Natural And Human Causes Of A Flashier Flood Hydrograph Flashcards
What are natural causes for a flashier flood hydrograph?
High rainfall intensity
Impermeable geology
High drainage density
Small basin
Circular Basin
Low temperatures
Type of precipitation
Vegetation cover
Antecedent rainfall
What are the three human causes for a flashier flood hydrograph?
Urbanisation
Pastoral farming
Deforestation
How does high rainfall intensity effect the hydrograph?
Higher discharge potential so more likely for soil to reach its field capacity
Increases surface runoff
Decreasing lag time
What is antecedent rainfall?
Rainfall that occurs before the specfic event like a storm or flood. It’s important as it affects soils saturation levels and therefore likelihood of flooding.
How does high drainage density effect the hydrograph?
Many tributaries to the main river
Increases speed of drainage
Decreases lag time
How does a small basin effect the hydrograph?
Rainfall reaches the central river more rapidly
Decreasing lag time
How does a circular basin effect the hydrograph?
Rainfall reached the river more rapidly
Decreasing lag time
How does lower temperatures effect the hydrograph?
Less evapotranspiration
Greater peak discharge
How does precipitation type effect the hydrograph?
Snow and hail have to melt before moving towards the river so slower lag time
Rain is a direct input so increases the risk of flooding
How does vegetation cover effect the hydrograph?
If it’s frosted then it will intercept more rainfall decreasing flood risk.
If the areas exposed then they will transfer water to the river rapidly decreasing lag time.
How does urbanisation effect the hydrograph?
More impermeable surfaces
Increased runoff
Surface storage and infiltration are reduced
How does pastoral farming effect the hydrograph?
Ground gets trampled by livestock
Less interception
More surface runoff
How does deforestation effect the hydrograph?
Less tree interception
Water reaches ground and rivers quicker
More surface runoff
Greater flood risk
