The document discusses the main factors that affect runoff from a catchment area. It lists seven factors: 1) precipitation characteristics like intensity and duration, 2) the shape and size of the catchment, 3) topography such as slope, 4) geological characteristics of the surface and subsurface, 5) meteorological characteristics like temperature and humidity, 6) the character of the catchment surface such as whether it is cultivated or drained, and 7) the storage characteristics of the catchment including natural depressions or artificial reservoirs. Each of these factors can increase or decrease the amount of runoff from a catchment area depending on the specific characteristics.

2. Name:- Devani Mayank Z.
Branch:-Civil 4th
Er. no:- 126800306036
Sub:- Factor Affecting
RunOff
Collage:-A.I.E.T

3. Factor Affecting Of Runoff

4. The main factors affecting runoff
are:
1. Precipitation Characteristics.
2. Shape and size of the catchment.
3. Topography.
4. Geological characteristics of the cathment.
5. Meteorological characteristics.
6. Character of the cathchment surface.
7. Storage characteristics of the catchment.

5. 1. Precipitation characteristics
The important characteristics of precipitation are
 Intensity of rainfall
 Duration of rainfall
 Form of precipitation
 Direction of strom movement
etc.

6. Runoff increases with the intensity of rainfall.The
more the rainfall,more will be the runoff. Also the rainfall
for a longer duration would produce greater runoff.
The precipitation may occur either in the form of
Rain or snow. If the precipitation occurs in the form of
rain. It will immediately produce the runoff but if
precipitation occurs in the form of snow. It will produce
the runoff much later.

7. 2.Shape and size of the
catchment
The runoff is considerably affected by the
shape and size of the catchment.A drainge
basin may be either fan shaped or fem-leaf
shaped,in case of fan shaped catchment,all the
tributaries are apporoximately of the same size
such catchment gives.greater runoff since peak
flood from the tributaries is likely,to reach the
main stream apporoximetly at the same time.
In the case of fem-leaf shaped catchment
the tributaries are generally of different
lengths,and meet the main stream at the regular
intervas.in such a narrow catchment, the peak
flood intensity is reduced.

8. 3.Topography
The topography of the catchment area has
significant effect on the runoff.A steoply sloping
drainage basin produces greater runoff,because
a steep slope helps quicker draingage,no
depression storage,and less evaporation loses.
If the catchment is mountainoys,and is
locater on the windward side of the
mountains,the intensity of rainfan will be
more,and hence runoff will also be more.

9. 4.Geological caracteristics of
thecathment
The runoff is also signifcantly affected by the
geology of the drainage basin.these include the
type of surface soil and sub soil type of rock and
their penebility.
If the surface soil and subsoil is pervious,
sepage will be more and this turn reduces the
peark flood.if the surface is rock,the water
abscorftion will be very small and runoff will be
more.however,if the rocks have fissures or if
they are porous, most of the water be lost by
way of seepage and surface runoff will be very
small.

10. 5.Meteorological characteristics
Temperature
Hymidity
Wind velocity
Pressure variation ,etc.
Higher temperature and higher wind velocity
cause more losses due to evaporation and
transpiration and hence reduce the runoff on the
other hand,greater hymidity decreases
evaporation and transpirtion losses,resulting in
greater runoff.the variation of pressure storms
causing the precipition.

11. 6.Character of the catchment
surface
The runoff also depends upon the
surface condition whether the surface is
drained or undrained,natural or
cultivated,bare or coved with uegetation
etc.
If the surface has no natural
drainge,absorption loss will be more,if
more area of catchment is cultivated
surface runoff will be less.

12. 7.Storage charcteristcs of the
catchment
If a drainage basin has a large number of
natural depressions,pools,lakes,etc.which will
store a part of precipition ,has a tendency to
reduce the peak flow.simillarly,creation of articial
reservoirs or tanks will also increase the storage
capacity of a drainage basin, resulatiny in the
reduction of the runoff.

13. Any
Question ?

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