I just found out that 6 inches of rain fell in Santa Barbara when the erosion occurred on our property (actually 10 inches we found out later from the weather people)

 Since we are on a steep hill it protects us from most flooding down in the valleys. However, if you get 6 inches of rain within a few hours or so on top of a mountain there is really nowhere for that water to go but basically straight down the mountain. So, all flood control measures would be defeated by 6 inches of rain in a few hours in any location in Southern California.

I just found out from neighbors that the 6 inches of rain actually was 10 inches of rain they found out later from the weather people in our area of Santa Barbara. This explains the extreme amount of damage in our particular area.

We are going there tomorrow to Santa Barbara to temporarily fix the problem before our Landscaper can bring in boulders to stop the problem more permanently during the next week or so.

However, it's going to rain again Thursday Night so I have to address this so the water doesn't undermine our driveway or eventually our house on a steep hill.

In the Past in California you mostly were worried to be living in valleys where all the water has to eventually go. However, now you have to worry more about suddenly getting 10 inches of rain and having your driveway and home undermined by 10 inches of rain suddenly if you live on a Hill ANYWHERE in Southern California this year and likely every year from now on.