One of the negative effects of hard, grey infrastructure, as you said, is increased current speed and less friction than in the case of infrastructure that includes vegetation. This type of infrastructure makes it possible to develop habitats and to retain sediments in order to create ecosystems, such as wetlands, which are conducive to fish habitat. Green infrastructure has shown that it offers many benefits.
In some cases, impermeable infrastructure, such as walls, increase the energy of waves, which is a much more perverse effect for the environment and is even more pronounced where a sawtooth surface is involved.
Various types of infrastructure have been built at various times and this type of infrastructure obviously has more harmful consequences.