This chapter gives wave statistics along the Medlterranean Coast of Egypt This information can be used to estimate longshore transportation of sand from the direction of propagation and the energy flux of waves at the break point (ref 1) In addition, the divergence of the longshore transport rate identifies areas of potential erosion/accretion, while the magnitude of the divergence is proportional to the rate of erosion/accretion (refs 2–4).

Reliable data on wave climate prior to this study are not available for the Nile Delta littoral cell. Some wave data are presented in refs 5–7, but do not provide adequate wave direction Inman et al (ref 7) give tables of wave climate based on shipboard observations, but this type of data is notably inaccurate In order to obtain an accurate description of wave climate along the coast of Egypt, two stations for the measurement of wave energy and direction were installed off the Nile Delta at Abu Quir and Ras El-Bar (Fig. 1). Each station consists of four basic units plus cables for interconnections: the recorder unit, acquisition unit, power unit, and sensor array. The sensor arrays of the two stations incorporate three wave pressure sensors The system is developed and produced by the Center for Coastal Studies, Scripps Institution of Oceanography and is called cassette acquisition system (CAS). This system is well described by Boyd and Lowe (ref. 8).

The pressure sensors at Abu Quir Station are at about 18 km from the shoreline, mounted 6 m below mean water level (MWL) and 12 m above the sea bed. At Ras El-Bar the sensors are at 6.5 m below MWL and 0 6 m above the bottom, approximately 900 m offshore of the shoreline. The sensors are positioned linearly parallel to the Coast. At these two stations, data are recorded for 34 minutes, once every 6 hours, so that there are 4 wave records per day at each station. Figure 2 gives the configurations of the Abu Quir and Ras El-Bar wave arrays.

The measured data have been subjected to statistical and spectral analysis. For each 34-minute data set, the total variance (¿12) of the sea surface displacement ¿ is obtained The significant wave height Hs' the wave period Tp corresponding to the reciprocal of the frequency of the band with maximum energy density, and a mean direction A, for peak frequency are computed.

ANALYSIS OF WAVE DATA

The three pressure time-series were subjected to preprocessing treatment designed to detect areas of invalid data, based on expected maximum and minimum recorded values for each time series maximum excursion from the mean and expected slew rates. Once the magnitude and slew rate checks have been applied, a linear or quadratic interpolation is applied across the set of spurious values detected The processed time-series resulting from the above treatment is used as input for analysis programs.

Fig. 1 Location of Abu Quir (1) and Ras El-Bar (2) wave Arrays (available in full paper)

Fig. 2 Arrangement of Abu Quir (left) and Ras El-Bar (right) wave arrays(available in full paper)

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