A Field Guide to British Rivers. George Heritage

Читать онлайн книгу.

A Field Guide to British Rivers - George Heritage


Скачать книгу
to improve watercourse form and function through restoration is having little or no measurable impact on floodplains.

Pie charts depict the cause of hydromorphic degradation in the UK.

      Source: www.riverhabitatsurvey.org/wp-content/uploads/2012/07/RHS.pdf

      It is interesting to review the figures above against the Water Framework Directive measure of river health currently being used across Europe. Entwistle et al. (2019a) used floodplain land‐use data for 2017 broken down according to current water body status generating 2975 auditable units. Water bodies presently at Good status were selected (n = 375), arable and horticulture covers in excess of 50% of the floodplain area on around 15% of Good status water bodies, this increases to around 50% for area under improved grassland and when the two are considered together between 70 and 75% of Good Status water bodies are covered by at least 50% farmland. Around half of these water bodies are utilised over 90% by farming.

      The preceding section summarises several studies relating to river and floodplain degradation; however, it remains difficult for the reader to understand exactly what has happened to watercourses and valley bottoms in England. Rivers seen in the landscape today are often regarded as “natural” systems with little regard to the actual levels of degradation they have suffered. This is perfectly understandable as we have grown up with heavily modified and managed systems, and we have few natural analogues left against which we can judge the degree of alteration. “Stability” is seen as desirable with neatness and uniformity favoured above natural functionality. Fortunately, this attitude is changing as the economics of river and floodplain management has resulted in reduced river training and a consequent increase in the influence of natural fluvial processes. Many systems are showing small but significant signs of recovery towards a better functioning system aligned with current catchment controls. Recovery has not always been back to a previous river state before human intervention as conditions in the catchment have changed significantly enough to cause a state change in our rivers, but their diversity is improving.

Photo depicts typical heavily modified lowland system with artificial flood protection embankments, channel straightening and dredging, and removal of in-channel and riparian vegetation. The Yorkshire Derwent at Yedingham. Photo depicts typical heavily modified upland system, straightened, walled, and dredged. The Upper Whit Beck at Low Lorton.

Photo depicts semi-natural multi-channel network on the River Narr.
Скачать книгу