Summary - Geography- Hydrographs

HYDROGRAPHS:
 Hydrographs show the response of a river to a rainfall event. It plots
rainfall and river discharge
 Lag time is the time between peak rainfall and peak discharge
 Rivers with a short lag time respond rapidly to rainfall events and
are therefore more prone to flooding.
 Rivers with a long lag time respond slowly to rainfall events and are
therefore less prone to flooding
Flashy hydrograph Causes Subdued hydrograph
Low infiltration Infiltration rates High infiltration
capacity capacity
Snow thaw in the Precipitation Light rainfall
spring
Steeply sloped land Relief Flat/ gentle sloped
land
Clay-like soil Soil type Sandy soil
Impermeable rock Rock type Permeable rock such
such as granite as sandstone
(igneous) (sedimentary)
High drainage Drainage density Low drainage density
density (more (less tributaries)
tributaries)
No rain in area Antidecent May have rained
previously so soil is conditions previously, less water
able to absorb is able to infiltrate soil
rainfall
Urban areas Land use farmland
(urbanized,
impermeable areas
High tide Tide and storm Low tide
surges