Maria Piedad Herrera, Ainoha Hoyos, Josep Ramon Medina


It is common to construct a rock toe berm of three to four rocks wide when concrete armor units are placed in the armor layer. This toe berm is a relevant element, especially in very shallow waters combined with steep sea bottoms, where waves directly attack the toe berm and the lowest part of the armor. Several formulas are available to estimate the damage to rock toe berms. In this paper, these formulas are compared for different design conditions within their range of application. Most of these formulas use the damage parameter Nod. However, there are often situations in which wider toe berms are required for a safe design, and the damage parameter Nod is not recommended. A methodology is thus proposed to design wider toe berms based on the damage to the nominal toe berm of three rocks wide (Nod*), considered as the most shoreward part of the toe berm which effectively supports the armor layer.


mound breakwaters; rock toe berms; nominal toe berm; sacrificial toe berm; steep sea bottom

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Burchart, H.F., and Z. Liu. 1995. Rubble mound breakwater failure modes. Proceedings Final Workshop: Rubble Mound Failure Modes. Sorrento, Italy.

CIRIA/CUR/CETMEF. 2007. The Rock Manual. The Use of Rock in Hydraulic Engineering (2nd edition). CIRIA, London, p.C683.

Ebbens, R.E. 2009. Toe Structures of Rubble Mound Breakwaters. Stability in Depth Limited Conditions. M.Sc. thesis Delft. Delft University of Technology, Delft.

Gerding, E. 1993. Toe Structure Stability of Rubble Mound Breakwaters. M.Sc. thesis Delft and Delft Hydraulics Report H1874. Delft University of Technology, Delft.

Herrera, M.P., J. Molines, and J.R. Medina. 2016. Hydraulic stability of nominal and sacrificial toe berms for mound breakwaters on steep sea bottoms, Coastal Engineering 114, 361-368.

Herrera, M.P. and J.R Medina. 2015. Toe berm design for very shallow waters on steep sea bottoms, Coastal Engineering 103, 67-77.

Muttray, M. 2013. A pragmatic approach to rock toe stability, Coastal Engineering 82, 56–63.

USACE. 1984. Shore Protection Manual. U.S. Army Coastal Engineering Research Center. U.S. Army Engineer Waterways Experiment Station. Vicksburg, Mississippi.

USACE. 2006. Coastal engineering manual. Engineer Manual 1110-2-1100. U.S. Army Corps of Engineers. Washington, D.C. (in 6 volumes).

Van der Meer, J.W., 1998. Geometrical Design of Coastal Structures. In: Pilarczyk, K.W. (Ed.), Seawalls, Dikes and Revetments. Balkema, Rotterdam. 15 pages.

Van Gent, M.R.A. and I.M. Van der Werf. 2013. Rock toe stability of rubble mound breakwaters, Coastal Engineering 83, 166–176.