GEOL 118 Lecture Notes - Lecture 35: Heavy Rain, List Of Lakes By Volume, Hydrograph
Document Summary
Geol 118 - lecture 35 - floods i. Flood = river overflows its channel due to excessive discharge. Floods are normal, natural events that occur along rivers. For average river in humid climate, flooding typically occurs every ~1-2 years. Most widespread geologic hazard, affecting more people than all other geohazards combined. In us, ~20,000 communities, 7 million buildings, 6 million homes (10% of us population) are located on flood-prone land, resulting in ~ billion of damage and ~80 deaths per year. Annual damage from floods in usa has increased by factor of 30 over 70 years after adjusting for inflation. Among 26 moderate to large cities studied by usgs in 1974, ~50% of floodplain was developed. Asia has much higher death rate from floods even accounting for its higher population because more underdeveloped. Heavy rain- water runs quickly over land into river rather than infiltrating into ground, where it moves slowly.