reported is part of an integrated environmental study of the area. Environmental geologic units have been defined using two main criteria, morphology and lithology. Two separate maps were produced and then combined to obtain an environmental geologic map, in which each unit has uniform morphological and lithological features. A series of parameters were chosen as indicators of the resource value and the limitations for use by man of the different units. Each parameter was graded independently, for all units, in a relative scale and then added up for each unit to obtain a measure of its environmental value from the geological point of view. This value was corrected by multiplying the parameters by appropriate weighting and singularity coefficients. The figures obtained were standardised by means of cumulative frequency curves for the different distributions of values and five classes of “environmental geologic value” were obtained. The distributions of classes obtained are presented in maps which reflect the potential for use by man of different zones in the area of study. The different alternatives considered are compared and discussed.

Open image in new windowThe Application of ERT for the Geometrical Analysis of the Sebrango Landslide, (Cantabrian Range, Spain)

Electrical resistivity tomography (ERT) was applied to the geometrical characterization of the Sebrango Landslide reactivation (Cantabrian Range, Spain), which threatened the villages of Sebrango and Los Llanos on June 2013. The Sebrango Landslide is a 1.2 km-long landslide that episodically affects a hillslope located at the northern margin of the Deva River, at the northern sector of the Liebana Syncline. ERT surveying offered the opportunity to investigate the unexposed geometry of the landslide just after finishing the 2013 paroxysmal stage, while other surveying techniques, as core logging, were ruled out for safety and local government regulation during the hazard emergency. The obtained resistivity images provided information on the thickness of the terrain involved by the landslide, on the location of the inner rupture surfaces, and on the groundwater flow pattern within the hillslope. The results suggest that the landslide involves a 40–60 m-thick mass of complex structure. The resistivity images show a profuse groundwater flow within the slid mass, especially in the header area affected by the 2013 reactivation. The images also show a preferential groundwater flow longitudinally to the axis of a secondary landslide lobe, at the eastern sector of the landslide body, pointing to this sector is that actually shows greater deformation, as opposed to the main lobe oriented NW-SE. The landslide geophysical model was constrained by a core logging and monitoring campaign conducted during the subsequent months. From a geomorphological perspective, our results suggest that the particular entrenchment dynamics of the Deva River is playing a key role as a preparatory landslide factor.

Conservation and restoration of endangered coastal areas: The case of small estuaries in Northern Spain

Abstract The extent of degraded estuarine and wetland zones on the north coast of Spain is discussed. A method for the analysis and diagnosis of such zones is proposed. The method is based on the identification and mapping of homogeneous environmental units and the definition of indicators for the assessment of these units in terms of attributes relevant for restoration and management. The specification of a set of criteria enables the diagnosis maps thus obtained to be transformed into maps with proposals for management actions, for which specific designs are proposed. The cost of the actions proposed is also estimated. The results obtained from the analysis in three small estuaries are extrapolated to determine the possible extent of different rehabilitation activities and to estimate the cost of recovery plans for the whole coastal sector analysed.