Lesson 4 - Storm hydrographs

Question 1

What is a storm hydrograph?

Answer 1

A storm hydrograph is a graph showing changes in the discharge of a river over a short period of time.

Question 2

What is the impact of an increase in surface run-off on the risk of flooding in a drainage basin?

Answer 2

An increase in surface run-off increases the risk of flooding in a drainage basin.

Question 3

Define the term peak precipitation?

Answer 3

Peak precipitation is the highest amount of rainfall per time unit.

Question 4

Define the term rising limb?

Answer 4

Rising limb shows how quickly the discharge rises after a rain storm.

Question 5

Define the term peak discharge?

Answer 5

Peak precipitation refers to the highest recorded discharge following a rainfall event.

Question 6

Define the term lag time?

Answer 6

Lag time refers to the time difference between peak rainfall and peak discharge.

Question 7

Define the term falling limb?

Answer 7

Falling limb shows the reduced discharge once the main effect of runoff has passed.

Question 8

Define the term base flow?

Answer 8

Base flow is the normal flow of a river when its water level is being sustained by groundwater flow.

Question 9

Define the term bankfull discharge?

Answer 9

Bankfull discharge does not always appear. It marks the level of discharge above which flooding will occur.

Question 10

Give some of the characteristics of a flashy hydrograph?

Answer 10

• Short lag time
• Steep rising limb

Question 11

Give some of the characteristics of a subdued hydrograph?

Answer 11

• Longer lag time
• Gently sloping rising limb