It is a interesting research, the hydroelasticity of the ship attracts a lot of researchers, whether the boat is made by steel or other material. My suggestion is, you can perform your research, and the result will tell you whtther or not the hydroelasticity is needed. If you can prove it is not needed, that is also a good result.
As in my understanding during working on the ship design problems the hydro-elastic effect consider for the design and its no doubt their are lots of researchers working on the ship design so i would you like to suggest you to select an appropriate material and perform your research with considering this phenomena and compare it with available published results in which this effect not consider and final you ill come with an exact conclusion.
It is a very interesting subject. Hydro-elasticity is a very important factor in designing of ships and marine vehicles. Investigation of this phenomena in river, in my mind, is a novel study and can be considered as an initial point in this field. I am sure it is a valuable research because you are going to study Hydro-elasticity due to pressure in a shallow water, or a canal for doing your research. But note that, since in a river, there is not any surface wave, the heave motion of a marine vehicle, expected to be negligible, therefore, slamming phenomena do not need to be studied, and I propose you to study hydro-elasticity of ship due to flow, and effects of sided walls and bottom of river on pressure. Deformations of propeller in the river environment is also a very interesting subject. If you publish a paper, let me know, because this subject is really alluring for me.
For answer this question, firstly we should know when Hydroelasticity is important. Hydroelasticity means that the fluid flow and the structural elastic reaction are considered simulaneously and that we have mutual interaction, that is,
1-The elastic vibrations cause a fluid flow with a pressure field
2-The hydrodynamic loading affects the structural elastic vibration
For study phenomenas due to Hydroelasticity, there is ways and criteria ,for example , Wagner and von Karman methods for slamming, drop test for Green water, comparison with standards (for example, DNV classification society for determine pressure loads due to Hydroelasticity in plate).
As example, for bottom slamming the Ochi (1964 ) criteria has offered. For more information, I think one of the best and classical reference is:
Hydroelasticity of ships , by Bishop and Price (1979)
In my opinion, the hydroelasticity effects do not only affect the strength of the ship structure but also the seakeeping. If you use the flexible or inflatable boat, the deformation caused by hydrostatic pressure and fluid flow, in shallow water, will influence the magnitude of resistance and ship motion.