Talk:Hard shoreline protection structures

Review by Greg Rozynski

General remarks

This short entry provides a convenient entrance to a vast topic of coastal protection measures with traditional methods. Therefore, it is a very useful contribution, because most readers begin their search for knowledge on (traditional) coastal protection by typing a phrase like the title one. Once entered it guides the readers to more specific topics of their interests. Being a gateway to more detailed description of particular solutions it is both sufficiently succinct and precise.

Amendments

Lee-side erosion

Some criticism can be raised as to the slightly imbalanced treatment of lee-side erosion in the description of groin fields or shore parallel structures. One has an impression that the lee-side erosion is an inherent and unavoidable misfortune, so this type of structures had better be always avoided. In the reviewer’s opinion more balanced message can be delivered when a comment how the lee-side erosion can be reduced or mitigated is added. This can be achieved by the following sentences, inserted after the sentence ‘While protecting the coast…the area of interest.’ : ‘The lee-side erosion effect can be reduced/mitigated when several terminating groins are built as sediment permeable structures or when they have reduced lengths; the rates of permeability of these terminal groins or their reduced lengths should be determined by numerical modeling. In some cases sudden change of coastal orientation may reduce the lee side erosion to an acceptable level.’

Seawalls and revetments

The second amendment concerns the description of adverse effects of seawalls and revetments. Before the concluding sentence: ‘For more information on this topic…’ it is worth adding the following sentence: ‘Negative consequences of seawalls or revetments can often be mitigated by regular artificial nourishment of the eroding beach in front of the hard structure.’

Review by Barbara Zanuttigh

General remark

This introduction meets the goal to guide the reader towards more detailed contribution on traditional defence schemes.

Comments and suggested improvements

A couple of pictures showing typical applications of type a) groynes and breakwaters and type b) seawalls and revetments would be helpful for the less expert reader. The way floating breakwaters are introduced is not completely correct: “An alternative structure for fixed breakwaters”. Usually floating breakwaters are efficient in a limited range of incoming wave periods and milder climates. Two points regarding seawalls and revetments that so far are presented in a completely negative way (I agree with the first reviewer): a) one may not wish to interfere with sediment transport processes but may wish to limit wave run-up and overtopping during storms to reduce inland flooding; b) the processes induced by these structures (essentially wave reflection) leading to worse performance as far as bottom erosion is concerned should be at least mentioned.