AGR and SWE soil water conservation, water erosion and its types

1. Water erosion and their types
S.Samuel raj
2018048095

2.  It is the detachment and removal of soil material by water. The rate of erosion may be very slow
to very rapid, depending on the soil, the land scape , and weather conditions.
Basic Phase
 1. Detachment: individual grains separated from soil mass/matrix
 2. Transportation: detached grains transported over land surface land surface
 3. Deposition: soil grains deposited in new sites

3. 1. splash:
loosening & splattering of small soil particles caused by raindrops impacting a wet
soil surface

4. 2. sheet or interrill:
removal of thin layer of soil over an entire soil surface caused by water flowing across
soil surface

5. 3. rill:
occurs during/after rain or when snow melts, & involves concentration of flowing water into small
channels (<0.3 m) that are more turbulent & have greater scouring action than sheet flow turbulent &
have greater scouring action than sheet flow.

6. 4. gully:
In areas steeper slopes, flow of water from rills concentrated, forming deep channels

7. Stages in the
development of a
gully on a hillside
(Morgan 2005,
Leapold et al.
1964)

10. 5. streambank:
removal of soil from banks of running streams

11. 6. coastal/shoreline:
erosion of ocean, lake, reservoir shores by action of waves resulting from wind, tides,
currents, storm events, & boat traffic

12. 1 Falling Raindrops 1. Falling Raindrops
a. Energy of falling raindrops
i. kinetic energy of a falling body calculated as:
E = ½ mv2 m = mass of falling body g
v = velocity of fall cm/s
E = kinetic energy (ergs) (g cm2/s2)

13. Effect of raindrops
i. Breaks peds & clods into smaller aggregates & individual particles.
ii. Moves particles into new locations
iii. Compacts & puddles surface soil layer, ↓ infiltration & infiltration & ↑ runoff

14. Rainstorm intensity & energy
i. avg. drop size↑ as storm intensity↑
ii. threshold intensity at which rainfall becomes
erosive = 25 mm hr-1
iii. Relationship between KE& rainfall intensity (I):
KE = total energy, ft-ton/ac-inch for each inch of rainfall
I = rainfall intensity in inches/hr up to 3 in/hr

15. Vegetative cover
Vegetation acts as buffer

16. Running Water
a.Runoff is important cause of erosion
b.Runoff classification: sheet/prechannel (3-5 mm depth) or channelized flow (5 mm - >3 m)
c.KE of rain vs runoff (KE = ½ m v2)
Rain Runoff
Mass AssumemassoffallingrainisR Assume25%runoff,massofRO=R/4
Velocity Assume term. vel. of 8 m s‐1 Assumespeed of surfflow=1 ms‐1

17. Watershed Management by Madan Mohan Das & Mimi Das Saikia, PHI Learning Private Limited
& JVS Murty, New Age Publications pgno 52-56