Just to add to clandestino's post (that "times ten" rule is one I've not seen before, but sounds useful .. must check for our types ..)
A typical rule of thumb used for assessing safety implications of runway excursions goes something like:
- 40kts and below : "major" - damage and injuries, no deaths
- 40 to 70 knots : "hazardous" - serious damage, risk of death
- 70 plus : "catastrophic" - hull loss, multiple deaths
Now, there are of course exceptions (good and bad luck) but it's a decent average.