Crossing the Spitway 2025

[MattS]

Is this still the latest survey of the Spitway (from 2024) https://www.crossingthethamesestuary.com/Spitway 2024 Download V3.pdf?

I've 'lost' (leant to someone and forgotten who) my copy of CTTE... can someone remind me which tidal port as best reference for Spitway depths?

Am hoping to cross from Swin to Wallet this Friday evening heading into Brightlingsea and trying to work out timings for required depth (draft: 1.7m)

Thanks!

 

[tillergirl]

Walton:

Tidal information

You can effectively treat the Walton HoT as the Spitway. Obviosuly the Spitway is later than Walton so there would be less HoT BU, the range is bigger so it kinda balances the time difference. I haven't redone it this year yet but when we went through to the SW Sunk everything seemed to be 'unremarkable' and other users have commented ditto. Slightly better water to the East as shown on the downlaod: Downloads (second item).

If you can get data on line while afloat you can get the PLA live data on the Walton gauge. If not use the PLA predicted tide heights below (this for the 11th). (NB the predicted heights are GMT but the live data is BST!

HOUR	00	10	20	30	40	50
00	2.53	2.42	2.31	2.21	2.11	2.01
01	1.92	1.83	1.75	1.67	1.60	1.54
02	1.48	1.42	1.37	1.33	1.30	1.27
03	1.26	1.25	1.26	1.28	1.30	1.34
04	1.39	1.45	1.51	1.58	1.65	1.73
05	1.82	1.91	2.00	2.11	2.21	2.33
06	2.44	2.56	2.69	2.81	2.93	3.05
07	3.16	3.27	3.37	3.47	3.56	3.64
08	3.72	3.79	3.86	3.91	3.96	4.00
09	4.04	4.06	4.07	4.06	4.05	4.03
10	3.99	3.95	3.90	3.83	3.76	3.68
11	3.60	3.51	3.41	3.31	3.20	3.09
12	2.97	2.86	2.74	2.63	2.51	2.41
13	2.30	2.21	2.11	2.03	1.95	1.87
14	1.80	1.73	1.67	1.61	1.56	1.51
15	1.47	1.44	1.41	1.39	1.38	1.38
16	1.40	1.42	1.45	1.49	1.54	1.59
17	1.65	1.72	1.80	1.88	1.97	2.07
18	2.17	2.28	2.40	2.52	2.64	2.77
19	2.89	3.01	3.13	3.24	3.35	3.45
20	3.54	3.64	3.72	3.80	3.86	3.93
21	3.98	4.02	4.05	4.07	4.08	4.08
22	4.07	4.05	4.02	3.97	3.92	3.86
23	3.79	3.71	3.62	3.53	3.43	3.32

Data courtesy of the Port of London Authority

with a draft of 1.7, the lowest Walton HoT is predicted 1.28m (am) and 1.38 (pm). Light winds predicted.

 

[MattS]

Thanks @tillergirl

What's "BU" sorry?

less HoT BU

Also, struggling to make the table you have pasted above match my own tide tables for Walton-on-the-naze on Friday? Mine seem to suggest lowest Walton HoT on Friday 11th is 0.9 (0546 UTC) and 0.7 (1817 UTC).

What am I missing?

 

[tillergirl]

That's a blunder! 'BUT'

I read of the Walton from the PLA prediction. It does look odd. We are looking the am at West Mersea at 0735 1.1. I'll go back to the PLA website.

 

[tillergirl]

This is better

HOUR	00	10	20	30	40	50
00	3.93	3.88	3.82	3.74	3.64	3.54
01	3.43	3.31	3.19	3.07	2.94	2.82
02	2.69	2.57	2.46	2.34	2.24	2.13
03	2.03	1.94	1.84	1.75	1.66	1.57
04	1.49	1.40	1.32	1.25	1.18	1.12
05	1.07	1.02	0.99	0.97	0.95	0.95
06	0.96	0.98	1.02	1.06	1.12	1.19
07	1.27	1.35	1.44	1.53	1.63	1.72
08	1.82	1.91	2.01	2.10	2.20	2.30
09	2.40	2.51	2.62	2.73	2.84	2.96
10	3.07	3.18	3.29	3.41	3.51	3.62
11	3.72	3.81	3.88	3.95	4.00	4.03
12	4.03	4.02	3.99	3.94	3.87	3.78
13	3.69	3.58	3.46	3.33	3.19	3.06
14	2.92	2.78	2.65	2.52	2.39	2.27
15	2.16	2.05	1.94	1.84	1.74	1.65
16	1.55	1.46	1.37	1.28	1.19	1.11
17	1.03	0.96	0.89	0.84	0.79	0.75
18	0.73	0.71	0.71	0.72	0.74	0.78
19	0.82	0.87	0.94	1.01	1.09	1.18
20	1.27	1.36	1.45	1.55	1.65	1.75
21	1.86	1.97	2.09	2.21	2.33	2.46
22	2.59	2.72	2.86	2.99	3.13	3.26
23	3.40	3.53	3.65	3.76	3.86	3.94

Not sure what happened. When I went back to the page, I flicked it to the Tidal Curve and whilst it displayed Walton, running the cursor over the curve it displayed 'Margate'. I then went to the Margate prediction, flashed back to the Walton prediction and got the above! I claim I am innocent and I shall tell the PLA.

PS: Fortunately I saved the screenshots. There is a glitch on the predictions so I can alert the PLA. But those here are for Walton on 11th.

 

[MattS]

@tillergirl Does sound like some strange website behaviour to me...

Could I just clarify then - you would expect lowest HoT at the spitway to be less than lowest HoT at Walton - correct?

Just struggling to understand this sentence a little:

Obviosuly the Spitway is later than Walton so there would be less HoT BU, the range is bigger so it kinda balances the time difference.

 

[johnalison]

Whatever the predictions, my general rule is that there is invariably half a metre less than I was expecting. Doing the Spitway at near springs is always a nuisance unless you have shallow draft. Being somewhat wimpish about these things I would be aiming to buck the tide and get there a couple of hours after low and take the tide into Brightlingsea, where you probably wouldn't get in at LW anyway.

 

[MattS]

Whatever the predictions, my general rule is that there is invariably half a metre less than I was expecting. Doing the Spitway at near springs is always a nuisance unless you have shallow draft. Being somewhat wimpish about these things I would be aiming to buck the tide and get there a couple of hours after low and take the tide into Brightlingsea, where you probably wouldn't get in at LW anyway.

Thanks John - and agree. This is my current plan - aim to arrive at the spitway when there is enough water on the rising tide, and as you say crossing the spitway on the falling tide is going to put me at Brightlingsea a couple of hours before I can likely get into the harbour anyway.

Half a metre less than Walton HoT is a good enough ballpark for me, and let's me work out a plan combined with Roger's advice above

(This is not my first time across the spitway, however it is my first time in a vessel without a 1.1m bilge keel!)

 

[Malish]

I use the Whitaker Beacon as a secondary port on the Absolute Tides app, that gives a minimum depth of 0.7m @ 19.50 on Friday and your chartlet gives a min depth of 1.7 to the NE of the safe water buoys. Unless it is bouncy on Friday I would cross at LW (with a little caution).

 

[MattS]

I use the Whitaker Beacon as a secondary port on the Absolute Tides app

Thanks - I did wonder about that, but it shows a higher HoT than both Brightlingsea and Walton (1.1m) on the morning HW, so was a bit nervous about relying on that. Both Brightlingsea and Walton HoTs seem to be the same on Friday.

I should think that John's rule of 0.5m under the listed HoT for the spitway could probably be used for Whitaker Beacon as well to play things safe, given there is only a small difference between all three ports...

 

[tillergirl]

I have sent off an email to the PLA. I suspect it might take a little while for the web makers to find the issue. I think anybody using the prediction pages at the moment should select the pdf output.

LW springs at the Spitway is 30 minutes later than Walton so at 0730 GMT is 1.53m but 30 minutes earlier is 1.27m. But the range at the Spitway is 1.12 on springs. 1.27 x 1.12 = 1.42 e.g. theoretical HoT at the Spitway at 0730 GMT. E.G. the Spitway is 0.1m less at Walton. To confuse the issue I have looked up the data for the 2024 survey. At 1005 BST there was a predicted HoT of 1.34m whereas there was an actual HoT of 1.6m - almost nine and a half inches extra! If you don't have the interweb while aflaot (I don't), London VTS does broadcast Walton's HoT 15 minutes before and after the hour on channel 69. Indeed you could always call up VTS for the HoT at Walton. I have always found them very helpful.

I have just tried to upload the Brightlingsea entrance chartlet but it is too large. Later tonight I may be able reduce it's file size.

 

[John_Silver]

Thanks - I did wonder about that, but it shows a higher HoT than both Brightlingsea and Walton (1.1m) on the morning HW, so was a bit nervous about relying on that. Both Brightlingsea and Walton HoTs seem to be the same on Friday.

I should think that John's rule of 0.5m under the listed HoT for the spitway could probably be used for Whitaker Beacon as well to play things safe, given there is only a small difference between all three ports...

Using the Navionics rise of tide, at the Whittaker; with a 1.8m keel; and following @tillergirl ‘s survey / waypoints for best depth through the Spitway: I reckon on Whittaker rise +0.4m, for clearance under the keel - based on logged actuals.

 

[MattS]

Using the Navionics rise of tide, at the Whittaker; with a 1.8m keel; and following @tillergirl ‘s survey / waypoints for best depth through the Spitway: I reckon on Whittaker rise +0.4m, for clearance under the keel - based on logged actuals.

Hi @John_Silver - do you mean clearance under the keel will be at +0.4m after lowest tide at Whittaker?

 

[John_Silver]

Hi @John_Silver - do you mean clearance under the keel will be at +0.4m after lowest tide at Whittaker?

Badly put. Take 2:
With a 1.8m draft, and following tillergirl’s recommended line, the clearance beneath the keel is 0.4m more than the rise of tide, shown on Navionics, for the Whitaker, in the Spitway.

 

[MattS]

Badly put. Take 2:
With a 1.8m draft, and following tillergirl’s recommended line, the clearance beneath the keel is 0.4m more than the rise of tide, shown on Navionics, for the Whitaker, in the Spitway.

Ah - I think I understand - but if I'm still way off then feel free to give up on me!

Navionics showing 0.6m lowest HoT at Whitaker on Friday 11th, Spitway chartlet shows 1.6m as shallowest depth - therefore with (0.6+1.6 = 2.2m) of water, there will be 0.4m of water under a 1.8m draft keel

 

[John_Silver]

I’m not phrasing this well…..

With 0.6m rise of tide @ Whitaker + 0.4m = 1m least depth under keel in the Spitway.

Last time I went through, the log says the Whitaker rise was 0.6. And, coming up to the Swin waypoint, least depth was 1.0. (Beneath a 1.8m keel, following tillergirl’s line. Between the two safe water marks I subtract 0.1m, from the Whitaker rise)

 

[Daydream believer]

I am confused
Can someone explain how to use that PLA table please

 

[tillergirl]

PLEASE, PLEASE, DO NOT RELY ON NAVIONICS AT THE SPITWAY. Of course you all know I am an amateur so by all means ignore the CTTE download. But if you want the latest data, all go and buy a copy of UKHO SN Chart 1975 (POD). If you are trying to rely on Navionics on the south side of the Estuary, can I suggest you buy a copy of UKHO SN Chart 1607 (POD). Imray will print the charts (other dealers are available).

DB. The table is predicting the height of tide at the time shown.

 

[Daydream believer]

DB. The table is predicting the height of tide at the time shown.

So what is 00-50 all about

 

[tillergirl]

00 = 12 midnight; 50 = 50 minutes; hence 00:50 = 1250am (GMT). so at 1250am the PLA predict for Friday 11th July to have a height of tide of 3.54m
01 = 1am etc, etc.