Dredging b-ways

[cheferson]

What effect on the fishing does a newly(couple months )dredged b-way have? Does it kill the fishing because of lost structure, or does it get better because of increased water flow?

[rhody]

According to Daignault it greatly improves the fishing.

[rizzo]

The flow (cubic feet per second) doesnt increase technically. The same amount of water still needs to move through because of the tides.

Before the channel is dredged the water would have to move faster (velocity or feet per second) to get the same amount of water out because there is less cross sectional area for the water to move through. Once the channel is dredged there is a greater cross sectional area for the water to move through so the veloctiy slows.

So once the channel is dredged the water would actually move slower, but would offer more depth. I'm not sure how much they dredge or if the effects are noticable though.

[STREETFIGHT]

i have heard they will bring it down to 30 feet in the channel and 60 feet in the sediment basins (sounds deep to me...) i've heard from some old timers that in the past when the pond has been dredged (and maintaned) the colder / deeper water will hold "big" bass all summer and that the fishing is very good.

[SeaWolf]

they are not dredging the channels, but the deltas (where the channel opens up to the back of the ponds. they will be dredging a couple spots through the channel to the pond. they will not be touching any of the breachways themselves. the primary focus of the project is to increase life in the deltas and the ponds, restructuring the deltas, increase habitat for smaller species in the ponds, and plant eel grass.

[parker23]

Ok, here goes.
My Grandfather always talked about the Venturi Effect of outflows/inflows of water and its relation to fishing rips/currents. When the opening is increased by overall volume, water speed decreases. Pretty straight forward.

However, think about the subtle eddy that forms behind a small outcropping, that produces fish at certain stages of the tide. Or the prized end of the jetty during the ebb tide that you have studied for years, has change in every way imaginable. Will the fish hold closer due to the reduced speed of the current? Years ago we fished a sandbar in Mass that consistantly produced bass in the dog days of summer. There was a railroad bridge north of the bar that provided a nice stiff water flow. They dredged the area 15 years ago, which reduced the water speed by half. It took us a few seasons to figure out the new hot spots on the bar.
Which at the time was rather annoying, but in retrospect I am a better fisherman (in my opinion) because of the change. New bars/shallow areas formed as well as holes were created by the change in curent speed (Venturi Effect). Some change is good. We can re-learn our favorite spots.

Mother nature changes our favorite beaches every storm, new bowls/bars/rips are created everytime a good blow hits the beach.

I am sure the dredging will be monitored to the nth degree by the appropriate agencies. If the pond capicity is increased, the water will stay cooler longer, holding more fish/bait.

Bring on the change mother nature/mother gov"t. Learning is good! Once you stop learning, time to hang it up.

[Bill L]

http://www.nae.usace.army.mil/news/2004-102.htm

[RIROCKHOUND]

A geologists perspective..
I'm not an expert in this type of coastal geology; I'm more of a beach and glacial geologist, but here goes...
Seawolf is right; the dredging project in C-town is designed to "restore" (read change) the Flood tidal delta (FTD) from an inter-tidal habitat (wading birds etc) back to a subtidal eelgrass habitat. In the channel they will be digging a sedimentation basin to capture sediment coming into the inlet before it can reach the FTD, and bury the newly planted eelgrass, then the basins can be dredge as needed to keep the project going, but this is RI, who knows if the maintenance dredging will happen. A FTD is defined simply as the accumulation of sand landward of the inlet throat, shaped chiefly by flood-tidal currents... Basically there is a reason there is sand there in the first place, and it will likely go back there again...

That was all eelgrass habitats at one point, and they want to restore it. Habitat restoration is a hot button issue lately, even though it is really change, since one habitat is there already.
My opinion is twofold 1; the sedimentation basins will/could fill up with one good storm (read Hurricane passing west, onshore surge etc.. or a very powerful Extra-tropical storm (SE’er that persists for an extended period (a few days)) Get another sizable storm before the next round of dredging and there willbe alot of sand back in the inlet headed for the FTD
. 2. Eelgrass has not done well in recent years in the salt ponds (coastal lagoons technically, salt ponds is a local name) because of Nitrogen coming in from the septic systems of the houses on the ponds... Those houses on the barrier are built on sand, the houses on the back of the pond are built on sandy glacial delta deposits that generally dip seaward (to the south) the sewage doesn’t have a very long residence time in the leach field,, and Nitrogen goes into the ponds... Remember, these are my opinions, but check back in a few years......

30ft and 60ft are VERY deep, especially when you consider the width, the channel would never be stable at that width/depth, for some reason the number 18ft for the basins is sticking in my head, but that may not be true.. That is being plucked from way back in my head...,

As far as changes in current, the tidal range in the lagoon probably wont change appreciably, the width of the inlet relative to any depth change is very large, and water is still fairly restricted into and out of the pond by the shallowest and narrowest points of the inlet. Since that isn’t going to change, the current probably wont change much. Current flow will likely slow a bit at the basin (which is why the sediment is supposed to deposit in the basin, through a process known as flow separation) but overall I suspect it wont change much.

For the health of the pond, I hope the project succeeds, the eelgrass would be beneficial habitat for winter flatties, schoolies, etc.. But my gut feeling says in a few years there wont be much eelgrass left where they dredged...


Bryan

[turfandsurf]

For everyone's information on the dredging of Charlestown breachway. I was there on Sunday fishing and they were getting things ready for dredging. Pipe which was about 12 inches thick and about 1/4 mile long was run from boat launch and down the road to about 1st house on the road to the beach. Looks like they will be dredging soon. There was a machine that looks like it would do the dredging and the workers had a boat to motor around in. It looked like the pipe would be dumping the sand on the beach by the 1st house.

[RIROCKHOUND]

Yup, the pipe extends down to the first two houses (East of the breachway) the predominant longshore transport is to the east, so this sediment should move down the beach towards green hill etc.. Of course one good SE blow could put it all back inside the inlet, or take it offshore where some of it can come back offshore and some will be lost from the coastal sysetm (basically we think that below 12m, it cant get back onshore), but we'll have to wait and see

[fishgolf]

Wow....u guys are awesome!
I like the technical stuff

[cheferson]

Yeah thanks for the info guys!

[Nebe]

just think of all the smiling bills that are going to be shooting out of that pipe

[cheferson]

More then a handful of mine . Thats where i learned how to use a bucktail! Guys were getting schoolies on plastics and wood while i was hammering keepers on bucktails.

[RIROCKHOUND]

I'll be there tommorow for work; I'll take some pics If I remember the camera...

[zacs]

I would love to see pics! I can't get down there until next week.

[RIJIMMY]

That is great info. I think the bway channels and ponds are some of the most under-fished areas. In my kayak I have seen big bass in broad daylight swimming up the channel or laying in the holes.

[cheferson]

Any pix rock?

[RIROCKHOUND]

Yeah.. but on a major deadline for work, wont have time to re-size and post till at least tommorow, or fri...
B

[spence]

Please OAK. Chef doesn't have anything to do until they get the Netflix hooked up

-spence

[kippy]

[QUOTE]Originally posted by spence
[B]Please OAK. Chef doesn't have anything to do until they get the Netflix hooked up

Chef, you should contact Eben about a blowing job..

[Nebe]

Originally posted by kippy

Chef, you should contact Eben about a blowing job..
[/B]

hey watch it mister...I dont swing that way

[kippy]

[cheferson]

Already got netflix baby!! Sighned up sunday, got first 3 movies tuesday, already watched 8 movies! Your just jealous spence! I have payed into unemployment too by the way, i worked 2 jobs 60+ hours a week all summer. Not my fault my job is seasonal, go book some parties at the OC and maybe theyll call me back. Ill be thinking about you spence when im up north getting paid to snowboard

[bart]

[RIROCKHOUND]

Finally.. sorry for the wait Chef
More pics to come when I can get down there during pumping, probably tommorow, but it could be later today if I get the ambition to get out of the office...
B

Pic 1 The dredge.. as you can see they are in on the Flood tidal delta, not in the breachway itself...

[RIROCKHOUND]

Pic II a look at the ~12" pipe; the fitting on the end shoots it up in the air so it doesnt form a channel on the beach at the outlet (it does a bit but they pumped ~12hrs before these pics and the beach was back to "normal" ie no obvious scour from the pipe

[RIROCKHOUND]

Pic III the outleft of the pipe

[RIROCKHOUND]

Pic IV the scarp, which is the semi-vertical face in the beach is not induced from the pumping that was the result of the SE'er we had about 10days before this pic was taken..

Also, there were two locals down there when I was, checking things out.. one was a very nice "swamper" named Tom.. the other tried to tell me that by driving on the beach in Sept-Dec, thats why the owners of the house has a beach come spring/summer... he also ripped URI... I didnt tell him I was a geologist at URI... if anyof you think that driving on the beach preseves the beach ..... it doesnt hurt the beach persay, but it doesn preserve it....

[piemma]

You think the Rock man is awesome here! You should fish with him in the middle if the night. I go home knowing more than any mortal should about beach erosion, silt, tidal flow. He is a veritable storehouse of valuable info.