River conditions

Safety when the river breaks its bank

When the river breaks its bank after very heavy rainfall, it can block access to the club from Robertsons Drive (see pictures below). Remember that only a few inches of flowing water can be dangerous so take no risks wading in the water.

 

Navigation during a high tide

The risks of a high tide are:

  • river flow direction reversed
  • debris
  • a strong stream

Landing when the flow direction is reversed

When the tide comes up the river may flow in the opposite direction to normal. Since it is safer to land upstream, in this situation club rules state that crews should land in the opposite direction to normal. Navigating corners may pose a challenge when the flow direction is reversed due to steerspersons being used to navigating in a normal flow direction. 


Debris

During a high tide debris may come upstream from Netham Weir, for example branches, logs, wood with nails sticking out, etc. These can easily rip a fin out or put a hole in the bows. If you encounter this sort of debris you should immediately curtail your outing in order to avoid damage. Best plan to be downstream of the club when the stream turns so as not to get stranded upstream by debris coming up past the club.

Navigation in a strong stream

A strong stream could be caused by heavy rainfall or a tide. When travelling with the strong stream you will move a lot faster than normal. Just as when driving, your stopping distance will be increased and your cornering ability reduced. When travelling against the strong stream, the boat can get pushed across the river very quickly, especially when taking a corner. Assess whether the steersperson is competent for the conditions.

 

Updates from Twitter

 

 

Real-time river level information

Environment Agency River Levels - this shows the river level from an automated measurement station below Netham Weir. This is usually updated several times a day. When you see spikes these are high tides. This data is available on a Twitter feed @riverlevel_0439.

Based on observations on 11/01/2014, when the river is flowing steadily, approx 0.6m at Netham Weir = top of the black tiles at Ariel.

Based on observations on 29/02/2016, when the river is flowing steadily, approx 0.3m at Netham Weir = bottom of the slipway at Ariel.

There is another station at Keynsham (above the Hanham weir). Link. (0.6m at Keynsham ≈ 0.3m at Ariel at 20/03/16)

 

 

 Predicting river levels

Rainfall

  • Any heavy rain in the Bristol Avon Catchment may cause the river level to rise approximately 12 hours later and it may not return to normal for 2-3 days. After heavy rain the catchment will be saturated so any further heavy rain will certainly cause the river to rise again. After extended periods of rain / flooding, the river will take several weeks to return to normal.
  • Environment Agency Flood Warnings - for the Lower Avon Area. They keep track of the amount of rainfall in the last 24 hours and the forecast for the next 24 hours, and indicate quite accurately what may be coming down the river in the near future.

Tides

  • If there is a high tide above about 12.5 metres this will normally cause the river to rise at the club. However, bear in mind that the location of a high or low pressure centre in the Atlantic can affect the sea level in the Bristol Channel, which means under some weather conditions the actual level can deviate from the predictions.
  • If the river is already swollen due to rainfall this can suppress the effect of smaller tides coming up to us (12.5 - 13.5m).
  • 14 metres is a very high tide. Anticipate the stream changing and debris well ahead of the high tide time.
  • Tide Tables - add one hour to these Avonmouth times to convert to tides at the club - add another hour in the summer to convert from GMT to BST. This link shows 1 month of tides but the tables for the next 12 months are available from the Harbour Master. 
  • Different tide table providers use different datums but all the tide heights given on this page use the data from the NTSLF tables linked to above.

 

The Avon

We know all about our Avon (which comes from Old Brythonic abona, "river"). It runs from its source in Acton Turville (quite close to Bristol) then heads away from Bristol through Malmesbury, Chippenham, Trowbridge, then back again through Bath, but don't forget there are many River Avons in Great Britain. Don't get confused when you go rowing at Evesham, it's not the same Avon!

 

3 Jan 2014

3 Jan 2014

 Jan 2014

River map

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