Wave overtopping erosion tests at Groningen sea dyke

Abstract

In the present report field erosion tests of the inner slope of a sea dyke in the province of Groningen (near Delfzijl) are described for the situation of severe wave overtopping. Three types of tests have been performed: tests at the present grass cover, tests at a reinforced grass cover and tests at a section of bare clay. At the reinforced grass cover section a provisional Smart Grass Reinforcement (SGR) system was installed in May 2006 (Royal Haskoning & Infram, 2005). The test sections were 4 m wide and extended over about 16 m along the inner slope, down from the dyke crest. It should be remarked that the erosion tests focused on the inner slope from the crest to some distance above the level of the service road. Below the service road, the berm slope was artificially strengthened with riprap as to avoid any damage on beforehand. The tests have been carried out under the framework of ComCoast, Work Package 3 (WP3). Additional measurements have been commissioned by the SBW program (Sterkte & Belastingen Waterkeringen or in English: Strength & Loads Water Defences), a research program for improvement of knowledge of present defences. These measurements included: measurement of flow velocities and water depths, infiltration tests, determination of the soil shear strength and an additional erosion test at a bare clay section. The present report is an overall report, presenting a full overview of all test activities, as far as conducted under the responsibility of the consortium. At a later stage, the SBW measurements will be analysed further within the scope of the SBW program. Where applicable, however, some preliminary results are included in this report. For further information, the present report addresses background reports that were written within the framework of ComCoast or SBW. Special reference is made here to the report on the wave overtopping simulator (Infram & Royal Haskoning, 2007), a summary of which has been presented in the present report in Chapter 4.Civil Engineering and Geoscience