The current state of the use of large wood in river restoration and management

Trees fall naturally into rivers generating flow heterogeneity, inducing geomorphological features, and creating habitats for biota. Wood is increasingly used in restoration projects and the potential of wood acting as leaky barriers to deliver natural flood management by ‘slowing the flow’ is recognised. However, wood in rivers can pose a risk to infrastructure and locally increase flood hazards. The aim of this paper is to provide an up‐to‐date summary of the benefits and risks associated with using wood to promote geomorphological processes to restore and manage rivers. This summary was developed through a workshop that brought together academics, river managers, restoration practitioners and consultants in the UK to share science and best practice on wood in rivers. A consensus was developed on four key issues: (i) hydrogeomorphological effects, (ii) current use in restoration and management, (iii) uncertainties and risks and (iv) tools and guidance required to inform process‐based restoration and management.     

基于河流动态自然过程的生境修复策略

全球气候变化和土地利用方式的改变对河流的动态自然过程带来不利影响。而目前人们对河流的修复重治理效果而轻自然过程,特别是风景园林与相关学科的交叉与融合研究较少,缺乏聚焦中、微尺度基于河流动态自然过程的生境恢复方法指导。基于此,从雨洪淹没、潮汐消落的河流动态自然过程规律着眼,提出对应的生境修复策略：1)恢复水陆边界的自然属性,重建泛洪区和河岸的联系;2)梯度式快速恢复近自然河岸带生境植被;3)连通感潮河涌湿地和营建关键生物生境,实现多种共生生物栖息地的再生。该方法有助于恢复河流长期、稳定的自由流动,生境在河流动态潮汐作用下异质性不断提高,从而提高河流湿地的生物多样性,还能为城市中心的居民提供亲近自然的休闲空间,以期在河流生境修复实践方面为风景园林和多学科融合提供新思路。     

Time, scale and change in river landscapes: the jerky conveyor belt

The basis for a scientific understanding of river landscapes is fluvial geomorphology. However, the base of the subject in university research schools has meant that a simple interpretation of river landforms has been missing from UK landscape studies. This paper attempts to redress the balance by setting down the basic time and space scales along which our rivers have sculpted their valley floors, floodplains and channels. The fluvial landscape is interpreted in terms which are relevant to management; centuries of flood protection works have rendered most of our river channels inactive. Future management, with landscapes in mind, will need to incorporate (or restore) dynamic fluvial processes. A programme of education is required to match the public appreciation of 'wild' rivers with the information and understanding needed to manage them sustainably.     

A decision support system for identifying the habitat quality and rehabilitation potential of urban rivers

Few habitat survey, classification or assessment methodologies have been developed specifically for urban or heavily engineered rivers, and yet these rivers need careful assessment if management options are to be considered and prioritised in an economically and environmentally effective way. This paper presents a refinement of a previously proposed urban river survey (URS), which is a modification of the Environment Agency's River Habitat Survey. It then describes indices and classifications that have been developed from URS data and that provide a link between the type of engineering applied to a stretch of urban river and its habitat characteristics. Finally, some simple decision trees and scenario‐modelling tools are presented that allow (i) newly surveyed urban stretches to be classified and (ii) some simple scenarios of channel management change to be assessed in order to prioritise management options for stretches of urban river across urban catchments.     

The effects of flood defences on riparian vegetation species richness and abundance

It is widely recognised that flood disturbance has important consequences for the biodiversity of riparian zones and that inundation allows nutrients and organic matter to be exchanged and recycled between aquatic and terrestrial ecosystems. Previous research has focused on the impacts of dams on riparian biodiversity, with little consideration given to the impacts of flood defences. The current study investigated the extent to which the presence and age of flood defences controls riparian plant richness and abundance. Sites without flood defences were found to have significantly higher species richness and abundance. In contrast, flood defence age was found to have little impact although turnover was high between sites with old and new defences. Flood management should therefore focus on more sustainable options that work with natural processes where possible, such as washlands.     

基于城市河流半自然化的生态防洪对策——河滨缓冲带与柔性堤岸设计导引

旨在将城市河流半自然化与生态防洪对策落实到城市设计层面。根据观测水位、防洪、防潮标准确定缓冲带鼓励淹没范围、堤顶控制点标高,结合亲水性活动、适宜土地利用方式及景观要素,给出8种典型缓冲带断面设计及相应护岸生态工法。设计导引以海河下游为例,采用绩效控制、示例设计方法,主要内容包括目标-策略表、控制要点与编制方法表、示例设计图、应用索引图等。导引有助于消除防洪设施带来的视线遮挡、增强河滨缓冲带土地利用复合性与公共性,缓解防洪与亲水性、城市区生态用地与河滨土地稀缺性等矛盾,以保持河滨持久性活力。     

Children's perceptions of river landscapes and play: what children's photographs reveal

The insights that children's photography can provide into children's perceptions of river landscapes and play opportunities are focused upon, based on an analysis of over 500 photographs and comments generated during visits to two London rivers by children aged nine to eleven from three nearby schools. In their photographs, the children recognized the aesthetic appeal of specific natural features of the river landscapes, particularly trees. Some also appreciated broader river landscape 'views'. The rivers themselves were seen as littered and polluted. Dangers were identified, but these were not seen as unmanageable. The children recognized the special character of the rivers as play places affording varied, adventurous and manipulable play opportunities, but wanted cleaner, safer, more accessible and managed rivers. Some differences were found in the responses of boys and girls and in the children's responses to the two rivers. The urban children taking part in the study showed little understanding of the functions that living and decaying riverside vegetation might have in river ecology, indicating a need for more environmental education.     

城市防洪排洪规划重要因素探讨

对城市防洪排洪规划而言,"内河"与"外江"应赋予其不同的意义,文章对其进行新的界定。城市防洪排洪规划要确定防洪标准,本文通过分析论述,提出针对一个城市各条河流、溪流其设计防洪标准应分别确定,主要从汇水面积、其保护对象重要程度和人口多少等方面考虑确定。本文还针对福建城市地形特点,分析强调了采用高地自排对降低城市排洪压力,提高城市安全度的重要意义。     

Incorporating catchment to reach scale processes into hydromorphological assessment in the UK

Hydromorphological pressures and the measures undertaken to address them are an important element of the delivery of the WFD within the United Kingdom. While assessment procedures currently employed gather useful morphological information for river reaches and their immediate margins and some process information, crucial information on key processes is missing and information gathered on the riparian zone and floodplain is limited. This article presents a newly developed framework that enables existing data to be placed within a multiscale, process‐based context. The framework has great promise for diagnosing hydromorphological pressures, identifying where and how natural recovery is likely to take place, and where more interventionist restoration techniques may be needed. The ability to consider trajectories of river channel adjustments could help us understand how watercourses are still responding to historic changes, improve our confidence in applying restoration measures and the likely hydromorphological consequences of future climate changes.     

A conceptual model of riparian forest restoration for natural flood management

There is an increasing emphasis on using natural processes, including riparian forest restoration, to enhance the ecological, hydrological and geomorphological functioning of watercourses. However, we have insufficient knowledge on how the supply and retention of in‐channel wood from riparian forest stands changes with age, with inferences typically based on data from terrestrial forests. This presents a challenge in estimating the efficacy and functional lifespan of restoration projects. In this paper, we use a riparian forest growth model to show there is a lag of up to 40–50 years between the start of forest growth and trees delivering wood to the channel that is large enough to resist fluvial transport, anchor logjams and so increase channel complexity and hydraulic resistance. Resource managers need to account for realistic timescales over which changes promoted by riparian woodland restoration will occur and may need to consider using interim engineered logjams as the forest develops.     

Restoring Dynamic Fluvial Processes in Urban Rivers: Learning from the Aire and Isar Rivers

In process-based restoration, the objective is not to create a complex river form directly; instead, interventions are intended to “prompt” the natural processes to restore such forms. The improvements in ecological conditions are actually made over time by flowing water during floods (using the stream’s energy), and by the growth of riparian vegetation (using incoming solar energy). On the Aire River in Geneva, ecological function was restored to a formerly canalized river by providing the river with an espace de liberté. A grid of channels cut into the valley bottom allowed the river to freely flood, erode its bed and banks, and deposit bars, creating complex surfaces on which riparian vegetation established to support the food web of the riverine ecosystem. The diamond-shaped bits of land left between these channels (“lozenges”) gradually erode and evolve as the river migrates, creating complex channel forms. The Isar River in Munich restoration involved adding coarse sediment load, creating erodible bed and banks in place of formerly rigid boundaries, expanding process space for river migration, erosion, and deposition, and increased human access to the river over 8 km. Since restoration, natural transport of sediment has resulted in deposition of gravel bars, whose forms evolve during floods, supporting diverse habitats. The Isar and Aire Rivers provide compelling examples of processbased restoration meeting 4 criteria for process-based restoration: space, energy, materials, and time. They demonstrate the possibilities of urban river restoration to achieve both ecological and social goals through restoration of fluvial process.     

Assessing the impact of changes in landuse and management practices on the diffuse pollution and retention of nitrate in a riparian floodplain

In many European lowland rivers and riparian floodplains diffuse nutrient pollution is causing a major risk for the surface waters and groundwater to not achieve a good status as demanded by the European Water Framework Directive. In order to delimit the impact of diffuse nutrient pollution substantial and often controversial changes in landuse and management are under discussion. In this study we investigate the impact of two complex scenarios considering changes in landuse and land management practices on the nitrate loads of a typical lowland stream and the riparian groundwater in the North German Plains. Therefore the impacts of both scenarios on the nitrate dynamics, the attenuation efficiency and the nitrate exchange between groundwater and surface water were investigated for a 998.1 km(2) riparian floodplain of the Lower and Central Havel River and compared with the current conditions. Both scenarios target a substantial improvement of the ecological conditions and the water quality in the research area but promote different typical riparian landscape functions and consider a different grade of economical and legal feasibility of the proposed measures. Scenario 1 focuses on the optimisation of conservation measures for all natural resources of the riparian floodplain, scenario 2 considers measures in order to restore a good status of the water bodies mainly. The IWAN model was setup for the simulation of water balance and nitrate dynamics of the floodplain for a perennial simulation period of the current landuse and management conditions and of the scenario assumptions. The proposed landuse and management changes result in reduced rates of nitrate leaching from the root zone into the riparian groundwater (85% for scenario 1, 43% for scenario 2). The net contributions of nitrate from the floodplain can be reduced substantially for both scenarios. In case of scenario 2 a decrease by 70% can be obtained. For scenario 1 the nitrate exfiltration rates to the river drop even below the infiltration rates from the river, the riparian floodplain in that scenario represents a net sink for river derived nitrate. As the nitrate contributions from the investigated riparian floodplain represent only a small proportion of the total nitrate loads within the river (1% p.a.) the overall impact of the scenario measures on the nitrate loads at the river outlet remains small. However, during the ecologically most sensitive summer periods under current conditions nitrate contributions from the riparian groundwater of the Lower and Central Havel River (which covers only 5% of the area of the Havel catchment) represent more than 20% of the river loads. By the implementation of the investigated landuse changes within the research area the groundwater derived nitrate contributions could be halved to only 10% during summer baseflow conditions.     

生态型城市水安全格局构建初探

近些年来．国内许多城市接连遭受洪涝灾害的侵袭,城市水安全（防洪安全与防涝安全）受到严重威胁。本文基于这样一种背景．提出应该从过去过度依赖工程措施转变为以充分利用水系生态系统自身的泄洪、蓄水、排渍等功能为前提来保障城市水安全。以湖南省安仁县为例．利用GIS对水系生态系统进行防洪安全格局和防涝安全格局分析．识别出对城市防洪防涝有重要意义的战略关键点和区域一即相应规模和格局的河流、湖泊、湿地等水系景观要素．通过对这些要素制定相应的规划导则,构建生态型城市水安全格局。     

The Impact of Intensive Dairy Farming Activities on River Quality: The Eastern Cleddau Catchment Study

Pollution from farm wastes has been one of the principal causes of deterioration in river quality in recent years. However, little is understood of how, and which, farming activities affect the chemical and biological quality of rivers. To address this problem, a field study has been initiated in the Eastern Cleddau catchment, West Wales, to investigate relationships between land use, farm waste management practices and river quality.
Water quality of small tributaries in this area is poor, and intensive chemical monitoring has shown that discharges from farmyards are a major source of pollution. Rainfall has been shown to exacerbate this effect either through field runoff or wastes washing directly from the farmyards. The status of benthic macroinvertebrate communities in these tributaries is poor and, typically, only a few pollution-tolerant species are present.
Small tributaries from farms appear to affect both the water chemistry and biology of larger watercourses, although this effect may be quite localized.
Future research will look at ways to reduce the impact of farm wastes on river quality. This will provide the basis for producing recommendations and guidelines for catchment management aimed at minimizing pollution of rivers from farming practices.     

Assessment of the hydromorphological state of Carpathian rivers above and below reservoirs

The article presents the results of an assessment of the hydromorphological state of selected Carpathian rivers in sections above and below the reservoirs. An attempt has also been made to assess the impact of reservoirs on the hydromorphological conditions and quality of river habitats. The research was based on the River Habitat Survey (RHS) method. The synthetic indices Habitat Quality Assessment (HQA) and Habitat Modification Score (HMS) were calculated on the basis of the gathered data for each section studied; this allowed the hydromorphological qualities of the rivers to be assessed numerically. The reservoirs interrupt river continuum, and they alter different biotic and abiotic elements of natural environment. However, this study has shown that the operation of reservoirs does not always negatively impact the hydromorphological conditions of rivers that reflect their habitat quality. The influence of reservoirs on a river's hydromorphological state above and below a reservoir's location may be neutral, but it also can improve the habitat conditions of a river.     

Rescuing Big Rivers Damaged in Industrial Civilization

Large rivers with beautiful landscapes were dreamlands to the author. However, every time upon his arrival to riversides, he was shocked for the heavily polluted rivers that are dirty, messy, and smelling. Engineered dikes and dams made of concrete and steels for a greater height and hardness are built by cities along rivers. As more highways and railways built along rivers, vehicles run at a faster speed, scaring any life who wants to or has to access the water. Most of the tributaries are no longer free flow but end up as hard ditches and the water is polluted heavily. Forests and wetlands are being damaged and eroded. All of these are resulted from humans’ material desires and lack of respect for nature. Nevertheless, ecological civilization may encourage people to appreciate the beauty of nature and get a thorough understanding on river ecosystems and their services, accompanied by systematic planning and implementation of territorial ecological restoration. Moreover, laws and regulations on large river management should be put in place, and efforts should be made to break the worship of grey engineering approaches to flood control. It is expected that nature-based ecological approaches for a better resilience and sustainability in flood management can be more effective to ensure water safety.     

城市河道综合整治规划设计探索

针对城市河道综合整治问题,结合工程实例,阐述了城市滨水区规划的原则、景区性质及发展目标,探讨了城市空间布局、景点设计、植物配植规划、防洪规划、交通规划等规划构思,论述了河道整治和滨水地带规划建设可持续发展的途径.     

Rivers and river restoration: a child's-eye view

Research suggest a high level of interest in the environment and in environmental action by children. Yet very little is known about how children perceive the natural environment. Despite the fact the children are one of the largest user groups of outdoor spaces, their views are rarely sought. The aim of this small qualitative study was to look at children's perceptions of river corridor environments, and specifically to look at their views on restoring our rivers. The children demonstrated a strong concern for the natural environment and supported the idea of river restoration. Natural features of river corridor landscapes were valued, but the children also valued highly other non-natural features which afford them opportunities for play and exploration. By talking to children, and also by analysing children's drawings and writings about rivers, the study aimed to gain a broader understanding of how children perceive the river environment, and how they might participate more fully in its management.     

Restoration of a chalk stream using wood: assessment of habitat improvements using the Modular River Survey

The installation of large wood and sediment berms to narrow the overwide channel of the River Bulbourne, Hertfordshire, aimed to restore geomorphological processes, improve channel habitat diversity and increase the amenity value of the park in which the river is located. The Modular River Survey provides a framework and suite of tools for river managers and volunteers to monitor and assess restoration activities. Applying this technique to the River Bulbourne before and after restoration demonstrated that the works increased physical habitat and vegetation complexity. The restored section was narrowed, substrate composition changed and the range of in‐stream vegetation morphotypes increased. The initial slight improvement in riparian habitat complexity immediately following the restoration is expected to increase further over time as the riparian vegetation develops and the restored section of channel matures. A public perception and recreational use survey reviewed how visitor experience and use of the park changed following restoration.     

Lowland Stream Restoration in Denmark: Background and Examples

Since 1982, Danish legislation on streams and drainage has included clauses which make it possible to implement river restoration. In this paper, the Danish shift in policy from drainage to the return of wetlands is described. To illustrate the new beginning on catchment management, two major river-restoration schemes, i.e. the River Brede demonstration project and the River Skjern Nature project, are presented. Both projects have been implemented and consist of many parts, including (a) returning the straight, regulated rivers back to their former meanders, (b) introducing better hydraulic interaction between the river and its meadows, and (c) establishing former lakes, bogs, ponds and marshes. Also, an increase in security against flooding has resulted, as the regulated 'water-motorways'have become more natural, with buffer-zones and retention of water in the restored features.