The shape of the hydrograph varies according to a number of controlling factors in the drainage basin A number of factors (known as drainage basin controls) influence the way in which a river responds to precipitation and have an effect on the shape of the hydrograph. The size, shape and relief of the basin are important controls. Water takes longer to reach the trunk stream in a large, round basin than in does in a small, narrow one Where gradients are steep, water runs off faster, reaches the river more quickly and causes a steep rising limb.
Prolonged heavy rain causes more overland flow than light drizzly rain. Different river catchments produce different shapes of hydrograph. A ‘flashy’ hydrograph has a short lag time, high peak discharge, and steep rising and falling limbs; a ‘damped’ hydrograph is the opposite. Urban development is likely to make a river catchment more ‘flashy’ and prone to flooding, because of rapid runoff from impermeable tarmac surfaces into streams. Hello MAtthew The shape of a hydrograph changes according to a number of controlling factors in the drainage basin.
An example is if there is a steeper gradient on the surface at which the water is running of it means that the water runs off faster and eaches the river quicker and causes a steep rise on the graph like on the Hydrograph of River Secton there is lots of discharge, compared to the River Dorth hydrograph at which the slope on the graph is shallower meaning that the surface is gentler. Also areas of permeable rocks and soil allow more infiltration to and so there is less surface runoff which means that the shape of the graph may change. The climate may change the shape of the graph as there is more likely to be more rainfall in winter than in the summer so the shape will be slightly different