Finnish to English Other General / Conversation / Greetings / Letters

This is an excerpt from a description of a river habitat modeling project. The sentence below is specifically talking about how features of the river bottom were assessed:

"Kivien iskostuneisuus [määritettiin] kolmiluokkaisella asteikolla (täysin iskostunut (indeksi 3), osittain iskostunut (2) ja täysin irtonaista (1)) ..."

It seems as though "iskostuneisuus" refers to how firmly established the stones are in the riverbed, i.e. how easy/difficult it is to knock them loose.

However, even if I'm right about this, it seems as though there must be a technical term in English that corresponds to "iskostuneisuus" -- what would that term be?

Thanks