SPATIAL ANALYSIS OF CHANNEL STEEPNESS IN A TECTONICALLY ACTIVE REGION: PUTNA RIVER CATCHMENT (SOUTH-EASTERN CARPATHIANS)

Alexandru - Ionuţ CRISTEA

ABSTRACT: Landforms in the Putna River catchment are the result of a recent tectonic evolution, starting with Early Pleistocene. The longitudinal profiles of the rivers draining the region are expected to reflect, in terms of channel steepness, the influence of tectonic distortions and were further analyzed using a locally determined steepness index. This was derived from a power law fit between upstream area and local channel gradient, extracted from the study area’s DEM. Because other factors than tectonics can determine high steepness values (e.g. lithology), a spatial analysis have been conducted. This indicated that the rock variability hardly explains the hot spots and the rivers are steeper more likely in two north-south oriented narrow strips near the major front thrusts. In order to identify clusters in data values local indices of spatial autocorrelation (LISA, Getis Ord Gi*) have been used. The results confirm that a probably a tectonically induced signal can be noticed at a medium scale (where rock strength influence fails to explain data clustering), though at higher (local) scale other factors such as lithology and mass wasting processes can have stronger influences.

Keywords: Active tectonics, Channel steepness, Spatial autocorrelation, SE Carpathians

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