Print Email Facebook Twitter Measuring Programme Amelander Zeegat Storm Season 2003-2004: Measurement report on two northwesterly storms Title Measuring Programme Amelander Zeegat Storm Season 2003-2004: Measurement report on two northwesterly storms Author Hordijk, D. Corporate name Rijkswaterstaat Date 2004-10-01 Abstract Primary water defences protect the Netherlands against flooding by the North Sea, the major rivers and inland seas Markermeer and IJsselmeer. The Dutch Water Defence Act [Wet op de Waterkering] stipulates that these water defences have to be tested every five years to determine if they guarantee the statutory safety level with respect to the applicable Hydraulic Boundary Conditions, which lay down normative water levels and waves. Wave measurements are carried out at various stations off the straight Dutch coastline near Petten and off Zeeland estuaries West Scheldt and East Scheldt, but as yet there are no relevant nearshore data available of the Wadden Sea. There are signs that waves penetrating from the North Sea via tidal inlet Amelander Zeegat (see figure 1.1) into the Wadden Sea, strongly affect the local wave pattern in the Wadden Sea if water levels are high, e.g. in the case of a storm surge. Measurements in a tidal inlet system during storms are therefore essential for understanding wave propagation into the Wadden Sea and for testing the reliability of present wave modelling. To this purpose, a measuring programme with directional waveriders was started at Amelander Zeegat at the end of 2003. The objective of the measuring programme in tidal inlet Amelander Zeegat is to monitor wave propagation from the relatively deep North Sea via the tidal inlet into the Wadden Sea during storm conditions. The programme concentrates on penetration of long, northwesterly waves with periods of approx. 10 to 15 seconds, which can severely affect wave run-up and overtopping when penetrating up to the water defences along the Wadden Sea. During storm season 2003-2004, two storm periods occurred which caused a significant increase in Wadden Sea water levels. On the basis of the data, the conclusion can be drawn that the degree of North Sea wave penetration into Amelander Zeegat strongly depends on the concurrent water levels. A comparison of the wave spectra measured during the storms, shows that the energy in the left part of the spectrum, i.e. < 0.25 hertz, virtually completely dissipates at the shallow outer delta when water levels are low. A comparison of the spectra measured at high tides with considerably increased water levels, demonstrates that also in the case of increased water levels much of the low frequency energy dissipates at the shallow outer delta. When water levels are this high, part of the low frequency energy does penetrate into the tidal inlet, which results in clear spectral peaks at approx. 0.1 hertz at the first two stations at the Wadden Sea side of the outer delta. This low frequency energy has completely disappeared, however, in the spectra of the stations location at the flood basis. The hypothesis is that the North Sea waves penetrating into the tidal inlet, refract towards the channel walls during penetration through the channel, after which they dissipate on the channel edges and on the shallower areas behind them. Subject measurementsAmelandZeegatstormwavewave patternmeasurement programme Classification TLJ800700TPG132120 To reference this document use: http://resolver.tudelft.nl/uuid:43a1b0ef-bbb6-45e7-b5ab-697ad28b4316 Publisher Rijkswaterstaat, RIKZ Source Werkdocument: OS/2004.129w Part of collection Hydraulic Engineering Reports Document type report Rights (c) 2004 Rijkswaterstaat Files PDF rikzOS2004129w-16dec2005.pdf 595.7 KB Close viewer /islandora/object/uuid:43a1b0ef-bbb6-45e7-b5ab-697ad28b4316/datastream/OBJ/view