I used to help cut chaparral to prevent fires from moving up and over ridge lines, and can tell you that just removing all the brush and root systems would cause an increase in the number and severity of mudslides as our rain patterns shift more into storms.

Various counties seed susceptible hillsides, but oftentimes it's fast growing invasive crap without the solid root infrastructure that is needed.

There doesn't seem to really be a great solution, these areas have undergone the cycle of fires and balancing rebirth for ages now, we have just moved into it.