River Ecology & Freshwater Habitat Surveys
There are several standard methods used to survey riparian habitats depending on the information required. Planning applications within sites designated for species such as lamprey or shad may require a specialist ichthyological survey or river habitat survey and appraisal. Please get in touch with us at the onset of your project so we can advise on the appropriate survey required.
River Habitat Surveys and River Corridor Surveys
River Habitat Surveys are an assessment of the ecological state of a river or stream corridor. They are used to characterise and assess the physical structure of rivers and streams. Spot-checks are used to record features at evenly spaced intervals along a 500m reach. These features include: channel substrata and flow type, habitat features, modifications to the channel and banks, vegetation types, vegetation structure of the banks and bank-top, and land-use. May and June are considered the most suitable months to carry out River Habitat Surveys.
River Corridor Surveys map defined reaches of river of approximately 500m length. Areas are divided into the aquatic zone, marginal zone, bankside zone and the adjacent riparian zone. The plant or tree communities and species are recorded, as well as substrata and physical features, and habitat use, where applicable.
Both survey types are habitat-based approaches rather than comprehensive species accounts. They can be used to identify the impacts of works in or near rivers, to assess the conservation value of a river or to suggest opportunities for habitat enhancement or management.
Freshwater macro-invertebrates are reliable indicators of water quality as they differ in their tolerance to pollution levels. Different species of macro-invertebrates are associated with varying levels of nutrients and flows. Species composition and quantity vary depending on the type of waterbody and water quality. Surveys are best carried out in the summer months, ideally June to August. If the purpose of the survey is to identify the macro-invertebrates present in a freshwater river or stream, there are a few methods available. The most popular is kick and sweep sampling; where a pond net is placed on the riverbed and the area upstream is disturbed for a designated number of minutes. This is repeated at different habitat types until all areas have been sampled. An additional one-minute hand search of large stones is also carried out. The macro-invertebrates from each netting are placed into a sorting tray with water and identified before being released at the same point as the collection. Specimens of difficult taxa are taken for laboratory determination.
These methods can be applied to assess the impacts of works in or near rivers and associated land. If an ecologically adverse impact is predicted, mitigation measures may include a precautionary working method statement to avoid or reduce ecological impacts such as pollution and increased sedimentation, and a management plan for the maintenance and restoration of the riparian habitat.
Please contact us to discuss your requirements for river habitat surveys and other river ecology support.