Using boats on moorings to assess tidal streams

[Lucky Duck]

Yesterday evening I made my first night time approach to a well known Solent River, noting the moored boats were pointing downstream I made my approach to the mid river pontoon allowing for the flood tide.

When I got up this morning I noticed most of them were on fore and after moorings

 

[Seajet]

There are often back eddies at the side of rivers & channels too; I always try to spot the way the bubbles or scunge / foam are going beside fixed points like pontoons or moorings, there's usually one or the other - but I have no idea what causes either !

 

[[70521]]

At the turn of the tide the boats around me point in all sorts of directions for at lease an hour.

 

[Dockhead]

Yesterday evening I made my first night time approach to a well known Solent River, noting the moored boats were pointing downstream I made my approach to the mid river pontoon allowing for the flood tide.

When I got up this morning I noticed most of them were on fore and after moorings

Funny!

Like Seajet -- I look at particles floating in the water next to the particular pontoon I am trying not to smash into. You can never be entirely sure just from the state of the tide, because of all the eddies and weird currents in the river. The Hamble will surprise you every time, and the ebb, especially, can be a real byatch at springs!

 

[johnalison]

Getting things spectacularly wrong is one of the joys of cruising, second only to watching others do the same. It's some years since we tried to set off with the "orange mooring cable" still attached.

 

[jac]

Funny!

Like Seajet -- I look at particles floating in the water next to the particular pontoon I am trying not to smash into. You can never be entirely sure just from the state of the tide, because of all the eddies and weird currents in the river. The Hamble will surprise you every time, and the ebb, especially, can be a real byatch at springs!

Aint that the truth. Coming into the Hamble last Sunday afternoon I was expecting the tide to be ebbing as about 90 minutes before LW but no tidal flow seen around the marks at the entrance, A bit further up, SOG and the Log seemed to show a slight flood of about 1 knot yet by the time we got to the Fuel berth at Port Hamble we had just under a knot against us ( ebbing.) Still an hour and 1/2 before low tide so just goes to show that what may be happening at one place is not the same as what is happening where you land.

 

[Roberto]

the way the bubbles or scunge / foam are going beside fixed points like pontoons or moorings, there's usually one or the other - but I have no idea what causes either !

they are a typical indication of a density current front, ie two masses of water with different densities moving in different directions, as it can be the case in purely tidal estuaries, where salinity evolution has a well defined pattern over the tidal cycle (other estuaries types may show predominance of salt or fresh water components)

if you are on fresh (less dense) water and moving towards the denser water, the usual pattern is 1.colour change, then 2.debris, at the surface, eventually 3.foam, past the foam you are in denser water, a part of which is going "under" the fresh water one, the current will have changed direction

 

[Seajet]

I think the most pertinent phrases so far are ' particles in water ' and ' X I'm trying not to bash into ' !

Like the dozen monkeys with typewrighters trying Shakespeare, I bet a dozen software bods couldn't hope to programme a simulator with all the variables mooring / berthing...

 

[Seajet]

they are a typical indication of a density current front, ie two masses of water with different densities moving in different directions, as it can be the case in purely tidal estuaries, where salinity evolution has a well defined pattern over the tidal cycle (other estuaries types may show predominance of salt or fresh water components)

if you are on fresh (less dense) water and moving towards the denser water, the usual pattern is 1.colour change, then 2.debris, at the surface, eventually 3.foam, past the foam you are in denser water, a part of which is going "under" the fresh water one, the current will have changed direction

Roberto,

thanks ! I'm not sure that explains all of the foam but it's a very good start.

 

[Roberto]

Roberto,

thanks ! I'm not sure that explains all of the foam but it's a very good start.

Maybe someone hiding inboard one of the boats while taking a shower

 

[Lucky Duck]

Yesterday (late) evening’s muck up was confusing Hurst lighthouse with Lepe cardinal buoy then when realising the two were not the same being unsure about what it was for probably too long.

Likely lesson about tiredness when sailing in the dark after a full day at work

 

[johnalison]

Yesterday (late) evening’s muck up was confusing Hurst lighthouse with Lepe cardinal buoy then when realising the two were not the same being unsure about what it was for probably too long.

Likely lesson about tiredness when sailing in the dark after a full day at work

I can believe that. I once spent a very anxious hour at 4am wondering why the E Margate buoy wasn’t doing what I thought it would do until it turned into the red sector of the N Foreland lighthouse.

 

[Poignard]

In the absence of any other indicators, an easy way to detect which way the current is flowing in a tidal river is to turn your boat across the river momentarily, and looking at some fixed object or light, see in which direction she is moved sideways.

 

[john_morris_uk]

A ten year old thread resurfaced..!

 

[Poignard]

A ten year old thread resurfaced..!

Two muck-ups in ten years is pretty good going! Wish I could say the same

 

[DJE]

In the absence of any other indicators, an easy way to detect which way the current is flowing in a tidal river is to turn your boat across the river momentarily, and looking at some fixed object or light, see in which direction she is moved sideways.

I find that pick-up buoys on any unoccupied moorings are a reliable indicator. They always lay down-tide of their main buoy.

 

[Poignard]

I find that pick-up buoys on any unoccupied moorings are a reliable indicator. They always lay down-tide of their main buoy.

Quite right, although I was responding to the OP's mention of a situation at night, where you might only be able to make out lights or large objects.

 

[AntarcticPilot]

In many places, both wind and tide affect the way boats lie to their moorings. I pass along the Walton Channel where there are many moorings, and commonly see boats that are lying at an angle to the tidal current, which is constrained by the channel. Obviously, the stronger the wind the greater the effect, but it is quite usual for boats to be lying at an angle to the current, and hence somewhat across the channel.

 

[johnalison]

In many places, both wind and tide affect the way boats lie to their moorings. I pass along the Walton Channel where there are many moorings, and commonly see boats that are lying at an angle to the tidal current, which is constrained by the channel. Obviously, the stronger the wind the greater the effect, but it is quite usual for boats to be lying at an angle to the current, and hence somewhat across the channel.

With wind against tide, the boat’s position is unstable, in that there are usually two possible positions for it to take up, and it is not unknown for a moored boat to flip round quite suddenly, usually just as one arrives to pass by. As a general rule, I don’t reckon you’ll go far wrong when picking up a mooring to approach it at the same angle as other boats are lying.

 

[justanothersailboat]

At certain states of wind and tide, when I get back to my mooring buoy all the sailing yachts are at one angle and the motorboats at quite another, then there are a few fore and aft moored things in the mix, so there is no possible straight run at the buoy... just weaving back and forth like crazy. It's been good training, but I think I would struggle in a less nippy boat.