One that only occurs once each century.
The flood that resulted in the most damage during the last century.
The flood with the highest water level recorded in the last century.
A flood with a 100% probability of occurring within a given century.
A flood with a 1% probability of occurring within a given year.
Amount of dissolved gases
Duration of the eruption
Whether the eruption occurs on a continent or an oceanic island
Length of time that has elapsed since the last eruption of the same volcano
Body waves that cause the ground to move in a rolling fashion
Surface waves that cause the ground to move laterally, side-to-side
Surface waves that cause the ground to move in a rolling fashion
Body waves that cause the ground to move in a push-pull fashion
Body waves that cause shearing of ground as they pass
In a down-cutting direction.
Laterally, toward the outside of the meander bend.
Laterally, along the inside of the meander bend.
Laterally, along both banks of the stream.
The size of the drainage basin involved.
The gradient of the stream channel.
The absolute discharge of the stream.
The value of discharge per unit area of stream
The length of the stream.
Narrow flood plain
All the above
a and b but not c
Damage from volcanic eruptions
Damage from landslides
Covering porous and permeable soil with streets and parking lots, which increases the runoff to infiltration ratio for rainwater.
Installing storm sewers along streets and residential neighborhoods, which decreased the time it takes water to reach a stream channel
Elevating structures built on the floodplain, to keep them above the flood waters, which reduces the volume of available storage capacity for the flood waters, forcing them to go even higher.
All the above
B and c but not a
Pyroclastic flows and falls
Burning brimstone (sulfur)