High-water Level River Discharge Measurement Method in Japan

Technical Problem of Measurement using
Floats.2(Hypothesis on Disturbed flow in the downstream of bridge piers)
Actual discharge value:Q
Q
Non-back flow field
Back flow field
Discharge observed value based on the current standard Q’
Q 1 =A 1
Q 2 =A 2 V 2
Non-back flow field
Q 1 Discharge of non-back flow field ,A 1 river area of non-back flow field,
V 1 average velocity of non-back flow field,
Q 2 Discharge of back flow field,A 2 river area of back flow field,
V 2 average velocity of back flow field
V 1
Q=Q 1 +Q 2
=A 1 V 1 +A 2 V 2
Q 1 =A 1 V 1
Q
Non-back flow field
Q 1
=A 1
(V 1
+V
)
Back flow field Q 2
=A 2
(V 1
+V
)
Q’= Q 1
+Q 2
=(V 1
+V
)(A 1
+A 2
)
Non-back flow field Q 1
=A 1
(V 1
+V
)
Q 1 Discharge of non-back flow field,A 1 river area of non-back flow field,V 1 average velocity of non-back flow field,
V acceleration by aboideau rising effect,Q 2 Discharge of back flow field,A 2 river area of back flow field
comparison of Discharge observed value of current standard and Actual discharge observed value
Q’=Q+(V 1 -V )A 2 +V (A 1 +A 2 )
Discharge observed value based on the current
standard has overestimates the river discharge
The part become exorbitance
caused bythe underline part
Tone River downstream construction office
Tone River downstream part river bed and discharge observation research report in 1999