The ratio of the total length of streams of all orders within a basin to its area is called ________. 

Explanation

• Drainage density: It is defined as the sum of lengths of all the streams divided by the catchment area.
• Drainage Density = (Total Length of Channels/Catchment Area)

Factors affecting Hydrograph:

a) Shape of catchment: Hydrograph from a catchment with a broader end near the outlet has a higher and early peak.

(b) Compactness factors: It is defined as the ratio of perimeter of catchment to the perimeter of form circle. Form circle is the circle having the same area as that of the catchment.

As the compactness factors decreases, average length of travel to the outlet decreases, hence decreasing infiltration and increasing resultant discharge.

(c) Catchment slope:

In general, as the slope of catchment increases, flow velocity increases, thereby decreasing the infiltration and decreasing the base period and increasing runoff discharge. For small catchment when overland flow is more dominant, general land slope plays more important role, whereas for large catchment where channel flow is more dominant, main steam slope plays a more important Role.

(d) Drainage density: It is defined as the sum of lengths of all the streams divided by the catchment area.

In general as drainage density increases, flow velocity increases, infiltration decreases, base period decreases and peak discharge increases.

(e) Land use: Urbanisation reduces infiltration by increasing flow velocity, thereby decreasing the base period and increasing the peak of the hydrograph.