2. Hydrographs Flashcards
What is a hydrograph?
A graph that visuals the response of river’s discharge to a rainfall event
It shows rainfall in a bar graph and river discharge in a line graph.
What does peak rainfall refer to?
The point in time when rainfall reached its max
What does peak discharge indicate?
The point in time when discharge reached its max
Define lag time in hydrology.
The time between peak rainfall and peak discharge
What is the rising limb of a hydrograph?
The upward-sloping curve of the discharge line
What is the falling limb of a hydrograph?
The downward sloping curve of the discharge line
What is throughflow?
The section of the discharge made up of water reaching the river via the soil layer
What does throughfall refer to?
Water flowing to the surface from leaves and the trunk of the tree
Define surface run-off.
The section of the discharge made up of water reaching the river via overland flow
What is base flow?
The amount of water that would always be in the river regardless of rainfall
What is the significance of lag time in a hydrograph?
It measures the time it takes for the river to reach peak discharge after peak rainfall
What factors influence how rivers respond to rainfall?
Size and shape of the drainage basin, rock and soil type, density of vegetation, degree of human influences
What is drainage basin density?
The length of streams in relation to the area of the drainage basin
What is drainage basin frequency?
The number of tributaries and streams in the drainage basin
What influences the pattern of tributaries in a drainage basin?
Its water balance between run-off, evapotranspiration, and storage
How does vegetation cover affect river discharge?
It intercepts rainfall, slows it down, and encourages throughfall, leading to lower peak discharge
What happens to discharge in areas with bare ground?
It increases surface run-off, creating flashy responses with high discharge levels and short lag times
How does the relief of a drainage basin affect run-off?
Steep valleys increase surface run-off while gentle slopes promote infiltration and throughflow
What role do impermeable surfaces play in river discharge?
They lead to quick run-off and flashy responses in the river
What is a river regime?
The flow of water in a river over a year showing how seasonal changes influence flow
What factors impact flood recurrence?
Vegetation density, urbanization, and river modifications
How does forest cover affect flooding?
It intercepts rainfall and leads to greater rates of transpiration, reducing flood magnitude and frequency
What are some human modifications to rivers?
Dams, reservoirs, channelized rivers, and diversion channels
What is the goal of softer approaches in river management?
To work more closely with nature and increase storage capacity across the drainage basin
Fill in the blank: The _______ is the amount of water that would always be in the river regardless of rainfall.
base flow
True or False: A large drainage basin reaches its peak discharge faster than a small drainage basin.
False
