A Field Guide to British Rivers. George Heritage

      Foreword

      Temperate rivers are influenced by many factors including geology, climate, soils, sediment type, flow and human activity. The complex interactions of the non‐anthropogenic controlling factors have led to a wonderful variety of river form in the British Isles. Sadly, however, almost all temperate rivers in the United Kingdom have suffered significant and long‐lasting modification and management that has all but destroyed this variety, instead creating simplified conduits for water and sediment designed primarily to drain the land and reduce flood risk. This book is intended to illustrate this variety, highlighting the many forms that temperate river systems take in the United Kingdom. In this volume, we cover upland and lowland channel types and include the full range of substrate conditions from bedrock through boulder, cobble and gravel through to silt‐dominated systems. In doing this, we describe examples gathered from over 30 years each of research and practical experience working with rivers and set these in the context of the current scientific knowledge to illustrate the natural functioning of temperate river types. We hope this will act as a practical, context‐sensitive and more sustainable template for the restoration and re‐naturalisation of degraded channels in the United Kingdom and as a working set of guidelines for those interested in understanding more about the rich variety of temperate river types. In doing this, we know other examples exist (e.g. the practical guides from the UK River Restoration Centre), and so we intend this volume with its balance between science and practicalities of river management to compliment these other approaches but essentially to act as a stand‐alone guide.

      It is interesting to reflect on the reasons behind the present degraded state of temperate rivers and the common acceptance that this current state is “how a river should be.” Significant, almost wholesale, channel and floodplain modification occurred throughout the agricultural and industrial revolution as valley bottomlands were exploited for food production and industrialists sought to utilise the power of rivers for energy for manufacturing activities. River channels were moved, straightened, embanked, and deepened, and the new channels had their banks protected with wood and stone. While large extents of natural wooded vegetation was removed as part of this activity, trees (but, more often than not, monoculture) were planted along bank margins to prevent them moving from their designated route. Floodplains and later uplands were drained to improve land for crops and grazing and urban rivers were completely channelised to prevent flooding. Generations have now grown up with these modified rivers, and as a result, we have now accepted that they are somehow “natural.” Our own limited experience of rivers has led to the widespread belief that rivers are liquid ribbons in the landscape; static systems, immovable in the landscape and not part of the surrounding floodplain fields and meadows. We talk of rivers “bursting their banks” – a negative term implying that overspilling to occupy the floodplain temporarily is somehow unnatural. Increasingly, as management of temperate rivers reduces on the part of national agencies, requests are made to “fix” rivers by “repairing” banks, dredging sediment, and removing wood and other vegetation to recreate the “neat” channels people remember from days gone by. Such perceptions are not aided by the current teaching of river science in schools. Geography and environmental lessons in schools perpetuate outdated concepts; for example, textbooks concentrate on meandering systems and pool‐riffle sequences and decades old river typologies that, despite rivers being continua, divide catchments into upper, mid‐reach and lowland meandering sections – ignoring the irony that the latter are rarely permitted to be mobile nowadays.

All these modifications have not just altered the physical form of temperate rivers and valley bottoms, they have also fundamentally impacted on the flow regime and the way in which river systems erode, transport and store sediment. As such, we are left with systems that are a neutered shadow of their former selves, where both natural processes and natural form are severely impacted resulting in a highly degraded river channel and valley bottom. The simple single‐thread channel, often featureless and constrained, dominates our riverine landscapes with many other river types now all but extinct. Many rivers also now experience more extreme flows across the year, with winter flood extremes testing flood defences to their limits and spring and summer low flows that border on drought conditions. Whilst both extremes may have their origins in climate change, there is no doubt that they have been exacerbated by inappropriate upland drainage management impacting on the flow paths and speed of water once it has hit the ground.

      Such a situation should not be allowed to continue and fortunately several factors are presently operating that provide encouragement that more natural river and floodplain systems can make a resurgence. The first is the current reluctance amongst statutory bodies to continue with the intensive management of watercourses due to their routine maintenance budgets being significantly reduced from those of a decade or two ago. This is giving many rivers a chance to begin to erode and deposit sediment once again; however, channel response in often highly localised and more extreme than would occur naturally as failing protection creates “hotspots of change.” Alongside this, there is an increasing recognition that impacted flood regimes require addressing at source rather than just at flooding hotspots, and Natural Flood Management approaches to slow flood flows and store flood water are gaining traction in terms of catchment‐oriented efforts to restore river and floodplain connectivity and channel dynamism. More recently, it has been recognised

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