Hydro graphs

• What is hard engineering management in flood management?

  Using artificial structures, such as dams and embankments
• What is soft engineering management in flood management?

  A more natural approach to manage flooding, such as flood plain zoning
• What are the two main types of flood management strategies?

  • Hard engineering management
  • Soft engineering management
• What does a hydrograph show?

  How a river responds to a period of rainfall
• What is peak discharge?

  The volume of water in a river passing a point in a given time
• In what units is peak discharge measured?

  In cumecs (cubic metres per second)
• What is peak rainfall?

  The maximum amount of rainfall measured in millimeters
• What is lag time in the context of a hydrograph?

  The time taken between peak rainfall and peak discharge
• What does the rising limb of a hydrograph represent?

  The increase in discharge on a hydrograph
• What does the falling limb of a hydrograph indicate?

  The return of discharge to normal/base flow on a hydrograph
• What is base flow in a river?

  The normal discharge of the river
• How does vegetation affect lag time?

  Vegetation can increase lag time by intercepting rainfall
• What factors influence lag time?

  Size of the drainage basin, vegetation, valley side steepness, and soil type
• What are the factors influencing lag time in a hydrograph?

  • Size of the drainage basin
  • Vegetation
  • Valley side steepness
  • Soil type