Question

Highest momentary peak discharge at the respective point of observation in river flow, which is equalled or exceeded once every year, is known as:
1. back water
2. avulsion
3. annual flood
4. base flood

Answer 1

Correct Answer - Option 3 : annual flood

Concept:

Avulsion:

• It is a natural process by which flow diverts out of an established river channel into a new permanent course on the adjacent floodplain.
• Avulsions are primarily features of aggrading floodplains.
•  Avulsions cause loss of life, property damage, destabilization of shipping and irrigation channels, and even coastal erosion as sediment is temporarily sequestered on the floodplain.

​Annual flood:

• It is the highest momentary peak discharge at the respective point of observation in river flow, which is equaled or exceeded once every year.
• The highest flow at a point on a stream during any particular calendar year or water year.

Base flood:

• A flood having a recurrence interval that has one ­percent chance of being equaled or exceeded during any given year (1-­percent-­annual-­chance flood). 

Backwater:

• If a river has developed one or more alternative courses in its evolution, one channel is usually designated the main course, and secondary channels may be termed backwaters.
• The main river course will usually have the fastest stream and will likely be the main navigation route; backwaters may be shallower and flow more slowly.