What is the durability of composite kayaks?

next season im looking to invest in a all out touring kayak to do a couple of long trips and use at the mive local state lake for fitness use. the question is: on the long trips it will be on the great and/or little miami river which can in certain parts get low enough that you can really plow hard into large rocks that are just below the surface and impossible to see and manuever around. how damaging are these to the composite fibergl, kevlar, and hybrid hulls? the manufacturers advertise durability, but im not so sure. im looking at the current designs nomad gts and solstice gts. thank you for any help you can give me.