measure v (current-meter) at 0.2 and 0.8 of depth average v and multiply by (width * depth)

• Measure V (current-meter) at 0.2 and 0.8 of depth

• Average V and multiply by (width * depth)

• Sum up across stream to get total Q = (Vi Di Wi)

Stream Cross-Section for Q

Rating curve hysteresis loop in Zenne river (Lot), 15-16 July 2012 event: blue triangles – rising stage, green squares – falling stage

CR

k s 1 1 2

ln

Flume tests carefully conducted by Nomicos (1957) at CalTech:

constant-depth, unique sediment size d=0.152mm

difficult to reconcile with the standard formulation for the ‘alluvial resistance coefficient’:

.

Bed-material discharge

Bed morphology adaptation

Alluvial resistance

Buoyancy-affected turbulence

10

32Sc

mU

BF

BF Dgcwith

2

tanh2

1m

Rdetached x

Umf 2

2 detachedfS

)1( m

If BF is the wavelength from crest to crest, the celerity of the associated gravity wave is given by Airy’s law:

BF

Dgc

BF

2tanh

2

BF

BF

Dg

BFattachedf

2tanh

2

1 attachedfS

1

2

attached

detached

f

fS

BF

Dg

UmS

BF

2tanh

2

2

310

detached

attached

f

fS

Facteur m

m = 1,1 m = 1,2

10

32Sc

mU

BF

BF Dgcwith

2

tanh2

1m

Discontinuity rating curve

original discontinuity rating curve Modified discontinuity rating curve