Impact Hazards - Start here, but be sure to look at reserve books, articles in Scientific American, Nature, Science, Sky & Telescope
 
Asteroid and Comet Impact Hazards (NASA)
 
Planetary Defense Workshop (LLNL 1995)

Asteroid Impact Simulations (Asphaug, UCSC)

Terrestrial Impacts (NASA)

Terrestrial Impacts (Hamilton, Views of the Solar System)
 

Tsunamis (Australian Spaceguard Survey)

Double Whammy: Land or Sea? (Scientific American)

News articles, individual pages- good for leads, insight but not primary reference material 

Asteroid Hazard Study (Cornell News 2000)

Killer Asteroids, the Count Rises (Sky and Telescope 2001)