A description of structural coastal protection is considerably more 
valuable if morphological data regarding coastal changes above and below 
sea level, sea stages, storm tides, wind observations and other information 
are added. Such descriptions are of greater value if based on data and 
measurements, measurements in nature as well as on models, systematically 
arranged, carried out, and presented with a view to the entire regional 
development. 
A positive contribution to the knowledge of the functions and effect- 
iveness of groins can be made only after a long period of observation. The 
unexpected malfunctions of groin systems sometimes are concealed to avoid 
adverse publicity and to protect the designer. However, we can learn from 
failures, and the sooner they are made known the sooner they can be elimi- 
nated by structural changes. The survey of available German publications 
on groins indicates that great attention was given to coastal morphology 
as the structures were analyzed. 
In general, considerable effort was made to achieve close cooperation 
between the engineers and natural scientists. 
III - CHRONOLOGIC SURVEY OF GERMAN DOCUMENTATION ON GROINS 
Contributions to the knowledge of groin construction (starting in 
1818) which were based on significant events in the German coastal zone 
and led to their use and development, are discussed in this part of the 
review by Dr. Petersen. The chronologic progress of German groin con- 
struction with regard to distinct scientific, engineering and economic 
trends is surveyed in five steps. 
a. Construction period prior to 1900 - By 1900 several basic 
Papers on coastal morphology, coastal engineering and a treatise on the big 
Baltic Sea storm tide of 1872 were already published in which the authors 
tried to find the causes and effects of coastal changes. They were good 
observers of natural phenomena on beaches. The groins constructed during 
this period have a special experimental value, and for this reason re- 
searchers in subsequent years draw often on the ideas of older authors. 
They compare the old construction methods with the observations of a later 
period to see how the older design ideas materialized relative to their 
effectiveness. 
b. Construction Period 1900 to 1920 - In this period a distinc- 
tion between sea groins and stream or river groins can be noted. However, 
full definition relative to functional limitation and structural forms 
involved is not made clear. 
c. Construction Period 1920 to 1930 - The German Harbor Engin- 
eering Society entered into the discussion on questions dealing with groin 
construction. Of great significance to the German coastal problems was 
4\ 
