Tuesday 2nd November 2021. Water, water everywhere!

A light frost, the first of the autumn, greeted me when I arrived at the Reserve this morning but, as the day wore on, I found myself peeling off layers of clothing in brilliant sunshine with almost no breeze. Perfect conditions for the nets, if a little bright. The birds weren’t cooperating though. There was little sign of overhead passage, just a few hundred Woodpigeon and a couple of Redwing and Mistle Thrush and not much on the ground either. In the end, just 23 birds were trapped in five hours and half of these were re-traps. The final totals were: 1 Blackbird, 2 Blue Tit, 3 Cetti’s Warbler, 4 Chiffchaff, 2 Dunnock, 3 Goldcrest, 3 Great Tit, 3 Robin and 2 Wren.

However, with no pressure from the nets, I was able to complete a number of minor maintenance tasks, which had been accumulating. The first job was to replace the snapped mist net pole in Blaca ride. I had measured its diameter on my last visit and made up a sleeve at home to cover the break. Tightening a couple of self-tappers fixed it in about five minutes. A good start.

The bridge to Marsh Ride – now suitably restrained!

After the wet latter half of October with 60% more rain than average, South Milton Stream was pretty full and the water table had clearly risen in the reedbed. The stream was lapping around the base of my bridge to Marsh ride. It has been swept off its mountings a couple of times before so I hammered in two scaffolding poles to stop it drifting downstream in the future. Marsh ride is the lowest point in that part of the reedbed. Years of walking up and down the net ride have created a channel, probably only 10-20cm lower than the surrounding marsh but enough to show up as prone to flooding on Environment Agency maps.

Surface water in Marsh Ride
Changes to the depth of South Milton Stream following the cessation of dredging

Whilst on the subject of flooding. The northern boundary path, in the region of the boardwalk, is regularly inundated when the coastal sandbar is high and the reserve manager was concerned that the cessation of dredging in South Milton Stream would exacerbate the problem. Today gave me the perfect opportunity to take some photos and measure the current depth of the channel. About an additional 20cm of sediment has accumulated since my last measurement but the boardwalk area remained accessible, confirming mine and Nick’s assessment that it is water impounded behind the sandbar rather than the stream that causes the flooding. The chart above shows the amount of sediment accumulated since the last dredging operation in 2014.

No flooding at the Boardwalk bridge despite the accumulation of sediment in the stream!

The water levels in South Milton Stream, between the sewage works and the boardwalk, lapped between 10 and 30cm below the banks and it now has a much more natural appearance when compared to the 2m deep, steep-sided channel left after previous ditching operations. There is no doubt that this will raise the water table leading to a healthier reedbed and, as an added bonus, at no cost to Devon Birds or the ecology of this part of the reserve. It’s still early days but, at the present rate of sedimentation, my hope is that the stream will eventually look like this in the height of summer, albeit with much lower flows. The images below, travelling downstream from the public footpath towards the boardwalk, show the gradual raising of the water table and the transition from almost no reeds to a much denser stand of almost pure reed.

South Milton Stream above the STW, where the gradient is now too steep for sedimentation to occur. Note the depth of the channel and the absence of reeds.
South Milton Stream 100m downstream at the STW outflow. A shallower channel and reeds beginning to appear.
South Milton Stream a further 200m downstream, just below Marsh ride. Contrast this with the first image above.

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