EAK2002 - Empfehlungen für die Ausführung fon Küstenschutzwerken

The \u82Guidelines and Recommendations for the Design of Coastal Structures (EAK)\u91 published in 1993 (Die Küste, H. 55) have been revised based on today\u92s scientific knowledge, technical development and practical experience of the past years. Major parts of the recommendations have been re-written. Together with the unmodified recommendations, D, E and F they constitute the EAK 2002. Guidelines A - C 2002 elaborate on the external forces on coastal structures such as water levels and storm surges, waves and surf, currents, sediment transport and ice forces as well as design principles for sloped structures with wave run-up and overtopping, vertical breakwaters and pile-supported structures. A newly discussed topic is the 'Statistical Analysis of Extreme Events\u91. Moreover, the chapters on ''Geotechnical Aspects of Sea and Estuary Dikes\u91 and 'Construction Materials for Coastal Structures\u91 have been added. While recommendations for planning, design and construction of \u82Coastal Structures on Marshes and Low-lands\u91 are part of the compendium guidelines \u82G 2002: Sea and Estuary Dikes\u91 are a novel contribution. This chapter elaborates on dike design, quality prerequisites for the core material and the cohesive outer layers, the threshold properties, preparation and utelization of which are being defined

Vegetation change in a man-made salt marsh affected by a reduction in both grazing and drainage

In order to restore natural salt marsh in a 460-ha nature reserve established in man-made salt marsh in the Dollard estuary, The Netherlands, the artificial drainage system was neglected and cattle grazing reduced. Vegetation changes were traced through two vegetation surveys and monitoring of permanent plots over 15 yr after the management had been changed. Exclosure experiments were started to distinguish grazing effects from effects of increased soil waterlogging caused by the neglect of the drainage system. Both vegetation Surveys and permanent plots demonstrated a dichotomy in vegetation succession. The incidence of secondary pioneer vegetation dominated by Salicornia spp. and Suaeda maritima increased from 0 to 20%, whereas the late-successional (Phragmites australis) vegetation from 10 to 15%. Grazing intensity decreased towards the sea. The grazed area contracted landward, which allowed vegetation dominated by tall species to increase seaward. Grazing and increased waterlogging interacted in several ways. The impact of trampling increased. and in the intensively grazed parts soil salinity increased. This can probably be explained by low vegetation cover in spring. Framework Ordination, an indirect-gradient-analysis technique, was used to infer the importance of environmental factors in influencing changes in species composition. Many changes were positively or negatively correlated with soil aeration and soil salinity, whereas elevation was of minor importance, Grazing accounted for only a few changes in species frequency, Changes in permanent plots were greater during the first than during the second half of the study period. In exclosures that were installed halfway through the study period, there was a relatively rapid recovery of previously dominant species that had decreased during the first half of the study period. Species richness per unit area in the reserve increased. At the seaward side of the marsh. the altered management allowed succession to proceed leading to establishment of stands of Phragmites australis. whereas on the landward side. the combination of moderate grazing with neglect of the drainage system appeared an effective measure in maintaining habitats for a wider range of halophytic species

Erosionsfestigkeit von Hellern Verbundbericht

Available from TIB Hannover: F95B1744 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman