The process of cavitation in water has been involved in the damage of many types of man-made structures. Shock waves and water jets caused by the collapse of cavitation bubbles can clean, dent, or even pulverize materials of many types, including concrete and metals. The physics of cavitation damage is reviewed. Flow speeds greater than 30 m/s appear necessary for cavitation damage, but thereafter the damage potential can increase rapidly, perhaps at rates proportional to the sixth power of velocity. Major damage can occur with flow depths of only a few meters. Damage potential decreases with flow depth because increasing pressures make it less likely that internal water pressures can be dynamically forced to become less than the vapor pressure of water. Cavitation damage is greatly lessened as the air content of the water is increased, suggesting that cavitation damage is unlikely to be found in "white water" rapids. The roughening of water channel surfaces also decreases cavitation damage by slowing the flow speeds and thereby increasing flow depths for constant flow discharge. Damage initiated by cavitation can provide opportunities to accelerate the rates for normal erosion processes as water plunges into the holes created by cavitation.