Deleting terrain cause it to not render but still have collision and still be in hierarchy

this is a big problem when i go into a region where i deleted a terrain before because i seem to be going over invisible things

PS, by deleting i mean calling Destroy on it.

a simple version of what i was doing:

var Terrain = Instantiate(terraina,poistion,transform.rotation);

Destroy(Terrain,25);

You can manually destroy the components before destroying the terrain using the GetComponent (class?).