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Currents in the C&D Canal

21K views 71 replies 12 participants last post by  mad_machine 
#1 ·
Refer to these messages here, then please post responses in this thread.
 
#10 ·
I am all in favor of currents when they help me get where I want to go; I am strongly opposed to currents which prevent me from going where I want to go...
Well the feeling's mutual - the currents oppose you almost as much as you oppose them! :laugher (Only "almost as much" because your motor power allows you to make some headway against them.)

It all depends on your frame of reference, which in the technical sense could be Eulerian or Lagrangian. (Now THAT will make your head spin! :p ) FYI, my PhD is in fluid mechanics, and I do still use some of this stuff in my day gig.
 
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#3 · (Edited)
Several factors control the current in the C&D canal

1. Tide amplitude on the Del River is 6ft., 1.5ft. on the Ches. Bay.
2. The Del River is a 'flowing river'.... adding to the tide height by virtue of its volumetric flow direction.
3. The Filling and draining of inlets, narrow rivers and canals usually 'lags' the high/low tide times, due to hydraulic geometries such as 'choke points', bottom contours, etc. etc. etc.

... all this means your really cant look at tide data and outguess what Historically is the actual flow direction in the C&D.
This historical data of 'actual' current flow, direction and strength is found in historically compiled data based on ACTUAL observation .... such as Eldridge Tide Tables ... and some 'programs' (probably based on Eldridge).

Rule of thumb for traveling the C&D going east, and to 'ride' the 'crest' of the outgoing tide all the way down to Cape May:
Gong 'east then down' - Leave the Engineers Cove at Chesapeake City 2 hours BEFORE low tide at Chesapeake City ... maintain 6kts. and ride 'the wave' all the way down the Del. Bay

Going north on the Del Bay, 'north then west': leave Cape May Point AT low tide or shortly before dead low, maintain 6 kts. and ride the tide wave all the way up the Del. Bay and through the C&D, expect the tide to turn AT Chesapeake City and ride the ebb down the Chesapeake to at least Baltimore/Annapolis.

Note: if there has been heavy rainfall in the Delaware Valley ... all bets are off as to 'timing' due to faster and increased water flow coming 'down'. Ditto with Heavy rainfall in the Susquehanna Valley and the Susque is 'backfilling' the C&D. Ditto but opposite effect with extreme drought in those river valleys.

Other: dont travel on the Del. Bay if there is strong NW or SE winds predicted or blowing, especially if youre 'against' the tide. 6-8ft. very steep chop is 'traditional' w/ strong NW/SW 'blows' on the shallow Del. Bay.
Other2: Only two places to anchor in 'protected water' on the whole Del. Bay between C&D and Cape May: 1. Cohansey River - with BIG tide/current flow, 2. Maurice River (way off the 'beaten path')
Other3: With 'light' winds, Expect to be 'eaten alive' by 'greenheads', stable flies, various gnats, and mosquitos during 'wet' or 'spring' - the reason nobody lives along the shores of the Del. Bay.
 
#4 ·
There may only be a few optimal or even best times to transit the C&D either way or with respect to ebb or flood in the Delaware, point of beginning and final destination.

Even if one selects the absolute wrong time, the maximum current in opposition will be for less than 1/4 of the transit.

On the evening of June 7th the maximum current in opposition will be about 1.5 knots, an extra pint of fuel and about 2hrs extra for my transit.
 
#7 · (Edited)
You guys may be ovethinking all this. You are certainly making my head swim...
Certainly not the first time I've been guilty of that! ;)
Rick I thought you had Navionics or any other program since you have your computer at the helm. It tell you tide and currents and vector arrows direction at specific spots along the way or even at your location...
Yes, I use OpenCPN both at home and at the helm. It's a fantastic tool, and predicts both tide levels and currents at all the NOAA sensors just by right-clicking on the chart. However, it defaults to showing a graph for the present day. In order to bring up the tidal current graph for a day 4 months in the future, I need to click the "Next" button ~120 times. And I need to redo that every time I bring up a different graph. (Maybe a different commercial package would do this better, but OpenCPN works perfectly for almost everything else that I do.) So the old fashioned current tables, whether Eldridge or NOAA, are the best thing I have right now for future planning.

As I already mentioned, this whole thing is a learning process for me, but one that is worth it because I expect to be making a lot more transits through the canal going forward, and the lunar calendar is rather predictable so I can leverage what I learn for many future trips.

...I know how to figure out with Eldridge and all, but in todays world where I know you are comptuer savy there is an easier more efficient less time consuming way.
Any route on the Delaware that lasts less than 5 hours is pretty simple to predict - just time it to stay in the favorable current. But when you go out for more then 5 hours (downriver) or 7 hours (upriver), planning becomes more difficult because you'll encounter a tidal swing during your trip. And turning into the canal makes it even more complicated because its ebb and flood are on a different timetable than Chesapeake or Delaware. That's why you (Dave) have to stop at Reedy Point every time on your way to the ocean, and why I suggested stopping off heading from Philly to Chesapeake. As you've noted before, going the opposite direction (ocean to Baltimore or Chesapeake to Philly) can be timed to proceed without a delay at the eastern end of the canal because the currents at the canal entrance are in sync with the river currents in that direction.

That complication is the reason I cobbled together a spreadsheet planning tool for the Philly-Chesapeake. I haven't seen another tool that does this.
 
#11 ·
Certainly not the first time I've been guilty of that! ;)

Yes, I use OpenCPN both at home and at the helm. It's a fantastic tool, and predicts both tide levels and currents at all the NOAA sensors just by right-clicking on the chart. However, it defaults to showing a graph for the present day. In order to bring up the tidal current graph for a day 4 months in the future, I need to click the "Next" button ~120 times. And I need to redo that every time I bring up a different graph. (Maybe a different commercial package would do this better, but OpenCPN works perfectly for almost everything else that I do.) So the old fashioned current tables, whether Eldridge or NOAA, are the best thing I have right now for future planning.

As I already mentioned, this whole thing is a learning process for me, but one that is worth it because I expect to be making a lot more transits through the canal going forward, and the lunar calendar is rather predictable so I can leverage what I learn for many future trips.

Any route on the Delaware that lasts less than 5 hours is pretty simple to predict - just time it to stay in the favorable current. But when you go out for more then 5 hours (downriver) or 7 hours (upriver), planning becomes more difficult because you'll encounter a tidal swing during your trip. And turning into the canal makes it even more complicated because its ebb and flood are on a different timetable than Chesapeake or Delaware. That's why you (Dave) have to stop at Reedy Point every time on your way to the ocean, and why I suggested stopping off heading from Philly to Chesapeake. As you've noted before, going the opposite direction (ocean to Baltimore or Chesapeake to Philly) can be timed to proceed without a delay at the eastern end of the canal because the currents at the canal entrance are in sync with the river currents in that direction.

That complication is the reason I cobbled together a spreadsheet planning tool for the Philly-Chesapeake. I haven't seen another tool that does this.
My best was last year actually. We left Cape May 1.5 hours before max Ebb at the CM Canal entrance and flew up the Delaware at 8.5 SOG, hit the tide perfect going through the canal all the way to Still Pond going 8+ again. We still had 5 hgours of dayilight so we booked for our dock in Rock Creek

As we got to the Patapsco we were chased by a waterspout comming off the land between Dundalk and Middle River. Cared the **** out of me as it was 1/2 mile behind us, but was moving east. The whole trip took 14 hours from Cape May ( Utsches) to our slip. Our best was Worton Creek before, but daylight, tides, wind a current lined up this time

Rick,

As far as fighting current, it is ineveiable if you are going to sail on the Delaware., A prime reason for moving to the Chessie:), plus think of the other achoring alternatives it will open up for you. To me a one hour ride in the car is worth fighting currents and tide changes which make you waste more than that in the big pitcure. I am waiting for the day you tell me you have decided to join us permanently:) I see it in your future as you guys move forward.

A couple hours fighting the tide wont hurt you too bad ( Colin it will because of his boat speed). I woul go into Chesapeake City before going down to Reedy and backtracking. But if you are coming from the south usually you can ride the tide up the Delaware through the Canal as james and rich have said.
 
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#9 ·
Rich
The max current on June 12th is 2.5, but on the evening of June 7 it is 1.5

On the Delaware River our maximum flooding from up state NY is usualy in the spring and at Essington may add another 2 ft to high tide, enough to still impact the flow at the C&D. Sandy produced an extra 3ft, at Essington but did not top the seawall 3ft above high high at Delaware City, it would have been a lot worse if Sandy had tracked over the Delaware Bay or if the watershed above Trenton had a rain event.

I have been in 3 knot opposing current approach the Chesapeake City Bridge from the Chesapeake which droped my speed from 4 to1 for about 30 mins, not something I would like to repeat but it was for a finite time.
 
#12 ·
Timely discussion. I'm looking to sail around DelMarVa this year, and have been wondering how to time my passage through the C&D canal.

I'm looking to make a counter-clockwise trip, so I'll be hitting the C&D from the East, motoring West. James W. has been a big help with planning.

My engine runs very well, but I'm not interested in stressing it out. I hope I don't have to run at WOT for long periods in order to time the currents.
 
#23 ·
Bubble,

If you leave Cape May/ Cape Henlopen 2 hours before maximum ebb you will make it through the Canal to at least the Northeast/ Sassafras River riding the tide all the way. When are you thinking of doing this? ( date) I can give you more specific data.,
 
#13 · (Edited)
Even though I had 10-15 knots out of the ESE, I motorsailed the most of the way up the Delaware Bay and Delaware River to the C&D, so I could make the 8 knots over the ground necessary to ride the current for 14 hours. The difference was the boat never slowed down, so the P28 would hit 8.5 knots surfing down the front of the chop and not slow down to 5 knots on the back.

You can hear the engine running (and my rudder clicking) in the video, while I sail at maximum speed:
 
#14 ·
Even though I had 10-15 knots out of the ESE, I motorsailed the most of the way up the Delaware Bay and Delaware River to the C&D, so I could make the 8 knots over the ground necessary to ride the current for 14 hours. The difference was the boat never slowed down, so the P28 would hit 8.5 knots surfing down the front of the chop and not slow down to 5 knots on the back.

You can hear the engine running (and my rudder clicking) in the video, while I sail at maximum speed: Glorious day on the Delaware Bay... - YouTube
James,

I'm curious about the dinghy shown in your video. Is it a soft inflatable bottom, or hard bottom? How heavy is it? Have you ever had it flip on you? Do you do anything special to prevent flipping in rough seas?

My little cheapo dinghy (shown in my profile pic) was purchased on short notice just to have something on last year's Chesapeake charter. It weighs about 50 lb and stores in a bag. I have never used it - just the leak test in my living room (shown in the pic).

When I got it, it was a little better quality than I expected. It is just PVC (not Hypalon, like the better dinghies), but it is multi-ply, with a very nice nylon fabric sandwiched between the plies that prevents stretch and allows it to become very rigid when pressurized. It might actually be a viable dinghy for towing behind the boat. But I'm concerned about its light weight, and the possibility of it flipping.

Design-wise, it looks similar to your own dinghy, so I'm curious about your towing experience with it.
 
#15 ·
Just to add to the confusion a little.

I'm working on the planning for a possible June 2013 transit to NE including the C&D/Del Bay transit. The currents shown in Garmin BlueChart mobile and on the NOAA current tables don't match up.

Here's an example

June 1, 2013 for Reedy Pt, DE

Max flood Slack Max Ebb
Garmin 03:11 06:39 11:10
NOAA 04:49 07:35 11:49

Any ideas on what might cause the differences?
 
#16 · (Edited)
paperbird
Look further back in this thread or the one this migrated from, TakeFive references the differences between various gauge station for the C&D.

At the Delaware end there are at least 3 stations; at the radio tower east of the route 9 bridge, on the jetty end (Reedy Point) and 1.1 miles east of the jetty end.

From Delaware bay as noted by others it is possible to time your transit with the current from bay through canal.

Going canal to bay usualy requires waiting for a favorable current down the Delaware.

Transiting from the Delaware River with the current above the canal then through the canal will require either waiting for a favorable canal current or transiting against the current for some time.
 
#18 ·
Thanks Ulladh,

But those readings are for the exact same stations (by name and lat/lon) just different sources. That's what's troubling me a little. Maybe it's the source data used by Garmin?

After looking at it for a bit, I agree that going from the C to the D ideally requires riding the current through the Canal then stopping and waiting for the current to turn in the Delaware. In June, the assist (or opposition) from the current will be between 2 and 3 kts the entire 60ish mile trip to Cape May.

Of course, that all assumes the wind is either light or NOT southerly. All bets off if the wind is against the current out there.
 
#20 ·
Tide and currents predictions are based on historical data most of which is produced by NOAA from their various stations.

It would be interesting to compare actual conditions experienced in the canal next to one of the stations (say radio tower at route 9 bridge), with real time data from the station and predictions from the tables. Only a snap shot but it could give a tolerance range maybe plus or minus 30 min or more for the predictions.
 
#21 ·
I disagree with the suggestion that NOAA's tidal current prediction are based strictly on modeling. I always believed that their multi-harmonic models were tweaked based on the hundreds of sensors that they have. And until someone provides proof to the contrary, that's what I'll continue to believe.

If there are discrepancies between Eldridge, Garmin, NOAA, or others, I assume that it's because they update their models based on different weighting factors. It's the classic case of separating "trends" from "noise," and it will cause differing predictions, much like the weather. Over time you may decide to have more confidence in one than the other.

Recommended reading: Tidal Current Predictions and Data

C&D Canal is a perfect example of hydraulic current.

The Delaware river exhibits something between progressive wave and standing wave, depending on location. Up near Philly where I sail most of the time, slack typically lags high and low tide by about an hour. The progressive wave model explains why you can have a flood current even after high tide has passed. If you've ever stood in waist deep water at the beach and felt a wave pass you, you've observed a progressive wave. Right after the wave passes, the water level drops, but the surface continues to push you in toward shore, while the strong undertoe starts to pull you out. Similar things happen in rivers - high tide is a wave that moves up the river, but its wavelength is so long that you can't really see it aside from observing the changing tide height along pilings, seawall, etc.
 
#22 ·
BTW - the differences persist up and down the Delaware Bay, well outside the unique influences of the C&D canal.

I've posted a note with Garmins tech support team and will let folks know what they say. I suspect it'll be related to either their source data or their underlying model.

In any event, this is a classic example of why the prudent navigator will look to many sources, not just one. So carry a copy of Eldridge, print out NOAA, use Garmin and compare to what you see with your own eyes.
 
#29 · (Edited)
...I've posted a note with Garmins tech support team and will let folks know what they say. I suspect it'll be related to either their source data or their underlying model...
Please let us know what they say - it will be interesting to see what they are willing to tell you. I have the Bluechart mobile on an iPad at home, so I just looked at its current predictions. It's still so new that it hasn't become my go-to device (I still use OpenCPN for mostly everything), so I'm just learning.

NOAA's multi-harmonic model is very sophisticated (I read somewhere that it uses over 12 harmonics), and the source code can be purchased from them for a fee. Despite what some may believe, it is based on what I believe to be the world's most extensive collection of historical data for US waters. That historical data is available openly, and companies like Garmin almost certainly use the same data in developing their own models.

Unfortunately, much of the tidal modeling that used to be freely available for use has been tied up by private companies (like Garmin) making intellectual property claims, so unfortunately there will never be a convergence to a "single best" prediction (unless you believe that nobody can top NOAA's brainpower, which unfortunately has become as much an ideological question as a scientific one). But it's almost certain that everyone uses the same NOAA data (though different companies may update their models for recent data more or less frequently). So the main difference is probably the model that's used to fit the data and make future predictions. There are some interesting comments on the difficulties of doing this here on the XTide support page.

I took a quick look at Garmin's current predictions on the iPad, and the waveforms look very sinusoidal, which is a signal that they use fewer harmonics in their predictions than others. So in general, it may be less precise than models with more harmonics, although there is a valid question of how precise anybody's prediction can be because the effects of rain, wind, and other less predictable effects would limit the precision of any model, no matter how sophisticated. At some point your prediction becomes far more precise than Mother Nature is willing to cooperate with. ;)

FYI, OpenCPN has some very complex wave shapes in both their tide and current predictions, which is a sign that their predictions (based on the XTide algorithms, but with significant manual tweaking) incorporate a lot more harmonics than Garmin's. Once again, whether that actually leads to a better prediction is up for debate.

In addition to the XTide support site, there is also some very interesting background information on tide/current predictions on NOAA's site here. For instance, the lower harmonics are such a low frequency that you need 18.6 years of tidal data to make a reliable prediction. This is not something that you can do by flipping through a few pages of data and manually fitting a spline curve!

By the way, click here for a fascinating rant on how privatization and "un-public-domaining" of tidal data has made it virtually impossible for anyone to offer free tidal predictions in Europe.
 
#25 ·
I've reached almost exactly the same timetable you've laid out, Chef. Sneak out of work on Friday (work by phone) and meander up the Bay, through the C&D to behind Reedy Island. Then catch the dawn tide shift to ride it through the Delaware.

I've done the Delaware at night and it's not my favorite. Although it'll be a waxing 1/2 moon around the beginning of June.

Yeah - I'm not too worried about powering hard if we need to. In fact, I would be OK bucking the current for a slow ride through the Canal at night if need be to catch the ride down the Delaware at first light.

The huge unknown, of course, is the wind. And no way to know that until June comes. I'm plotting out the departure times for all the weekends in June figuring that one of them will offer a good weather window.
 
#26 ·
I've reached almost exactly the same timetable you've laid out, Chef. Sneak out of work on Friday (work by phone) and meander up the Bay, through the C&D to behind Reedy Island. Then catch the dawn tide shift to ride it through the Delaware.

I've done the Delaware at night and it's not my favorite. Although it'll be a waxing 1/2 moon around the beginning of June.

Yeah - I'm not too worried about powering hard if we need to. In fact, I would be OK bucking the current for a slow ride through the Canal at night if need be to catch the ride down the Delaware at first light.

The huge unknown, of course, is the wind. And no way to know that until June comes. I'm plotting out the departure times for all the weekends in June figuring that one of them will offer a good weather window.
Good show,

Weve done this trip about 40 times...The most boring part of heading north. Taking the morning tide usually means calm water in the AM down in the Bay before the onshore breeze starts cranking in and builds up the chop.

The canals not bad at night, but the Delaware is not my favorite as there can be floating objects

Where are you going in NE?. brokersailor is headed nborth in mid June I think. Where do you sail from. Are you stopping in Cape May?

We wont be heading up till mid August as we like no crowds and theres no wind here in the Chessie usually.

dave
 
#28 ·
Just can't get enough, huh? Tentative plans are early to mid-June. Don't know brokesailor - will have to look him up.

We live in Annapolis, but keep the boat at Herrington North. Have done the round trip once as a family. But also the North-then-West one way a couple times. Last time we stopped in Cape May for a night's sleep, but we had 3 weeks for the trip. This time we may be limited to 2 weeks so am considering not stopping. Our air draft (53') is cutting it close for the Cape May Canal anyway. If we have to go around, then I'm inclined to just keep going for Block.

Funny story - when we came through the canal at night, I was asleep below and my wife was on watch. She yelled that a big ship with a strange light configuration - 2 whites in a horizontal line - was heading right towards us really, really fast! Turned out to be a truck driving on the access road next to the canal. But a serious enough adrenaline shot that she was very alert the rest of her watch.
 
#31 ·
Just can't get enough, huh? Tentative plans are early to mid-June. Don't know brokesailor - will have to look him up.

We live in Annapolis, but keep the boat at Herrington North. Have done the round trip once as a family. But also the North-then-West one way a couple times. Last time we stopped in Cape May for a night's sleep, but we had 3 weeks for the trip. This time we may be limited to 2 weeks so am considering not stopping. Our air draft (53') is cutting it close for the Cape May Canal anyway. If we have to go around, then I'm inclined to just keep going for Block.

Funny story - when we came through the canal at night, I was asleep below and my wife was on watch. She yelled that a big ship with a strange light configuration - 2 whites in a horizontal line - was heading right towards us really, really fast! Turned out to be a truck driving on the access road next to the canal. But a serious enough adrenaline shot that she was very alert the rest of her watch.
We are also 53 ft and have never had trouble in the Cape May Canal. Just make sure its not a full moon and high tide.

We go north every year for at least 21/2 to 3 weeks, We do stop at Utsches before heading up the coast.

I have been in the C&C Canal once at night when we saw a big ship ( lights and radar) and pulled to the side. There was a 35 ft sailboiat following us a half mile back who stayed in the center. The freighter blew his horn at 10PM right next to us and we almost jumped out of the boat.

I have seen the lights of truck and they are confusing although those yellow vapor arc lights of the canal are bright.

dave
 
#38 ·
Dark out going top speed of 30 in the Canal on autopilot.....and thats all the damage from hitting the rocks. I have seen 3 side of the boat in pictures and it looks like nothing. 30 mph and it only goes a little on the rocks

Something wrong with these facts.
 
#39 ·
Since my friend pieced together the story from informal comments he heard from bystanders at the scene, it is very possible that facts are wrong or exaggerated.

However, do realize that the guy did not run head-on into the rocks. He veered over gradually into them.

My friend personally saw that boat on the hard at Summit North, and there was extensive damage to the part of the hull that you can't see in the pictures (because it's lying on the rocks). They had to attach a large sheet to patch over the hole so the boat could be towed without sinking. That's one of the reasons they had to wait until the next day to refloat.
 
#46 ·
Just to add to the complex predictions for tide/current at the C&D.

Yesterday 2/1/2013 the observed high and low at Reedy Point was 2ft below predicted high and low water levels.
 
#47 ·
Similarly in Marcus Hook and Philly. My assumption is that the 20-30 kt NW winds blew the water out of the bay, and that effect drained the river upstream from the bay.

On the subject of C&D currents, I stumbled across this nice explanation of how to best time your passage. I haven't had time to calculate how it might change for our slower boats:

Chesapeake and Delaware Canal - Timing Your Passage
 
#49 ·
Yes, see how the timing works out. As I mentioned before, it might actually be better to do Cohansey to Delaware City (as you originally suggested), then on Sunday do a two-way trip to Chesapeake City for lunch and walking around town. We could all go for the day on one boat, or if you preferred to stay in Delaware City we could go ourselves and meet you back at Delaware City in the evening. I'm flexible on this, and the currents look like they might be running perfectly on Sunday for the two-way trip.
 
#51 ·
Skip Smith Island and Tangier. You can take a ferry to either island from the shore for a day excursion. Tangier is nice, quaint and underwhelming. There are submerged hazards in the area and it puts you in an undesirable part of the Bay for fast North-South travel. I would stick to the Western shore in that part of the Bay and jump from the Great Wicomico (or parts south) to Solomons Island (or parts north) or vice versa. Fleet Bay has some beautiful anchorages as well.

There is such a long stretch without good anchorages North from Solomons (except Little Choptank) and a long day's sail from Great Wicomico to the mouth of the Bay, where you can anchor at Cape Charles or Kiptopeake for the Northern Channel, that I would not stop anywhere in the vicinity of the mouth of the Potomac. I love the area for daysailing, but it is less than ideal for anything other than leisurely local cruising or travel.
 
#53 ·
Further, I love Cape May, N.J., and would spend as much time there as possible, however, if you really want to make a fast Delmarva circumnavigation, stop at the breakwater in Lewes instead of crossing the Delaware Bay and head up from there.
I'm trying to talk my wife into taking our little boat down the Delaware River to Cape May for a week-long trip (this year or next year). If we time things right, I'm hoping to go two days each direction from Essington (stop off in Cohansey), and a few nights in Cape May. I assume Utsch's is the place to stay, right? Other recommendations?
 
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#57 ·
Utsches are friends of mine. We stop there twice every year. Nice restaurants close and town is a mile walk or a ten dollar cab ride. Nice ACME in town for provisions, Lots of great restaurants shops etc, Chance to go out into the Ocean for a few day sails or do Atlantic City which is 30 miles north, as CM inlet is easy although a combo of the Indy 500 and NHRA Winternationals.
You could make it from Essington in one long day and definately could go through the CM Canal at 55 ft max.

Dave
 
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