Floods at Christmas 2020 and Early 2021

The Environment Agency measures water levels regularly along the River Great Ouse including at St Ives lock. The water levels on Holt Island are close to the levels measured at this station but will be a little higher due to the mediaeval bridge and the new bridges slowing the water down which in turn raises the level.

On Christmas Eve the waters came up very fast and were at their highest for a good number of years. They reached 1.52 metres above datum level at the lock, the highest in this century. It was several days before it went down round about New Year.

On 14th January the water level rose sharply and went up to 1.24 metres where it stayed. During the next four weeks the water remained high, going up to 1.33 metres, only dropping down on 10th February. Two days later it was back down to normal levels. On the Island at the information board, the water measured 1.35 metres at its highest for the Christmas flood and 1.14 metres in January/February.

This is one of the longest periods that Holt Island has been under water. It will have had an effect on the flora and fauna of the Island – but probably only a short term effect on the fauna. The ground feeding birds such as Blackbird, Song Thrush and Dunnock moved off the Island and fed in nearby areas which were not flooded. Most of the insectivorous birds including the Blue Tits, Long tailed Tits and Tree creepers will have remained and carried on as usual.

The series of wet winters we have had recently will favour plants such as the yellow flags and water mint and will discourage things like the creeping thistle. It may also help the sedges, rushes and reeds. The flood waters deposit a lot of silt which is very nutritious to certain plants such as the comfrey and nettles, being potassium rich.

There is a lot of fallen timber on the Island particularly the sallow, this will rot faster as the damp conditions favour the fungi that feed on them which in turn helps the beetles and invertebrates which live on the wood giving food for the Woodpeckers and Tree creepers.

The fish have been affected with almost 2000 which were left behind when the flood receded being returned to the river. There were a good range of sizes particularly of Roach, Rudd and Perch with small numbers of Bream and Dace. An Eel was also returned to the river suggesting the river is in good condition with little pollution.

There is also the physical damage. The water got into the Holt at Christmas as all the boardwalk was under water, some areas for significant periods. Work is required to repair the damage including replacing rotten boards, and where the non-slip surface has come off, replacement is needed with non-slip strips each requiring 20 screws. The silt which is so beneficial to plants also coats the boardwalk and needs to be cleaned off. For a month and a half work had to stop on the Island which has delayed projects and prevented work such as extending the fedge (living willow fence) along the Back Water bank of the Island as by the time it could be done the osiers had their buds opening.

A lot of last years reed has been broken and rafts of this have drifted and collected in areas on the Island, this will all break down and rot but it will need moving in places.

Although the flood appears to have caused problems they are short lived and will sort themselves out; nature will quickly bounce back.

Julian Limantani

Beehive washed away   Debris washed up

 Beehive floated off platform, wood off storge area

   Debris washed up on boadwalk floated off
Water up to floor of Holt   Broadwalk under water
 Water up to floor of Holt    Boardwalk under water


Dipping pond floated and turned through 45 degrees

 Photographs © Julian Limantani