Sediment detachment by water

Splash Detachment and Transport

（剥離）

（スプラッシュ：飛沫）

a) Pounding of the surface – and compaction

b) Rearrangement of the surface to create mechanical crusts

c) Detachment and transport

EFFECTS OF ENERGY OF FALLING RAINDROPS

（圧密）

（クラスト：土壌表面に形成される薄層構造）

3.5 mm droplet impacting at 6.13 m s-1

200 – 212 μm dry sand

Image sequence at 3000 fps

Sequence duration 0.11 s

200 – 212 μm dry sand

2.5 mm droplet impacting at 5.94 m s-1

Trajectories of splashed particles

Dynamics of Runoff And Erosion Modelling (DRÆM)

tim

e

Dynamics of Runoff And Erosion Modelling (DRÆM)

Surface-profile measurement taken using calibrated images of the sand surface

Long et al. (forthcoming)

FIG. 7. Particle location tracks

according to particle type: a)

high velocity, low ejection angle,

high displacement, b) low

velocity, high ejection angle, low

displacement

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0 20 40 60 80 100 120 140

0.00

0.01

0.02

0.03

0.04

0.05

0.06

Part

icle

fre

qu

en

cy / d

D

Particle travel distance, D (mm)

PDF of travel distance

based on the Burr XII disrtibution

k = 0.71262

= 3.75778

= 14.116

Pro

ba

bili

ty d

en

sity f

un

ctio

n

0 100 200 300 400 500 600 700

0.000

0.001

0.002

0.003

0.004

0.005

0.006

0.007

Pa

rtic

le f

req

ue

ncy / d

D

Particle travel distance, D (mm)

Type b particles

Type a particles

Detachment by raindrop impact

Where KE is rainfall kinetic energy, k and b are parameters determined by soil type and h is water depth

bhekKEDET 0.1

（雨滴衝撃）

Flow detachment

Raindrop

detachment