Lesson 2 – page 1

 To learn what is a flood hydrograph  To learn how to read a flood hydrograph  To learn what is:  Lag time  Peak discharge  Rising limb  Falling limb  Base flow.  Key Skill = Application of number

 Lag time = time between peak rainfall and peak discharge.  Peak discharge = point when river flow is highest.  Base flow = water entering the river from beneath surface.  Rising limb = part of graph when flow is increasing.  Falling limb = part of graph when flow is falling.

 Draw your own labelled version of the flood hydrograph.  Explain the terms:  Lag time  Peak discharge  Rising limb  Falling limb  Base flow.  Using the scale, calculate: ◦ Lag time ◦ Peak discharge

 Explain what a steep rising limb and high peak discharge shows about a river.  What features of a drainage basin might cause this or stop it?