[Acoustics] mode use for slow vel

[Nick Wray]

I tend to towards WM11 BM 5 for the very low velocities on the R Nene
here in the UK approx 0.006 m/s at this time, .You do need a lot of
patience and two good guys on either bank pulling the boat very slowly
and steadily much harder than it looks at low speeds.as James mentioned
variable wind speed,boat speed,and negative/variable  flows,and u/s d/s
lock operation not forgetting weed, all make for difficulty getting
repeatable transects within the 5% range. With a dynamic entity like a
river All you can do is try and be consistent with your transects, do
many until your happy you have covered the river flows "pulses" and look
at the mean.

Nick  
>>> James J Duncker <jduncker at usgs.gov> 14/09/2006 15:26:28 >>>
Dave;
As others have mentioned, mode 5 should work, but at really low
velocity 
situations, are you sure you have steady flow?  We've found that a lot
of 
factors (boat speed, edge estimates, variable wind speed, upstream and

downstream controlling works, etc) can influence the flow in low
velocity 
settings to make it difficult to get  "repeatable transects".

Jim
 
James J. Duncker
Hydrologist
U.S. Geological Survey



David M Hernandez <dmhernan at usgs.gov> 
Sent by: acoustics-bounces at simon.er.usgs.gov 
09/13/2006 11:50 AM

To
acoustics at simon.er.usgs.gov 
cc

Subject
[Acoustics] mode use for slow vel







To all, The conditions are: Channel width 100 to 200 ft. Depth 3 to 7
ft. 
velocity < .1ft/sec. Used Rio 1200khz water mode 12sb bottom mode 5.
Not 
sure it was the best combination for those conditions, does anyone have

similar conditions? Which mode combinations would work best for
collecting 
repeatable transects?
Dave_______________________________________________
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