Flusskorridore und Auenstrukturen im schweizerischen Mittelland (nördliches Alpenvorland) | River corridors and alluvial structures in Central Switzerland (northern sub-alpine area)
Long-term spatial variation of river channel distribution in this alluvial valley zone is described for two examples by analysing historical maps covering a period of over 300 years. Such a time series enables the identification of the occupied river corridor or «Pendelband». Two river sections in northern Switzerland were chosen, one of the Aare river and one of the Reuss river to analyse the spatial evolution of the river channels over time, as well as alluvial structures. Knowledge of the river corridor as an historical reference give us an important guideline when developing appropriate regional measures for river restoration projects.
Ableitung und Analyse flussmorphologisch relevanter Parameter von historischen Karten
Increasing morphological problems are being encountered with watercourses in central Europe, related to impacts on sediment regime with lack and surplus of material, higher bed shear stresses due to narrowing of river beds, and subsequent river bed degradation. Ecological deficits result from the lack of gravel bars, a missing of dynamic river morphology and a lowering of the groundwater table. Up to now, practical studies have generally used descriptive analyses of historical conditions of rivers and their morphology (e.g. defining the morphology as braiding or meandering). This paper deals with the qualitative and especially the quantitative analysis of parameters derived from historical maps. Parameters such as river bed width, radius, slope and sinuosity are first described in a scaling context and then derived from two historical and the present situation at the river Mur in Austria. It is shown that this approach improves the quality of results based on historical maps and gives first ideas about the solution of morphological problems.
A new genus and species of Thyasiridae (Mollusca, Bivalvia) from deep-water, Beaufort Sea, northern Alaska
Abstract Bivalve mollusk shells were collected in 2350 m depth in the Beaufort Sea, Arctic Ocean off northern Alaska. Initial identification suggested the specimens were a member of the bivalve family Thyasiridae, but no known eastern Pacific or Arctic living or fossil thyasirid resembled these deep-water specimens. Comparisons were made with the type of the genera Maorithyas Fleming, 1950, Spinaxinus Oliver & Holmes, 2006, Axinus Sowerby, 1821, and Parathyasira Iredale, 1930. We determined the Beaufort Sea species represents a new genus, herein described as Wallerconcha. These specimens also represent a new species, herein named Wallerconcha sarae. These new taxa are compared with known modern and fossil genera and species of thyasirds.