A dynamic model to predict responses of millets (Echinochloa sp.) to different hydrologic conditions for the Illinois floodplain–River

Millets grow on floodplain mud flats exposed when seasonal floods recede, and the seeds of this plant are an important food source for waterfowl during their spring and autumn migrations in the Mississippi Flyway. Productivity of millets along the Illinois River has declined because of unnaturally frequent floods that inundate the mud flats and drown the plants during the summer growing season. These small floods are caused by operation of the navigation dams on the main channel and by alterations of the floodplain and tributary watersheds and channels. Predictive models are needed to evaluate the most cost‐effective combination of approaches for restoring plant productivity. We developed a moist‐soil plant model that simulates millet growth on 1 m² in response to daily water levels during the summer growing season. The model responds to daily water depth, flood timing (within the growing season), and flood duration, and was qualitatively verified using historical (1938–1959) water levels and plant coverage for three areas along the Illinois River. In the absence of untimely floods, the model predicts net above‐ground primary productivity of ～500 g m^?2 yr^?1 and plant heights of up to 130 cm by the end of the growing season. As expected, growth declines with decreasing land elevation or with more frequent flooding (or a shorter duration of the dry period) at the same elevation. A dry period of >85 days is required to achieve at least 50% of maximum production during the growing season, which is somewhat longer than the 70‐day recommendation based on reported field observations. The model predictions of plant success or failure agree with historical observations, indicating that water regime is a major factor limiting plant success. Copyright © 2004 John Wiley & Sons, Ltd.     

Rehabilitating the floodplain of the lower River Dyje for fish

The lower reaches of the River Dyje were heavily modified between 1975 and 1985. The river was straightened, isolating its meanders and reducing its length by 22%. As a consequence, the river bed showed a markedly lower diversity in both hydrological and morphological characteristics. Because the River Dyje forms the state boundary between the Czech Republic and Austria, fluvial activity of the lower reaches is excluded. Along the River Dyje an active alluvium has been preserved, with approximately 1300 hectares in the Czech Republic and somewhat less in Austria. The flow regime in the lower reaches is regulated by 19 water reservoirs and a number of fishponds, with a total capacity of approximately 45% of the annual drainage. These modifications have distinctly impacted the living conditions of the indigenous ichthyofauna. Based on the results of our ichthyological investigations from 1994 to 2000, we have recommended a number of modifications that could improve the environmental conditions for fishes: (i) controlled flooding of the alluvial meadows, aimed at creating conditions for the spawning of phytophilous fish species; (ii) restoration of permanent connections between separated river meanders and the River Dyje to increase the hydrological and morphological diversity in the river bed; (iii) creation of artificial pools in the floodplain to provide more suitable habitats for fishes. Copyright © 2003 John Wiley & Sons, Ltd.     

Historical changes in hydrology,geomorphology, and floodplain vegetation of the Willamette River,Oregon

Historical trends in hydrology, geomorphology, and floodplain vegetation provide fundamental contexts for designing future management of large rivers, an area of fluvial research extensively informed by studies of historical channel dynamics. Changes in hydrology, channel structure, floodplain forests, and large wood were documented for the 273‐km main stem of the Willamette River from 1850 to present. Reduced sediment supply and frequency and magnitude of floods have decreased channel mobility and incised channels, leading to fewer gravel bars, islands, and side channels. Human alteration of channel morphology, vegetation, and bank hardening has exacerbated channel simplification caused by reductions in floods, sediment supply, and inputs of wood. A substantial number of floodplain channels reoccupied remnants of previous active channels inundated during recent floods, demonstrating functional but often forgotten role of historical geomorphic structure in modern floodplains and flood processes. In most reaches, area of floodplain forests in 1990 was only 10% to 25% of the area of forests in 1850. Abundance of wood in the wetted channel was generally greater in reaches with higher abundances of floodplain forests. Future trajectories will be influenced by legacies of the historical river but increasingly will reflect evolution of a new river shaped by human development, changing climate, and emerging hydrogeomorphic and vegetation processes. Understanding historical characteristics and anticipating future rates and patterns of ecosystem change provide fundamental contexts for restoring biophysical processes and structure in a large floodplain river.     

嫩江下游洪水演进及对洪泛区植被影响分析

为揭示嫩江下游洪水演进规律及对洪泛区植被的影响,利用MIKE FLOOD建立了嫩江江桥—大赉河段的一、二维水动力耦合模型,选取1998年与2013年汛期实测资料对河段糙率进行了率定与验证,并模拟了典型河段4种不同重现期洪水的演进过程。在此基础上基于2000—2019年MODIS卫星的MOD13Q1数据集,获取了不同洪水频率淹没范围内的植被指数(NDVI、EVI),评估了嫩江下游不同重现期洪水扰动对植被的影响。结果表明:模型在率定期与验证期的模拟效果符合甲级预报精度,模型模拟精度较高;不同重现期内的植被指数具有较强的季节变化规律,且洪水对植被具有明显的破坏作用,但这种破坏作用在嫩江流域周期性相对较短,表明该地区植被的可恢复性较强;同时受洪水频繁淹没程度影响,不同重现期的植被指数符合中度干扰假说。     

The effect of altered flow regime on the frequency and duration of bankfull discharge: Murrumbidgee River,Australia

On meandering rivers with well‐developed floodplains, bankfull stage has geomorphological and ecological significance because it approximates the level of connection between the channel and the floodplain. As a river rises to bankfull stage, sediment begins to be deposited on the floodplain, wetlands are progressively inundated and organisms migrate between the channel and floodplain habitats. On many rivers large headwater dams have reduced the frequency and duration of floodplain inundation downstream. However, the lack of reliable pre‐regulation flow data has made it difficult to quantify the effects of river regulation. This study used historical regulated and modelled natural flow data to determine the effects of regulation on the frequency and duration of bankfull flows on the Murrumbidgee River, one of Australia's largest and most heavily regulated rivers. In combination with floodplain surveys the flow data show that regulation has halved the frequency and duration of bankfull flows. This reduction in channel–floodplain connection has implications for the ecological health of the Murrumbidgee River. Copyright © 2005 John Wiley & Sons, Ltd.     

The influence of soil desiccation on plant production,nutrient uptake and plant nutrient availability in two French floodplain grasslands

The effects of summer soil desiccation on plant production and plant nutrient availability (determined by wet chemical extraction) in floodplain grasslands along the rivers Allier and Loire in France were investigated. Soil desiccation in these river floodplains is the result of human interference with the natural flooding regime of rivers, such as dam construction and gravel mining. Flooding periods along the Allier have a longer duration (maximum of 202 days as opposed to 38 days for the Loire). The main comparison was between floodplain grasslands along the two rivers. Additional comparisons were made between relatively high lying, wetter areas (‘ridges’) and low lying, drier areas (‘swales’) within both floodplains. Thus, areas with different soil moisture content were examined, independent of river influences. The availability of P was higher in the Allier floodplain than in the Loire floodplain, but it was similar between ridges and swales. It was concluded that P-availability was not related to soil wetness, but to river sedimentation. Plant production, plant nutrient uptake, and biologically mediated soil processes, such as N-mineralization and nitrification, were all higher on the wetter Allier floodplain and in the wetter swales. These higher process rates were noted where higher amounts of soil bound carbon and nutrients were found as well. Plant production, N-mineralization and nitrification were moisture limited at the dry ridge on the Loire floodplain, as moisture levels were below the wilting point here (pF>4.2). On the wetter parts of the floodplain, plant production was N-limited. This was concluded from low tissue N/P ratios (about 10) and a positive relation between plant production and N-mineralization. On the wetter parts, the rate of N-mineralization depended on the size of soil organic-N pools. The size of these pools was positively related to soil wetness, which can be interpreted as a positive effect of river flooding. Reduced flooding lowers the nutrient input to floodplains and contributes to the occurrence of soil desiccation in summer, which results in lower nutrient cycling and reduced accumulation of soil organic matter. These effects have negative consequences for important floodplain functions, such as nutrient retention and biomass production. © 1998 John Wiley & Sons, Ltd.     

A 12‐month sediment and nutrient budget in a floodplain reach of the River Adour,southwest France

The sediment and nutrient budget in the floodplain reach of the River Adour in southwest France has been examined over a 1‐year period (1991–1992). Outputs of total suspended matter, dissolved inorganic nitrogen (i.e. nitrate+ammonium ions) and dissolved inorganic phosphorus (DIP) and particulate phosphorus (PP) have been compared with inputs. Alternating phases of mobilization and retention are observed for all the elements considered. Low water periods in summer allowed retention of both soluble material (24–26% for inorganic nitrogen) and suspended matter (9–19%). However, mobilization of PP associated with suspended matter transport during these periods. Elevated discharges associated with increased rainfall during the autumn period induced significant mobilization for all elements. In contrast, the winter flood event gave rise to a retention of particulate material (i.e. suspended matter and PP, 11% and 26%, respectively), but a loss of soluble materials (5% for inorganic nitrogen and 186% for DIP). The spring flood event produced retention for particulate materials (26%) while inducing losses of inorganic nitrogen (9%) and gains of DIP (7.4%). These results are related to riparian vegetation and the dynamics of nutrient cycling within the floodplain. Copyright © 2000 John Wiley & Sons, Ltd.     

Historical patterns of river stage and fish communities as criteria for operations of dams on the Illinois river

The hydrologic regime of the Illinois River has been altered over the past 100 years. Locks and dams regulate water surface elevations and flow, enabling commercial navigation to continue year round. This study relates changes in water surface elevation to fish abundance in the river, and establishes target criteria for operating locks and dams. Using long‐term records of daily river stage, we identified ecologically meaningful hydrological parameters for eight gage locations along the Illinois River. Inter‐annual variability of a long‐term fisheries dataset beginning in 1957 was related to variability in stage, flood and recession duration, frequency, timing, and rate of change of water levels. Reversals in water surface elevation, maximum stage levels, and length of the spring flood were the most important parameters influencing abundance of age‐zero fishes in annual collections. Smallmouth buffalo (Ictiobus bubalus), black crappie (Pomoxis nigromaculatus), freshwater drum (Aplodinotus grunneins), and white bass (Morone chrysops) were most abundant in samples during years that approximated the natural water level regime. Of the 33 hydrologic parameters evaluated for the entire water year from an Illinois River gage site on La Grange Reach, all except average stage in January and Julian date (JD) of maximum stage had moderate or high hydrologic alteration based on the historical range of variation (RVA). The highest degree of hydrologic alteration was for minimum stage levels (1‐day, 3‐day, and 7‐day), rate‐of‐rise, and rate‐of‐fall. Other parameters that have been severely altered were 30‐day minimum stage, 90‐day maximum stage, and the annual number of water level reversals. Operations of the La Grange and Peoria locks and dams could be modified so water level variability would approximate that of the late 1800s, when fish and wildlife resources were abundant. The water regime could be regulated to maintain navigation and improve conditions for native plants and animals without increasing flood damages. Copyright © 2002 John Wiley & Sons, Ltd.     

Screening the Suitability of Levee Protected Areas for Strategic Floodplain Reconnection Along the LaGrange Segment of the Illinois River,USA

Levee‐protected floodplains along the 125‐km LaGrange Segment (LGS) of the Illinois River were screened for their abiotic suitability for alternative ecosystem services (ESs), including wetland creation, habitat, floodwater denitrification and flood‐tolerant agriculture. The suitability framework developed for this study builds upon the Land Capability Potential Index and is informed by the current understanding of the linkages between river hydrology, hydraulics, floodplain soils, floodplain vegetation and floodplain nutrient cycling. In addition to screening these floodplain areas for alternative ESs, we demonstrate how this framework can be combined with economic assessments of current floodplain services to inform how strategic floodplain reconnection (i.e. restoration of hydrologic linkages between river and floodplain for the purpose of flood mitigation and provisioning of alternative ESs) could be used to work towards sustainable floodplain management. Results show that ESs increase with upstream distance from the LaGrange Lock and Dam. This is attributed to the operation of the lock and dam generating a water level that would result in the inundation of a substantial portion of floodplain (>70 km²) up to ?60 km upstream if the levees were to be removed or set back. Comparison of the profits from current floodplain agriculture with the potential profits of flood‐tolerant agriculture suggests that overcoming the economic costs of floodplain reconnection within the LGS will likely require both conversion of reconnected floodplain lands to flood‐tolerant agriculture and payments for ESs. Copyright © 2016 John Wiley & Sons, Ltd.     

Influence of the flood regime on the reproduction of fish species with different reproductive strategies in the Cuiabá River,Upper Pantanal,Brazil

This study evaluated the influence of the flood regime of the Cuiabá River on the reproductive dynamics of fish species with different reproductive strategies. Sampling was carried out at ten sites in the basin, between March 2000 and April 2004. The reproductive strategies evaluated were long‐distance migrant (LM), short‐distance migrant (SM), sedentary with parental care (PC) and sedentary or SM with internal fertilization (IF). Period, duration and intensity of floods were the flooding attributes considered. Duration and time of spawning were evaluated using the index of reproductive activity (IRA), and inferences concerning reproductive allocation were based on the analysis of gonad weight. Reproductive success was evaluated based on the annual catch of young‐of‐the‐year of each species. Reproductive dynamics and flood regime were closely correlated; the reproductive peaks of fishes using all four strategies always preceded flood peaks. Intense floods favoured gonadal development of LM and PC, but were less important for IF. In relation to juvenile survival, the occurrence of floods appeared to be crucial for the strategies of LM, PC and IF, because such floods increased fish survival in the period of initial development. In contrast, SM appeared to be less dependent on floods for reproduction. These results indicate that, except for SM, floods have an important role in the recruitment of species using other reproductive strategies, and influence spawning success as well as juvenile survival. Copyright © 2008 John Wiley & Sons, Ltd.     

Temporal and Spatial Variation in Riparian Vegetation and Floodplain Aquifers on the Regulated Dolores River,Southwest Colorado,USA

The importance of flow variability and floodplain water table recharge for the establishment and long‐term survival of riparian vegetation has been well‐documented. However, temporal and spatial variation in floodplain aquifers has received less attention, although native species can have narrow tolerances for groundwater decline. Our observations of decreased cottonwood cover on floodplains and increased willow cover on river banks since dam completion on the Dolores River led to comparisons between three long‐term study sites above and below McPhee Dam. We summarize 5 years (2010–2014) of shallow groundwater well data from transects of three wells per site. Vegetation cover data were collected from quadrats and line‐intercept transects. In the willow zone, groundwater well levels mirror in‐channel flows and rarely drop below 0.6 m from ground surface. Willow cover and stem counts on point bars are higher at dammed sites. Wells in the cottonwood zone indicate that alluvial recharge happens only during prolonged peak discharge during spring snowmelt or dam release. Years with no dam spill reduced connectivity between surface flows and groundwater, and groundwater depth dropped to between 2 and >2.5 m. Long‐term data below the dam indicate that canopy cover of the dominant cottonwoods has declined over time (48% in 1995, 19% in 2003), especially in the wake of severe drought. Mature cottonwood cover is significantly higher at the undammed site (p = 0.025). Our results indicate that floodplain habitats below dams exist under artificially extreme drought and inform how biologically diverse riparian systems will be impacted by a drying climate. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of flood regime on tree growth in the floodplain and surrounding uplands of the Wisconsin River

Flood regime and vegetation flood tolerance interact to influence tree growth in riverine landscapes. We studied tree growth in floodplain and upland forests of the Wisconsin River. About a century ago, levees set back from the river were constructed on this floodplain. The levee restricts some floodplain area from overbank flood events, but leaves a portion of active floodplain still inundated by floods. We addressed two questions: (1) how do growth rates of flood‐tolerant and flood‐intolerant tree species in the floodplain differ with flood regime? (2) At the stand level, how does growth rate differ with flood regime and between floodplain and upland areas? Annual tree growth rates from 1991 to 2000 were determined from tree increment cores for both individual species and stands. Tree growth rates of individual species varied between flood regimes. The most flood‐tolerant species (Betula nigra and Fraxinus pennsylvanica) grew faster in areas with active flooding, while the growth of less flood‐tolerant species (Quercus velutina and Q. ellipsoidalis) was depressed in swales and active floodplain. However, stand‐level tree growth did not differ between the floodplain and upland, or between flood regimes within the floodplain. Therefore, variation in the growth of individual species may not scale up to create differences in stand‐level tree growth because forest community composition varies spatially with flood regime. We suggest that growth rates are similar among sites because each community comprises of species adapted to their current flood regime. Copyright © 2008 John Wiley & Sons, Ltd.     

塑造和维持黄河下游中水河槽措施研究

本文通过实测资料分析和泥沙数学模型计算的方法，就如何塑造并维持黄河下游中水河槽进行了系统的研究，分析了在未来可能的水沙条件下黄河下游中水河槽的规模，计算了小浪底水库不同出库水沙条件对塑造黄河下游中水河槽的作用，认为在目前的水沙条件下塑造和维持平滩流量约4000m3/s的中水河槽是可能和现实的，并进一步分析了影响中水河槽塑造和维持的主要因素，提出了塑造和维持黄河下游中水河槽的措施，试图为黄河下游防洪治理和维持黄河健康生命提供技术支持。图4表2参8     

长江中下游洪水位与河床冲淤关系初探

针对长江中下游近50年来部分水文断面如螺山、城陵矶洪水位抬升明显、高洪水位持续时间加长的问题,统计了大量水位、流量、水流含沙量以及河床地形等实测资料,并进行分析计算.结果表明,长江中下游洪水位变化与河段河床演变及河道形态变化密切相关,江湖淤积及河道形态变化是造成洪水位抬高及高洪水位持续时间加长的主要原因.     

黄河中游水沙频率关系研究

扼要指出进行黄河中游水沙频率关系研究的必要性,并通过对黄河中游部分连续泥沙观测序列的独立同分布性的检验,验证了建立黄河中游泥沙频率曲线的可行性以及泥沙序列对P-Ⅲ型分布曲线的适应性。在此基础上建立了黄河中游水沙序列的理论频率曲线,分析了黄河中游的水沙频率之间的关系,给出了一定泥沙频率条件下所对应的洪水发生的频率范围,对年径流量和输沙量的频率组合进行了量化,对水沙丰枯组合进行了确定,最后提出了有待于进一步研究的问题。     

Immediate downstream effects of the Petit-Saut dam on young neotropical fish in a large tributary of the Sinnamary River (French Guiana,South America)

The effects of artificially low runoffs in the Sinnamary River, French Guiana, South America, on flow patterns and on richness and abundance of young fish in Venus Creek, one of its main downstream tributaries were examined. After Petit-Saut dam's gates were closed, the areas adjacent to this tributary were never once flooded for the entire duration of the rainy season. The daily maximal averages of water speed at the tributary's mouth were found to be significantly increased. Young fish sampled using light-traps were less abundant and less diverse after dam closure. Young Characiformes appeared to be the most affected by these flow disturbances. These findings enabled us to develop a conceptual model of the consequences of impoundment on young fish assemblages through the modifications of tributaries and associated floodplains hydrology. Because of flow reduction in the river during the first year of impoundment, young fish that previously had a tendency of being trapped in tributaries and flooded areas were then at risk of being flushed away. The pattern of flow release by dam operations is known to be very different from natural flow variations. The consequences for downstream tributaries will be similar to those of channelization: lack of adjacent flooding areas and higher rates of downstream water transfer. How the recovery of downstream fish assemblages will occur is discussed. © 1998 John Wiley & Sons, Ltd.     

楚雄市龙川江橡胶坝设计与施工

橡胶坝是20世纪50年代以来出现的一种新型水工建筑物。它是一种结构简单、自重轻、抗震性能好、不阻水、泄洪蓄水操作方便的活动挡水坝。与同规模的常规拦河闸相比，约节省工程投资26％—50％。橡胶坝的坝袋先在工厂制造，到现场安装一般只需7—10d。云南省楚雄市在龙川江城区河段治理工程中采用了这种坝型。规划中共建4座橡胶坝，坝高3—3．5m。1、2号坝已于1999年4月建成，并经受了当年洪水和2000年洪水的考验。运行操作灵活、安全可靠，发挥了应有的经济和社会效益。     

黄河下游宽滩区滞洪沉沙功能与减灾效应二维评价模型及其应用

黄河下游宽滩区既是大洪水行洪滞洪沉沙的通道,又是滩区群众赖以生存和发展的家园,如何合理运用宽滩区是长期备受关注和争议的话题。本文在水沙统筹、空间统筹和时间统筹原则的指导下,建立了黄河下游宽滩区滞洪沉沙功能与减灾效应二维评价指标体系,构建了基于Pareto最优解的黄河下游宽滩区滞洪沉沙功能与减灾效应二维评价模型,利用1958、1982、1992和1996年4场洪水实测资料,对该模型的合理性进行了验证。应用上述模型对黄河下游宽滩区不同运用方式的12组二维数学模型计算方案进行了评价,结果表明,洪水量级对减灾效应影响显著;相同洪水条件下设防护堤并控制闸门运用(有闸)或分区运用(5滩、10滩)方案能在滞洪沉沙功能和减灾效应之间取得更好的平衡,可作为未来滩区优化运用的决策参考。     

Channel response to sediment replenishment in a large gravel‐bed river: The case of the Saint‐Sauveur dam in the Buëch River (Southern Alps,France)

The Saint‐Sauveur dam was built in 1992 in the middle section of the Buëch River. Downstream of the dam, a channel incision by several meters was observed. A gravel replenishment operation was planned in order to restore the active channel. An equivalent of two times the mean annual bedload‐transport capacity (43,500 m³) was replenished downstream of the dam in September 2016. The aim of this paper is to quantify morphological change associated with sediment remobilization in order to evaluate the efficiency of the restoration works. The monitoring was based on a combination of (a) change detection using sequential high‐resolution digital elevation models (from airborne LiDAR data), (b) bedload tracing using active ultrahigh‐frequency radio‐frequency identification technology, and (c) complementary field surveys of channel grain‐size distribution and morphology for bedload‐transport computation. Field monitoring allows us to capture a net aggradation along a 2‐km reach after the first post‐replenishment flood. A sediment balance analysis was performed to back‐calculate bedload supply coming from the sluicing operation during the flood. Although the sediment replenishment operation clearly had a positive impact on the morphological conditions of the starved river reach, the effective bedload supply from artificial berms (22,650 m³) was insufficient to initiate substantial channel shifting along the restored reach and a subsequent amplification of the sediment recharge. The combination of high‐resolution topographic resurveys and sediment tracing was successful to evaluate the downstream propagation of sediment replenishment effects.     

渭河中下游河道2009年过洪能力分析

在对2009年3月中游监测断面测量成果和下游汛前断面测量成果分析的基础上,通过典型断面水位流量关系的修订和滩面高程、堤防状况的进一步复核,采用曼宁公式水力因子,分析计算中下游各河段相应的河道过洪能力,并按水位~流量关系法进行了验证,结合历年防汛抢险工作的实际情况,综合分析确定了2009年渭河中下游各河段河道过洪能力为:宝鸡河段4 200 m3/s,杨凌、咸阳、西安河段5 300 m3/s。该成果为2009年渭河中下游防汛预案编制的依据,并对防汛抗洪抢险工作有重要参考价值。