1. River Processes and Pressures What are Hydrographs?

2. A hydrograph is used to show how a river responds to a period of rain. Falling limb Rising limb This axis measures the amount of water travelling down the river (the discharge This axis measures the amount of precipitation that has fallen during the storm This axis measures the time since the start of the storm This is the time between peak rainfall and peak discharge

3. A B C D E F Label your hydrograph with the following: Peak rainfall, time, peak discharge, rising limb, falling limb, lag time

4. Peak rainfall Lag Time Peak discharge Rising limb Falling limb Time Tom breaths a sigh of relief as his house seems to have escaped the flooding

5. Annotate your graphs with the following statements, justifying your choices. 1. Rob places sandbags by the door as he thinks the river might flood. 2. Sarah moves the family upstairs as the river has burst its banks. 3. The fishing contest is called off as it’s considered too dangerous. 4. The Environment Agency removes the flood warning from the river. 5. The referee calls off the football match after a pitch inspection.

6. Steepness of slope

7. Landuse

8. Channel Density More river channels allow water to enter the main channel more easily Fewer river channels results in more overland flow and throughflow

9. Rock and soil type Impermeable rock e.g. Granite, or clay soil that allows little infiltration Permeable rock e.g. chalk, or sandy soil that allows plenty of infiltration

10. Intensity of rainfall Heavy rainfall event or rapid snowmelt Rainfall over a longer period of time, such as drizzle

11. Task The following situations will affect the storm hydrograph by producing either: a) a short lag time and steep rising limb, or b) a long lag time and gentle rising limb a rainstorm in an area underlain by granite a long period of 'drizzly' rain during summer a snowstorm in the Highlands of Scotland a thunderstorm in a city a rain event in an area which is heavily forested a period of showers in an area where there is much newly ploughed, fairly level, arable land For each of the situations listed above, select either (a) or (b) and give reasons for your choice

12. Intensity of rainfall a short lag time and steep rising limb A long lag time and gentle rising limb