Near-bed structures are studied in this paper, in particular submerged rubble mound structures with a relatively low crest such that wave breaking does not have a significant influence. Physical model tests have been performed to study the stability of near-bed structures under wave loading, with or without a current. Based on the new data and an analysis of existing data, several methods to predict the stability of near-bed structures have been analysed. One of these methods was found to be the most appropriate. This method was calibrated to relate the erosion of near-bed structures to a mobility parameter. It was found that for low-to-moderate currents in combination with waves, the waves dominate the stability of the rock material; the stability of the near-bed structures can be predicted without taking the influence of the (following) current into account. The obtained prediction method is simple and accounts for the effects of wave height, wave period, number of waves, stone diameter, rock density and crest elevation. More detailed information can be found in Van Gent and Wallast (2001).

The stability of rock slopes subject to breaking waves over a shallow foreshore is addressed in this paper. Physical model tests have been conducted on a 1:100 foreshore slope with a wide range of wave conditions including single and double peaked spectra and severely breaking wave conditions. The measured damage levels are compared to the Van der Meer design formulae, which were developed for conditions with no breaking on the foreshore. It has been found that the results of the design formulae are sensitive to the choice of input parameters (H1/3 or Hm0 and Tm or Tm-1,0) and that the inclusion of the reduction factor for breaking waves (H2%/Hs) in the design formulae should be applied only with caution, depending on the choice of input parameters. These results apply for the conditions tested and should be verified for other foreshore configurations before a definite recommendation pertaining to the use of the Van der Meer formulae for shallow foreshores can be given.