How to determine the PERIOD of dredging?
May I lay emphasis on the word PERIOD.
The whole question can be interpreted as a "double-meaning" one.
Most likely it was here meant to be the REPETITION of dredging works at one / same location in let say a one year period.
"Wave period" is also the "Cycle" of the wave movement.
Every so many seconds you see the crest height again. (Wave period).
Then: Here it is solely related to maintenance dredging (and not reclamation or capital).
Maintenance dredging (keep ports, channels and fairways at required depths) are subjected to SILTATION, and that is the crux.
This can be monitored (on site) and can be referred to in track-records from the past.
Keep in mind that the port may have been modernized or changed in design.
Then the finances and thus the budget for planning (and for dredging).
Funding by / through local, State, Federal, or in the USA, by other bodies (USACE).
The second interpretation of PERIOD:
If we look at the project itself, in operation, underway, doing at the moment.
Then PERIOD is the time lapse to complete the whole project back to the Client.
And time-lapse is not to be chosen by the Contractor.
It is in the Tender Document. And to adhere to the conditions, yes, you had to look at the capacity of the craft. With TSHD of course the hopper capacity, but even so important the speed of the vessel (as said, where to sail to for "dumping"

.
With CSD (Cutter Suction Dredger (more for capital dredging, but still as well maintenance!) it will be the power of the cutter-head.
And at last the skill of the crew!
Once you are awarded the project, you just have to fulfill the deadline to deliver.
Costs, that is what should have been done already at the very beginning.
Material to be dredged, indeed, very important, but this is not so much for the actual meaning of PERIOD.
Best greetings,
known100