Robert -
The 9th, 10th & 11th holes at Royal Dornoch sit right along the water and are not protected by the ridge of dunesland that guards the heart of the course. In the winter of 2004-05, a seawall of large rocks & boulders (about 5-10 yards wide and at least 400 yards long) was laid to protect the 10th & 11th holes. The seawall has yet to be tested by a really bad storm. Hopefully, it will do the job for many years to come. The 9th hole remains very vulnerable.
A similar seawall was built many years ago up the coast at Golspie, to protect holes #3 thru #7 there. So far, it has protected the course, but there is not much breathing space at high tide, even when the sea is relatively calm.
Looking out 25-50 years, the picture is not encouraging.
DT