C & D Canal - Timing Your Passage
Since most of us can appreciate a fair current push to help us along our way, how do we determine the best times to make the Chesapeake and Delaware Canal passage?
For those of you that are just looking for the numbers, we will get them out of the way now:
- An eastbound vessel entering the canal at 3 minutes before "Slack Water Flood Begins" at the Chesapeake City Reference Station will catch the very beginning of a fair current push.
- A westbound vessel should enter the canal about 7 minutes before "Slack Water Ebb Begins" at the Chesapeake City Reference Station to catch the very beginning of a westbound fair current.
Determining When a Fair Current Begins
We will be using the NOAA Tidal Current Tables; you must correct for DST when necessary. For those that prefer you can use Eldridge. Simply look up the C & D canal in "Table #1" and extract the time of "Slack Water Flood" (eastbound vessels) or "Slack Water Ebb" (westbound vessels) at the Chesapeake and Delaware Canal reference station, in this case Chesapeake City, MD. From "Table #2", extract the time corrections for the proper substation, and apply this correction to determine the correct time for slack water.
For our example we will use the NOAA Current Tables and compute the times for the first favorable current of the day on January 1st 2011.
|C & D Canal Fair Current Timing|
|Eastbound||Slack Water Flood Begins|
|Chesapeake City ( Table #1)||0052|
|"Back Creek" Table 2 corrections||-0003|
|Back Creek (Slack Water Flood Begins)||0049|
In the table above we are transiting the C & D Canal eastbound from the Upper Chesapeake to the Delaware River. So we need to find out what time we should be at the western entrance of the canal to catch a fair current. We know that the current floods eastbound in the C & D so we will be looking for the first flood current of the day.
- Enter Table #1 of the NOAA current tables for the C & D Canal and for the selected day extract the time of the first "Slack Water Flood Begins". In this case it would be (0052).
- Now Enter Table #2 of the NOAA current tables for the C & D Canal and locate the sub-station at the western end of the canal, in this case "Back Creek," and extract the time correction for "Minimum Before Flood" (-0003).
- Apply the correction to the 0052 obtained from table #1 and you will have the time that slack water flood begins (0049) and a fair current push at the western entrance to the canal.
For a westbound passage we simply repeat the process using "Slack Water Ebb," since the current ebbs to the west, and use the sub-station at the eastern entrance to the canal, "Reedy Point". (See below)
|C & D Canal Fair Current Timing|
Slack Water Ebb Begins
|Chesapeake City ( Table #1)||0647|
|"Reedy Point Tower" Table 2 corrections||-0007|
|Reedy Point (Tower) (Slack Water Ebb Begins)||0640|
On average, a 7 knot vessel will have a about a 3½ hour window from the time of slack water to make the passage and still have a fair current the length of the canal. A higher speed vessel will have an even larger window.
How long will it take me to get through the canal?
There are 2 ways to approach this problem the "right way" and the "other way." Let's take a look at the "right way":
- Beginning at the entrance to the canal at a specific time, you must first compute the actual velocity of the current for that time.
- Using the NOAA Tidal Current Tables, enter "Table 2" and locate your 1st station. Using the differences and ratios shown, calculate the times of Slack Water, Maximum Current Time (Flood or Ebb),and Current Velocity for the times immediately preceding and following your ETA at that station
- Determine the time interval between slack water and the maximum current for the time bracketing the time of your arrival.
- Determine the time interval between slack water and the time of your arrival at the location above.
- Enter "Table B" at the intersection of the closest times to those that you have determined in steps b. and c. and extract the current factor listed.
- Apply this factor to the maximum current speed to arrive at the current velocity for the time you specified.
- e. Apply this current velocity to your cruising speed and using T=D/S compute your ETA to the next station.
- Using this ETA, repeat this process for the next station, and that ETA for the next until you have done the calculations for all 5 stations in the canal.
What about the "other way" you ask?
- Determine the overall average current velocity for the canal.
- Apply this current to your cruising speed.
- Use T=D/S to compute the time required to transit the canal and your ETA.
The "right way" will provide you with improved accuracy, but the 2 things to consider here are:
- The tidal current predictions are only 90% accurate to within 30 minutes to begin with. and
- What happens if you miss your timing to the first waypoint and you have to start the whole process over again.
It may be just me, but I am seriously into "the other way!"
In an effort to keep it simple we have done some of the calculations for you (to 1 decimal place). Using the NOAA Tidal Current Tables #2 we extract the average maximum current velocity for the Reference Station as well as all of the Sub-Stations located in the C & D Canal and then take the average.
|C&D Canal Average Maximum Current Velocities|
|Current Station||Ebb Current Avg. Maximum||Flood Current Avg. Maximum|
|Back Creek||1.4 knots||1.2 knots|
|Chesapeake City (Ref. Sta.)||1.9 knots||2.1 knots|
|Chesapeake City Bridge||1.4 knots||2.0 knots|
|Conrail Bridge||1.3 knots||1.9 knots|
|St. Georges Bridge||1.3 knots||1.7 knots|
|Reedy Point Bridge*||2.1 knots||2.6 knots|
|Reedy Point Tower||1.4 knots||1.2 knots|
|Canal Average||Ebb Current 1.5 knots||Flood Current 1.9 knots|
|*Reported by Coast Pilot #3 Chapter 7|
Keep in mind that this is the maximum average current speed, if you are of a more conservative nature you may want to modify this number and use that result for your calculations.
With the known distance of the C & D Canal (15.3 NM), the average current velocity, and our intended cruising speed, we can now calculate the time required to transit.At 10 knots cruising speed (±) the average current velocity will give you your estimated SOG. Then dividing the distance by your SOG will tell you how long it will take to make the passage through the C & D.
So if we are westbound facing a foul current (floods east) for instance, simply take your cruising speed (10 knots) and subtract the average current speed (1.9 knots) giving you a SOG of 8.1 knots. Dividing the distance (15.3 NM) by this SOG will result in the time required to pass through the C & D Canal; about 1 hour and 53 minutes. If you waited for a fair current the same passage would only require 1 hour 19 minutes saving you 34 minutes of traveling time. A 7 knot boat would save almost 1¼ hours.
You’ve Made It This Far
For those that have stuck around this far and have read this whole thing, you deserve something for your perseverance. So here is an extra we hope you will find useful.
We have talked about the timing to get through the canal with a fair current. The problem is that very few people transit the C & D Canal just to get to the other end. Most seem to have some other destination in mind. Don't get me wrong, I do not mean to imply that oil refineries, nuclear plants, and spoil areas aren’t visually appealing, it just seems to me that most cruisers have something else in mind.
For an eastbound 7 knot vessel bound north on the Delaware River you will want to enter the C & D canal at Back Creek about 1 hour and 16 minutes (±10 minutes) after slack water flood begins at Chesapeake City. This will provide you with a fair current thru the canal and put you in the shipping channel of the Delaware River just as Slack water flood begins off of Reedy point. This should give you about 6 hours of fair current inbound on the Delaware River.
Regretfully, there is no grand solution if you are southbound for the Delaware Capes or Cape May with a low powered vessel. You will have to decide whether to battle a foul current in the C & D or fight the fight when you are outbound the Delaware. The obvious choice, at least to me, would be to take advantage of the 1 to 2 knot push in the Upper Delaware for the trip to the Capes. Even so, a 7 knot boat will likely run out of the fair current in the vicinity of Miah Maull Light. At 15 knots however, you should be able to make the entire transit to the capes with a fair current. To make best use of this, a 7 knot vessel will want to enter the C & D eastbound approximately 37 minutes after slack water ebb begins at Chesapeake City or 2 hours and 56 minutes before slack water ebb begins in the shipping channel off of Reedy Point.
Vessels westbound for Baltimore should enter the C & D Canal approximately 7 Minutes before slack water ebb begins at Chesapeake City. A 10 knot boat will typically carry a fair current all the way to Baltimore while a 7 knot vessel will likely lose the fair current in the vicinity of Pooles Island.