Fish assemblage response to rehabilitation of a sand‐slugged lowland river

The impact of excessive sediment supply on river channels has been described in many areas of the world. Sediment deposition disturbance alters habitat structure by decreasing channel depth, changing substrate composition and burying woody debris. River rehabilitation is occurring worldwide, but information is scant on fish assemblage responses to rehabilitation in sediment‐disturbed lowland rivers. Sediment removal and large woody debris (LWD) replacement were used to experimentally rehabilitate habitat along a 1500 m stretch of the Glenelg River in western Victoria, Australia. Using an asymmetrical before‐after control‐impact (BACI) design, fish were captured before and after the reach was rehabilitated, from two control reaches and from a ‘higher quality’ reference reach. After two years post‐rehabilitation monitoring, the fish assemblage at the rehabilitated reach did not differ from control reaches. Temporal changes in taxa richness and the abundance of Philypnodon grandiceps, Nannoperca spp. and three angling taxa occurred after rehabilitation (winter 2003) compared with the before period (winter 2002), but these effects did not differ between rehabilitated and control locations. Highest taxa richness and abundances occurred at the reference location. High salinity coincided with the timing of rehabilitation works, associated with low river discharges due to drought. The negative effects of other large‐scale disturbances may have impaired the effectiveness of reach‐scale rehabilitation or the effects of rehabilitation may take longer than two years to develop in a lowland river subjected to multiple environmental disturbances. Copyright © 2009 John Wiley & Sons, Ltd.     

Flume study of the hydraulic effects of large woody debris in lowland rivers

As a part of a study investigating the hydraulic effects of large woody debris (LWD) in lowland rivers, a series of small-scale experiments were conducted in a rectangular glass-walled recirculating flume. These experiments were undertaken to determine the order of magnitude of the increase in flood levels caused by LWD at different positions within a channel cross-section. Position variables that were considered in these experiments were height above bed, angle to flow direction, and separation distance in the direction of flow. This study was undertaken to quantify the hydraulic benefits (primarily reduced flood levels) gained by the removal of LWD from lowland rivers, which is a common practice in several countries. From an integrated river management perspective it is necessary to weigh any hydraulic benefits of LWD removal up against the environmental costs of loss of faunal habitat, and possible geomorphic instability. The results of these experiments indicate that the levels of LWD commonly occurring in the lowland rivers of southeastern Australia seldom cause any significant effect on flood levels. However, where LWD occur at channel constrictions, or where unusually high densities of LWD are present, the effect on flood levels will be significant.     

POTENTIAL LARGE WOODY DEBRIS RECRUITMENT DUE TO LANDSLIDES,BANK EROSION AND FLOODS IN MOUNTAIN BASINS: A QUANTITATIVE ESTIMATION APPROACH

In‐depth knowledge of the fluvial corridor and surrounding slopes and forest vegetation is needed for a better understanding of wood recruitment or inputs to rivers. The information available in Central Spain on hydrogeomorphic processes and forest distribution enabled the evaluation of potential wood recruitment from three sources: landslides, bank erosion and fluvial transport during floods on a regional scale. The method presented here is based on a geographical information system (GIS) and on multi‐criteria and multi‐objective assessment using fuzzy logic principles. First, the areas potentially affected by landslides, bank erosion and floods were delineated, and a vegetation analysis was carried out to obtain the vegetation resistance and forest density. Several scenarios were proposed based on the process frequency and severity. Using this method, the volume of potentially available wood can be estimated for each scenario. Fourteen river basins in populated areas were selected for further analyses and field survey. Observations of in‐stream storage of woody debris and tree disturbances were used to interpret the woody debris dynamics throughout the watershed and validate the obtained results. This method offers a suitable approach to define a watershed's capacity to recruit wood material to streams by delineating the source areas and estimating the order of magnitude of the wood volume in each case. The results may be useful to characterize the dynamics of woody debris from the perspective of the potential hazard of its transport during floods, and they can also be used for forest and river management and restoration. Copyright © 2012 John Wiley & Sons, Ltd.     

Post‐flooding distribution and characteristics of large woody debris piles along the semi‐arid Sabie River,South Africa

The formation of large woody debris (LWD) piles has a profound impact on channel patterns and riparian succession in temperate rivers. The opportunity to study LWD along the Sabie River, a river in the semi‐arid region of Kruger National Park, South Africa, arose in February 2000 after a significant flood (c. 100‐year return interval) removed a large proportion of the fully mature riparian forest and other plant communities. Much of the uprooted vegetation was deposited as LWD piles (woody vegetation accumulations deposited on the ground > 0.1 m³) throughout the riparian and upland zones. In this article we describe the spatial distribution patterns of LWD as related to geomorphic channel type and flood frequency zone, and assess pile composition characteristics six months after the flood. Within the areas surveyed there were 68 LWD piles per hectare, the median size of LWD piles was 4.6 m³ but pile sizes (by volume) varied widely. Pool/rapid geomorphic channel types had the highest density of LWD piles (79 ha^?1) and the largest piles (by volume) were in the bedrock anastomosing channels (mean = 124 m³). Piles were larger in the seasonal and ephemeral flood frequency zones (mean = 54 m³ and 55 m³) than piles in the active zone (c. 2 m³). The patterns of distribution and volume of LWD will affect the subsequent development of vegetation communities as debris piles form a mosaic of patches of surviving organisms and propagules that can strongly influence the initial trajectory of succession. The amount, distribution, and subsequent decomposition of LWD are different from that reported for temperate rivers, suggesting that the role of LWD may be different on non‐floodplain rivers such as the Sabie in semi‐arid South Africa. Copyright © 2004 John Wiley & Sons, Ltd.     

MORE EXOTIC AND FEWER NATIVE PLANT SPECIES: RIVERINE VEGETATION PATTERNS ASSOCIATED WITH ALTERED SEASONAL FLOW PATTERNS

Natural flow regimes are important for sustaining riverine vegetation. The regulation of river flows to provide water for agriculture often results in changes to flow timing. This study assesses the impact of altered seasonal flow patterns on riverine flora. Within temperate Australia, we surveyed the vegetation of five lowland rivers, three of which have large dams that alter their seasonal flow patterns; the other two are unregulated. From four to six sites were selected on each river, and these were classified into three levels of regulation based on the extent to which the timing of their seasonal flow patterns were altered. Sites were surveyed in winter and the following summer. Permanent quadrats were also established at a number of the surveyed sites and resurveyed every 3 months. Of the 267 plant taxa identified, 145 were exotic (non‐native). More exotic taxa and fewer native taxa were associated with increasing level of seasonal flow inversion (regulation). In particular, greater numbers of short‐lived exotic terrestrial taxa and fewer native woody taxa were associated with increasing level of regulation. Some exotic woody species (e.g. willows) were more common in the unregulated rivers and may have life‐history traits favoured by the natural seasonal flow patterns of study area. Multivariate analyses showed that level of regulation had a significant effect on the overall composition of the riverine vegetation. Our results provide support for the hypotheses that flow regulation adversely affects native species diversity and increases the vulnerability of riparian zones to invasion by exotic species; however, these effects are dependent on plant species' life‐history strategies. Our study highlights the importance of natural seasonal flow patterns for sustaining native riverine plant communities. Flow management aimed at maintaining or restoring ecological values should consider seasonal flow patterns. Winter/spring flow peaks may be particularly important for the recruitment of native riverine plants, especially trees and shrubs, and reducing the extent of exotic annuals and grasses. Copyright © 2012 John Wiley & Sons, Ltd.     

GEOMORPHOLOGICAL CONTROLS ON VEGETATION RESPONSES TO FLOW ALTERATIONS IN A MEDITERRANEAN STREAM (CENTRAL‐WESTERN SPAIN)

The expected recovery of the natural conditions of large regulated rivers over the distance downstream from a dam is limited by relative tributary size according to the Serial Discontinuity Concept; however, geomorphology may also influence the recovery process. We examined the woody vegetation of the riparian zone in seven river segments distributed along the regulated reach of the Tiétar River in central‐western Spain, which flows through two distinct geomorphic templates. Whereas the annual runoff has decreased by 30% on average along the entire studied reach following the construction of the Rosarito Dam and the initiation of field irrigation in the region, the magnitude and frequency of the peak flows decreased by 30% immediately downstream from the dam but recovered the natural values with the distance downstream. We evaluated the recovery patterns toward the natural riparian conditions by comparing woody species composition, diversity and distribution of vegetation patches established prior to and after dam completion. Our results did not indicate a recovery gradient of any of the analysed vegetation attributes downstream from the dam. Instead, we found that the difference in the slope of the stream channel and banks, the width of the valley and the size of substratum particles among the surveyed patches were factors that significantly mediated dam and tributary effects on vegetation and influenced the degree of vegetation recovery. Hence, the maintenance of the intensity of the flow alteration scheme by the numerous water withdrawals and the low tributary contributions, coupled with differential geomorphological characteristics along the reach, overwhelmed the natural tendency for the river to restore its natural conditions with distance downstream. Improving water management and, particularly, restoring endangered riparian ecosystems require a detailed understanding of existing and potential woody species behaviour across the geomorphological settings of rivers. Copyright © 2012 John Wiley & Sons, Ltd.     

Recent changes in riparian vegetation: possible consequences on dead wood processing along rivers

Little is known about changes in the composition of dead wood jams along rivers and the possible consequences of any such changes on the river ecosystem. Although tree zonation along the upstream‐to‐downstream continuum is weak and highly variable from a system to another, a clear transition appears in the piedmont zone, which is reflected by transitions in dead wood sources as well as for dead wood transport, storage and decomposition processes. In this paper, we focus on large lowland rivers of southwestern France, where riparian vegetation is increasingly fragmented, reduced in area and/or is entirely replaced by planted forests (poplar plantations). The amount and the potential role of dead wood is practically unknown in these rivers. One reason is that French legislation obliges landowners and public service managers to remove all material from the stream in order to maintain unobstructed river flows. The other reason is that unlike pristine streams in northern regions, these rivers have been regulated for several decades (Adour River) or even for several centuries (Garonne River). The vegetation component of the managed riparian landscape has changed in particular as a result of i) a decrease in stream dynamics, ii) the replacement of natural forests by planted ones, and iii) the invasion of natural communities by introduced woody species. The possible consequences of biological invasions on the role of dead wood jams are discussed in light of: i) a local study of wood jams along a moderately modified system; ii) changes observed in the composition of trees along the Adour River over the past 10 years; iii) a regional case study involving two chosen species. Whereas white willow populations are declining along streams in southwestern France, the box‐elder, introduced from the United States, has spread extensively in the last two decades. Statistical models would suggest that competitive pressures are limited between these two species, boxelder is expected to replace white willow in the near future as a consequence of an increase in river regulation and global warming. This can be expected to have important consequences on dead wood dynamics, and on the management of woody debris, especially since trends indicate a replacement of softwood species by hardwood species. Copyright © 2003 John Wiley & Sons, Ltd.     

Regulation leads to increases in riparian vegetation,but not direct allochthonous inputs,along the Colorado River in Grand Canyon,Arizona

Dams and associated river regulation have led to the expansion of riparian vegetation, especially nonnative species, along downstream ecosystems. Nonnative saltcedar is one of the dominant riparian plants along virtually every major river system in the arid western United States, but allochthonous inputs have never been quantified along a segment of a large river that is dominated by saltcedar. We developed a novel method for estimating direct allochthonous inputs along the 387 km‐long reach of the Colorado River downstream of Glen Canyon Dam that utilized a GIS vegetation map developed from aerial photographs, empirical and literature‐derived litter production data for the dominant vegetation types, and virtual shorelines of annual peak discharge (566 m³ s^?1 stage elevation). Using this method, we estimate that direct allochthonous inputs from riparian vegetation for the entire reach studied total 186 metric tons year^?1, which represents mean inputs of 470 gAFDM m^?1 year^?1 of shoreline or 5.17 gAFDM m^?2 year^?1 of river surface. These values are comparable to allochthonous inputs for other large rivers and systems that also have sparse riparian vegetation. Nonnative saltcedar represents a significant component of annual allochthonous inputs (36% of total direct inputs) in the Colorado River. We also estimated direct allochthonous inputs for 46.8 km of the Colorado River prior to closure of Glen Canyon Dam using a vegetation map that was developed from historical photographs. Regulation has led to significant increases in riparian vegetation (270–319% increase in cover, depending on stage elevation), but annual allochthonous inputs appear unaffected by regulation because of the lower flood peaks on the post‐dam river. Published in 2010 by John Wiley & Sons, Ltd.     

基于河道治理的河流生态修复

阐述河流整治带来的负面影响 ,论证对受损的河流进行生态修复的必要性 .基于河道治理的河流生态修复是指河道形态和河床断面的修复及恢复丧失的河岸带植被和湿地群落 ,可采用的具体方法有 :恢复河道的连续性 ;重现水体流动多样性 ;给河流更多的空间 ;慎重选择河道整治方案 .在介绍国内外相关研究进展情况的基础上对河流生态修复的研究和应用提出合理建议 .     

EVALUATION OF RIPARIAN HABITAT RESTORATION IN A LOWLAND RIVER

For many years, navigable lowland rivers have been embanked artificially or suffered from substantial shipping wave action, leading to habitat degradation. Recently, riparian habitats were restored by creating foreshores and spawning grounds in the river Yser, a lowland river in Flanders, Belgium. The aim of this paper was to evaluate the role of these restored habitats for spawning and nursery of juvenile fish. To cover a wide range of anthropogenic disruption, four riparian mesohabitat types were selected and compared, ranging from semi‐natural over artificial spawning grounds and foreshores to artificial embankments. Juvenile fish were subjected to sampling by using electrofishing between June and September 2009 at different microhabitats located in five sites of each riparian mesohabitat type. Juvenile fish strongly preferred natural riparian habitats, whereas artificial embankments showed the lowest species richness, abundance and functional organization of juvenile fish species. Restored riparian habitats appeared to be an appropriate alternative for artificial embankments in navigable lowland rivers but still score significantly less than natural habitats. Juvenile fish avoided bare microhabitats but did not prefer any other microhabitat type (reed, woody or grassy vegetation), emphasizing the importance of microhabitat diversity. This paper provides valuable insights into riparian habitat restoration to river managers and stakeholders. Copyright © 2011 John Wiley & Sons, Ltd.     

Impact of a 100‐year flood on vegetation,benthic invertebrates,riparian fauna and large woody debris standing stock in an alpine floodplain

This paper investigates the impact of a 100‐year flood in May 1999 on community composition and large woody debris standing stock in an alpine floodplain (Isar, Germany). Detailed pre‐flood data sampled from 1993 to 1998 are compared with the situation directly after the flood. In those parts of the Isar floodplain mainly covered with pioneer vegetation prior to flooding, the coverage of unvegetated gravel bars increased by 22% following the flood. However, the flood did not remove larger amounts of older successional vegetation stages (willow thickets, floodplain forest). No significant changes in the benthic invertebrate fauna were recorded. The lowest densities of riparian ground beetles (Carabidae) within the study were recorded one month after the flood. Two months later, the ground beetle densities increased to the highest values ever recorded, indicating the ground beetle's high potential for recolonization. These results highlight the degree of resilience of both the aquatic and the riparian invertebrate fauna. The flood also caused a significant increase in large woody debris standing stock; in one section the number of logs increased tenfold and the volume increased by a factor of 20, leading to the assumption that most woody debris in alluvial flood‐plains is provided by catastrophic events. Copyright © 2004 John Wiley & Sons, Ltd.     

Management of vegetation encroachment by natural and induced channel avulsions: A physical model

Flow regulation and water abstractions may change the complex relationship between river hydraulics, morphology, and riparian vegetation. As a result, rivers are likely to decrease their dynamics, increase the amount of vegetation, and modify their habitat structure. Flood events provide a natural mechanism for removal of invasive vegetation and recreation of natural floodplain habitats. This work aims at evaluating and quantifying how gravel‐bed braided rivers naturally control vegetation encroachment through morphological processes and the impact of both naturally occurring and induced avulsions. Flume experiments were conducted in a 24‐m‐long x 1.6‐m‐wide channel filled with well‐sorted sand and constant longitudinal gradient at 0.01 m/m. Once a braided network developed, the flume was seeded with Eruca sativa at a density of 1.5 seeds/cm² and grown until an approximate height of 1.1 cm. Experiments evaluated low‐, medium‐, and large‐flood events and documented morphological changes and impacts to vegetation at four intervals during the experiments. High‐resolution images captured approximately 3 m above the flume were used to produce accurate Structure‐from‐Motion‐derived topography and orthoimagery (average errors 2 mm). Vegetation dynamics were observed to be highly variable and depend on local morphological changes and bank erosion. Discharge is the first‐order control on vegetation removal, but our results show that occurrence of avulsions significantly increases vegetation removal. The experiments highlight that a relatively small amount of sediment relocation can be an effective tool to induce avulsions and reduce vegetation encroachment on regulated rivers.     

Floristic differences between riparian corridors of regulated and free-flowing boreal rivers

Riparian ecosystems are central elements in many landscapes because of their shape, diversity and function as filters and corridors. They are also among the environments most disturbed and threatened by humans. Human-induced changes in riparian vegetation and flora were assessed by comparing free-flowing and regulated rivers in northern Sweden. Although riparian vegetation structure is rather uniform along free-flowing rivers, it varies distinctly along regulated rivers because of different water-level fluctuations in storage reservoirs, run of the river impoundments and unimpounded but regulated reaches. The total species richness of vascular plants per river in the riparian zone was similar between four free-flowing and four regulated rivers in northern Sweden. However, species richness per 200 m long site was considerably lower, and almost all groups of species were more species-poor per site in the regulated rivers due to perturbations caused by regulation. Both free-flowing and regulated rivers showed an increase in the species richness of ruderal plants towards the coast. In contrast, the species richness of natural plants showed different longitudinal patterns in the two types of rivers, and differences were largest along the middle reaches of the rivers. The reasons why responses in vegetation and flora to human perturbation varied downstream along regulated rivers are not known, but factors such as different disturbance patterns, irregular distribution of remnants of former riparian soils and vegetation and differences in regional plant species richness and plant dispersal along the river corridor may be important.     

Environmental factors related to anuran assemblage composition,richness and distribution at four large rivers under varied impact levels in southeastern Brazil

The margins of large rivers are usually impacted by human settlements and activities, which may affect the occupancy and use of riparian habitats by many organisms. Among vertebrates, amphibians are likely the most sensitive to environmental changes, and they can be used as a model to identify attributes of the riparian habitats that are important for the maintenance of high species richness and functional diversity. We studied anuran assemblages in four large rivers of the Velhas River basin in southeastern Brazil during one year, focusing on features of the rivers and riparian habitats that influence species distribution. We tested whether a river under greater anthropogenic impact would shelter less species compared to three rivers of equivalent size under lower impact level, and whether lower species richness related to lower availability of preferred microhabitats. We found soil type at river margin and riparian vegetation structure to be the main factors influencing anuran distribution. Species richness was positively related to microhabitat diversity and availability of preferred microhabitats, which were the lowest in the most impacted river. Most species recorded at the rivers were not breeding there, and were present in larger numbers during the dry season, when temporary bodies of water dry at the vicinities of the large rivers. Conservation of a broad extension of the riparian habitat (200 m or more) would be efficient both to provide appropriate microhabitats for anurans and to maintain connectivity between breeding sites and large, permanent rivers used by several species during the dry season. Copyright © 2010 John Wiley & Sons, Ltd.     

Large wood debris recruitment on differing riparian landforms along a Gulf Coastal Plain (USA) stream: a comparison of large floods and average flows

In southeastern Coastal Plain streams, wood debris can be very abundant and is recruited from extensive forested floodplains. Despite importance of wood debris, there have been few opportunities to examine recruitment and redistribution of wood in an undisturbed setting, particularly in the southeastern Coastal Plain. Following extensive flooding in 1994, measurements of individual downed trees (species, dbh, orientation, distance from base‐flow channel and condition) were made across replicated riparian landforms in a Gulf Coastal Plain 5th‐order stream. Annually, the fate of these trees was determined and newly recruited trees were noted. More than 300 downed trees have been recorded. Recruitment varied across landforms with more constrained reaches having greatest mortality. Total tree mortality varied substantially across years. Generally, tree recruitment was greatest in years with substantial floods (1994 and 1998). For each riparian landform type, tree mortality was correlated with the maximum daily flow during the period preceding annual debris surveys. This relationship was particularly strong for sand ridges (r² = 0.942) and low terraces (r² = 0.915), but was significant for floodplains (r² = 0.413). Greatest rates of debris recruitment per maximum daily flow were observed for sand ridges followed by low terraces. Flood characteristics also influenced debris recruitment. The 1994 flood was caused by a tropical storm and resulted in a rapid rise in streamflow. Much of the debris recruited during this flood was from toppled trees and was oriented parallel to the stream channel. In contrast, the 1998 flood was preceded by a wetter than average winter with more gradually rising flows and there was no relationship between riparian landform and debris characteristics. These results indicate that wood recruitment dynamics in Coastal Plain streams are complex. Wood recruitment rates are controlled by cyclical variations in climate interacting with riparian geomorphology. Infrequent high flows appear critical in the maintenance of the instream debris pool. Copyright © 2007 John Wiley & Sons, Ltd.     

SEDIMENT DYNAMICS IN THE RESTORED REACH OF THE KISSIMMEE RIVER BASIN,FLORIDA: A VAST SUBTROPICAL RIPARIAN WETLAND

Historically, the Kissimmee River Basin consisted of a broad nearly annually inundated riparian wetland similar in character to tropical Southern Hemisphere large rivers. The river was channelized in the 1960s and 1970s, draining the wetland. The river is currently being restored with over 10 000 hectares of wetlands being reconnected to 70 river km of naturalized channel. We monitored riparian wetland sediment dynamics between 2007 and 2010 at 87 sites in the restored reach and 14 sites in an unrestored reference reach. Discharge and sediment transport were measured at the downstream end of the restored reach. There were three flooding events during the study, two as annual flood events and a third as a greater than a 5‐year flood event. Restoration has returned periodic flood flow to the riparian wetland and provides a mean sedimentation rate of 11.3 mm per year over the study period in the restored reach compared with 1.7 mm per year in an unrestored channelized reach. Sedimentation from the two annual floods was within the normal range for alluvial Coastal Plain rivers. Sediment deposits consisted of over 20% organics, similar to eastern blackwater rivers. The Kissimmee River is unique in North America for its hybrid alluvial/blackwater nature. Fluvial suspended‐sediment measurements for the three flood events indicate that a majority of the sediment (70%) was sand, which is important for natural levee construction. Of the total suspended sediment load for the three flood events, 3%–16% was organic and important in floodplain deposition. Sediment yield is similar to low‐gradient rivers draining to the Chesapeake Bay and alluvial rivers of the southeastern USA. Continued monitoring should determine whether observed sediment transport and floodplain deposition rates are normal for this river and determine the relationship between historic vegetation community restoration, hydroperiod restoration, and sedimentation. Published in 2011 by John Wiley & Sons, Ltd.     

Novel plant communities limit the effects of a managed flood to restore riparian forests along a large regulated river

Dam releases used to create downstream flows that mimic historic floods in timing, peak magnitude and recession rate are touted as key tools for restoring riparian vegetation on large regulated rivers. We analysed a flood on the 5th‐order Green River below Flaming Gorge Dam, Colorado, in a broad alluvial valley where Fremont cottonwood riparian forests have senesced and little recruitment has occurred since dam completion in 1962. The stable post dam flow regime triggered the development of novel riparian communities with dense herbaceous plant cover. We monitored cottonwood recruitment on landforms inundated by a managed flood equal in magnitude and timing to the average pre‐dam flood. To understand the potential for using managed floods as a riparian restoration tool, we implemented a controlled and replicated experiment to test the effects of artificially modified ground layer vegetation on cottonwood seedling establishment. Treatments to remove herbaceous vegetation and create bare ground included herbicide application (H), ploughing (P), and herbicide plus ploughing (H + P). Treatment improved seedling establishment. Initial seedling densities on treated areas were as much as 1200% higher than on neighbouring control (C) areas, but varied over three orders of magnitude among the five locations where manipulations were replicated. Only two replicates showed the expected seedling density rank of (H + P) > P > H> C. Few seedlings established in control plots and none survived 1 year. Seedling density was strongly affected by seed rain density. Herbivory affected growth and survivorship of recruits, and few survived nine growing seasons. Our results suggest that the novel plant communities are ecologically and geomorphically resistant to change. Managed flooding alone, using flows equal to the pre‐dam mean annual peak flood, is an ineffective riparian restoration tool where such ecosystem states are present and floods cannot create new habitat for seedling establishment. This problem significantly limits long‐term river and riparian management options. Copyright © 2010 John Wiley & Sons, Ltd.     

论河流生态修复

本文以河流系统诸功能与河流健康之间的关系为主线，从人与河流关系的发展与变化出发，探讨了原始自然阶段、工程控制阶段、污染治理阶段和河流生态系统修复和改善等四个阶段的河流特点和治理条件，分析了各个阶段河流系统平衡的特征和影响因素，初步建立了河流健康诊断指标体系，提出了河流生态修复的主要原则。河流生态修复的总体目标是恢复河流系统健康，实现人与河流的和谐共存。河流生态修复主要技术包括：缓冲区修复、植被恢复、河道补水、生物-生态修复、生境修复、水生生物群落修复技术等。本文采用层次分析法的基本思想，探讨了河流健康、河流功能、功能要素和生态修复措施四个层次的关系，同时指出了实现河流生态修复的步骤。