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This page was updated on 15th July 2026.

Waves can be generated from more than one direction. When waves from two or more directions meet their respective energies, and direction of travel, merge. This can be viewed from adjacent cliff tops. It is common to see resultant waves peak as they continue their movement to a coastline. This peaking, or water mountain, can be problematic for operators of small open boats, but in light weather it is rarely a hazard.

The other impact on approaching waves is their response to "feeling the bottom". Surfers are well placed to appreciate this natural process. It causes the wave speed to reduce and the wave shape to steepen until it breaks.

Open water wave interactions can be visualised out at sea but a different form of interaction occurs near sea walls and rocky shores. Wave reflection occurs, particularly on vertical or steep faces. This can be seen at harbour walls and sea defence structures. Incoming, incident, waves can meet a sea wall at right angles to its length, sometimes referred to as normal to the wall, or the wave meets the wall at an angle, rather like longshore drift waves. A vertical sea wall will cause the incident wave to be reflected, either straight back to where it came from, or off at an angle. Think of a torch beam hitting a mirror, or a ball hitting the cushion at the edge of a billard table. In a science lab, lasers and mirrors are often employed to set up such experiments.

The major conceptual point to remember here is that reflected waves return to meet further incoming, or incident, waves. Standing on a sea wall enables observers to see peaks spring up on the tops of waves. Such wave events can be filmed or videoed, but how can the energy changes be quantified? For several decades coastal scientists have been using electronic methods to record such events on beaches, but only successfully in light and moderate wave and weather conditions. Attempting to quantify such events in storm conditions leads to destruction of sensitive instruments.

What is happening at the coastline or harbour wall is the Local Wave Climate. It is important to obtain data on wave energy in order to understand the impact of wave events such as the February 2026 breach at Torcross. We know that the bigger the wave the higher the energy reaching the shore. Energy quantification, at millisecond intervals, is the omly way that the cause of the breaches will be fully understood. The several breaches along the Slapton Line are listed in Storm Events.

Data on local wave climate can be significantly different to wave buoy data located several kilometres out to sea.

The breach of February 2026 requires objective analysis before any decision as to the type of repair, or long term sea defence, can be designed. If the analysis demonstrates that the local wave climate, through reflection of incident waves from the steel piling sea wall, indicates that the steel piling is the problem then the government needs to reconsider its decision on rock armour.

In 2005, Louise Vennells of the Western Morning News interviewed Coastal Research on the state of the Slapton Line following the 2001 breaches. The article headlined Expert warns coastal road will not last was published in the regional newspaper on 27 December 2005, page 18. A key phrase in the article stated that a study commissioned by Devon County Council "failed to establish the cause of the erosion". Of course, several more breaches have occurred over the last 20 years. Still, no objective analysis as to the cause of wave destruction has been undertaken. Much talking has ensued, many boulders tipped, but money from public authorities is being thrown at a problem that the bureacracies do not understand.

The same recommendations that appear in these web pages were put to the interview in 2005. The road should be removed, it should be relocated on the Western side of Slapton Ley. The Shingle Ridge should become a pedestrian access area only. By removing reflective structures over the 3.5 km length the Shingle Ridge would return to being a natural dynamic system, and be self protecting. Uninhibited cross-shore processes would prevail. That's what happens at the Chesil Beach Shingle Ridge and Loe Bar in Cornwall.

References to Porlock Pebble Ridge, West Somerset, raise questions of other types of human interference over the last few decades.

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