One of the important results of WG141 was a table showing the recommended dimensions of waterways compared to the width of the boat.
For the Boeotian, the decision-maker willing to understand what he signs, or an engineer faced with a waterway design for the first time, this table is of great interest, yet they lack understanding on how to choose one value rather than the other, and why/how these figures were arrived at.
There are factors of utmost importance, and to be answered before starting to calculate.
First, what is the Design boat, its width, draught, length and vertical “draught”. Most of the rest is based on this design boat. (But to fix the Design boat, you may need to study the waterway, first, see below).
Second, is it a free-flowing river, an impounded river or a canal ? The table to use is different in every case, although the usual reference is the table for canals.
Third, what is the design traffic, calculated in boat/year. Of course the margins of safety are not the same in light or very heavy traffic, but quite often the table is read as if the traffic were 200Mt/year, while it may be less than a million.
Fourth, assuming the waterway is a canal, what is its shape ? Trapezoidal, rectangular, KRT ? For each, the speed obtained by the design boat for the same consumption will be different.
The paper will give insights on how to gauge each factor, leaving intricate details to further, modelling studies
At times, we know the size of the waterway rather than the size of the boat, and we try to understand what will be the largest Design boat which can be accommodated in it. The same rules apply, turned the other way. The rationale for that will be explained.
It may happen that it is only one bottleneck which will limit or size the Design boat, a bridge or a lock; again, we can use the same references, read in a specific way, weighting the impact of the bottleneck in the global voyage.
In this way, it will be easy for the newcomers to fully make use of the WG141 Report, leaving to the full text of the report to provide all details of the calculations, formulas, modelling process, etc.