While many of our community based natural habitats projects are on hold, we have been able to restart some ecological survey work such as the plant monitoring Maria has been doing on the nature reserve. Thanks to funding from City of York Council we have also been conducting surveys on Osbaldwick Beck to gather as much baseline information as possible before proposed engineering projects take place at St Nicks and Hull Road Park over the next year. We have been busy recording signs of water and otter, mapping river features and vegetation and surveying river health.
The survey method we use for river health involves taking a sample of what freshwater invertebrates live in the water by a process called kick sampling – disturbing the water and riverbed with your foot and then sweeping behind with a net for 3 minutes, followed by 1 minute searching plants and under stones. Afterwards we rinse out as much silt and fine sediment as possible before we start identifying what’s there as otherwise, in urban areas like St Nicks especially, you can end up with very murky water to try and spot things in! We then decant the net into trays of clear beck water and sit on the riverbank to see what we’ve found.
A range of different invertebrate groups are included in the survey and they get different scores depending on their pollution tolerance. For example, leeches, worms and hoglouse are much happier in, or tolerant of, polluted water and score lower in the survey than things like caddisflies, beetles or shrimps. River pollutants can include chemicals such as fertilizers, detergents and oils, as well as high build-up of silt which reduces oxygen levels and can smother the grow of plants which invertebrates need to thrive.
This survey method gives us both a one-off river health score, which allows us to compare different survey areas, and importantly a baseline score to compare against through regular surveys on that same area. By repeat surveying we can detect any pollution incidents, or monitor the effects of any changes to the beck such as the proposed engineering works.
We have been conducting these surveys at intervals along the urban reaches of Osbaldwick Beck and the early results are what you might except, if you know the area. In Hull Road Park the beck is heavily modified being much wider than its natural state and has several weirs. These modified features mean the beck flow loses its energy and deposits lots of silt. This also has a negative knock-on effect on the health of the beck at St Nicks downstream. Just upstream of the park the scores are a significantly improved. Here the beck has significantly less
silt as it still has many of its natural features including its width, more meanders (natural bends) which create a much better flow.
These survey results really highlight the potential for significant improvement to the health of
the downstream section of Osbaldwick Beck if the proposed engineering projects go ahead as planned, and are successful. Here’s hoping.
Written by Natural Habitats Manager Jonathan