Old vs new way of reading the bottom on the Mississippi

I used to rely almost completely on my depth finder and just go by the numbers. Then about 4 years ago I switched to running a towed sonar array behind the dredge and it changed everything. The old method was fine for basic depth but it missed all the subtle changes in the bottom type. Now I can see clay turning to sand before I even hit it, which saves me from chewing up a cutterhead. A guy up near Baton Rouge told me to try it after I burned through a set of teeth in one shift. Has anyone else made the switch and found the same thing or do you think the old way still works better for certain conditions?

3 comments

3 Comments

emma_clark12d ago

You're off on the towed array part. Those arrays are for seismic surveys, not real time dredge work. What you're talking about sounds more like a sidescan or multibeam echosounder towfish. My buddy runs a dredge up in Greenville and he's got a multibeam setup that shows him bottom hardness in color coded layers. But even that won't tell you clay from sand until you're basically on top of it. The real trick is something different. We started running an acoustic doppler profiler mounted on the ladder that shoots a beam ahead of the cutterhead. That little unit picks up density shifts in the water column about 50 feet ahead, which is enough to slow the swing before you hit hard bottom. Saved me a cutterhead rebuild last spring when we ran into an old submerged riprap pile nobody marked on the charts. Your guy up near Baton Rouge might have been running something else entirely, or maybe he just meant a basic fishfinder rigged sideways.

simonh7412d ago

Take that acoustic doppler idea and run with it harder. We mounted one on our ladder two seasons back and paired it with a small tablet running custom overlay software that gives us a real-time color bar showing density shifts, not just raw numbers. It caught a buried tree trunk wedged in the mud before we even got close enough to worry about it, which to me is worth the setup hassle alone.

evan_burns9512d ago

Man, I gotta say I was pretty skeptical about the whole doppler on a ladder thing till I read this. I always figured you'd get too much interference from the cutterhead vibration to make any sense of the data. But hearing it caught a buried trunk before you even saw it? That's enough to make me rethink my whole setup for next season.