Character height issue

Hello:

I'm creating a game that deforms terrain on the fly, and the character should always be over the terrain. Now, there are moments when I raise the terrain too high and I don't want the character to move through the terrain, so I change the position constantly, but that creates motion sickness. Is there a way I can fix this? Here's my code:

       transform.Translate(Vector3.forward * (movementSpeed / 2) * Time.deltaTime);
       float height = 0;
       Vector3 terrainPos = Vector3.zero;
       terrainPos = transform.GetComponent<ViewHelper>().underHit.collider.gameObject.GetComponent<Terrain>().transform.position;
       height = transform.GetComponent<ViewHelper>().underHit.collider.gameObject.GetComponent<Terrain>().SampleHeight(transform.position);
       transform.position = new Vector3(transform.position.x, terrainPos.y + extraHeight + height, transform.position.z);

I need to create the most smooth motion possible. Any help is appreciated.