Searching for useful non-systematic tree-ring data sources for flood hazard analysis using GIS tools

Tree-ring analysis has been demonstrated to be a useful tool for palaeohydrology. Selecting suitable study areas is the first step in palaeoflood research using tree-ring techniques. Objective methods are needed to facilitate exploration and subsequent location of basins where sediment-laden flash floods are likely and that also have tree species suitable for dendrogeomorphological research in a palaeohydrological context.This paper presents a novel methodology for selecting preliminary suitable watersheds for dendrogeomorphological palaeoflood research in central Spain. Geographical information systems (GIS) provide decision-makers with a powerful set of tools for the manipulation and analysis of spatial information. Using GIS tools and basic thematic maps, we defined three different indexes concerning the occurrence of dendrogeomorphological evidence. A Consensus Decision Making procedure (CDM) was carried out in order to weight each factor individually prior to combining the factors. As a result, we obtained information about the most appropriate watersheds for palaeoflood research using tree-ring analysis. A total of 189 watersheds appeared to be highly interesting for tree-ring studies. Of these only 17 have flow gauges, so data concerning frequency and magnitude of floods in basins without gauges could potentially be provided by dendrogeomorphological studies. In order locate such sites and to carry out such studies more efficiently, a more objective methodology for selecting watersheds for tree-ring studies is presented.

► Tree-rings have proven a useful tool for flood risk assessment.
► The use of this technique is subject to the choice of the study area.
► So far this step methodology was based on prior knowledge of potential areas.
► Our proposal provides an objective methodology based on GIS to locate potential areas to flood studies with tree ring data.