V. Rivas

Land management versus natural factors in land instability: some examples in northern Spain.

The objective of this work is to test a hypothesis formulated on the basis of former results which considers that there might be a “global geomorphic change,” due to activities related to land management and not determined by climate change, which could be causing an acceleration of geomorphic processes. Possible relationships between some geomorphic processes related to land instability (landslides or sediment generation) and potential triggering factors are analyzed in study areas in northern Spain. The analysis is based on landslide inventories covering different periods, as well as the determination of sedimentation rates. Temporal landslide and sedimentation rate trends are compared with different indicators of human activities (land-use change, logging, forest fires) and with potential natural triggers (rainfall, seismicity). The possible influence of the road network in the distribution of landslides is also analyzed. Results obtained show that there is a general increase of both landslide and sedimentation rates with time that cannot be explained satisfactorily by observed rainfall trends and even less by seismicity. Land-use change appears to be by far the main factor leading to land instability, with some changes producing up to a 12-fold increase of landslide rate. A relationship between road network and the spatial distribution of landslides has also been observed. These results do confirm the existence of an acceleration of geomorphic processes in the region, and also suggest that climate-related factors play a limited role in the changes observed.

An approach to environmental assessment within the land‐use planning process: Northern Spanish experiences

Abstract The problems involved in environmental assessment of land‐use plans are discussed. A methodology is proposed for incorporating into the assessment of a plan the modifications that the physical environment would experience as a result of the plans implementation. Thus, EIA can be integrated into the planning process. Impact assessment and comparison between alternative plans can be made using quantitative and qualitative indicators, some of which are proposed. Several case studies in northern Spain are used as the basis for the suggestions made.

Perception of indicators of coastal environment quality by municipal officials in northern Spain

This paper analyses the degree of scientific information used by coastal municipalities in Cantabria, Spain. It also analyses the opinions of municipal officials on selected indicators of environmental quality in this coastal area and compares them with the opinions of a group of scientists. A survey was made of the view of local public officials and environmental scientists at the University of Cantabria. It was found that officials rate a developed coast of higher quality than scientists and rarely use scientific information in decisions affecting the coastal environment. The need to develop a list of indicators with clearly defined methods of measurement is pointed out.

Landslide Hazard Scenarios Based on Both Past Landslides and Precipitation

The goal of this contribution is to develop a set of methods and techniques for modelling landslide hazard, in order to obtain better predictions and, therefore, to reduce the risk associated to this type of process. The research has been carried out in North-Western Guipuzcoa (Spain), an area intensely affected by shallow landslides. Hazard predictions must be based on several assumptions, termed scenarios. To propose more realistic hazard scenarios, two different approaches have been applied: on one hand, by extrapolating the trends observed from recent past landslide activity and, on the other hand and indirectly, from the empirical analyses between landslides and their main trigger (precipitation). It was necessary to get long time series of landslide occurrences, through which sound future frequency could be estimated and relationships between landslides and their predisposing factors established. The landslide inventory includes 20 time intervals ranging from the 50s of last century to the present and has been obtained by analyzing photographic images from different dates. Rainfall records of several weather stations have been analyzed, establishing correlations between landslides and precipitation intensity-duration. According to rainfall quantity, duration and intensity, as well as landslide activity, six multiple occurrence regional landslide events (MORLE), regarding rainfall extreme events, have been identified and characterized. On the basis of both types of scenarios quantitative hazard models could be obtained.

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.