Floodplain Inundation Research Articles

The Effect of Flooding and Drainage Duration on the Release of Trace Elements from Floodplain Soils

Floodplains downstream of urban catchments are sinks for potentially toxic trace elements. An intensification of the hydrological cycle and changing land use will result in floodplains becoming inundated for longer durations in the future. We collected intact soil cores from a floodplain meadow downstream of an urban catchment and subjected them to an inundation/drainage cycle in the laboratory to investigate the effect of flood duration on trace element concentrations in the soil porewater. The porewater concentrations of Ni, Cr, and Zn increased, whereas Cu and Pb decreased with flood duration. All the Cr present in porewaters was identified as Cr(III). Copper concentrations increased after drainage but Pb mobility remained suppressed. Both pH and dissolved organic carbon (DOC) increased with flood duration but were lower in treatments that were drained for the longest duration (which were also the treatments flooded for the shortest duration). The porewater concentrations of Cr and Ni decreased after drainage to levels below those observed before inundation, mirroring the DOC concentrations. We concluded that the duration of floodplain inundation does have an influence on the environmental fate of trace elements but that flooding does not influence all trace elements in the same way. The implications of an intensification of the hydrological cycle over the coming decades are that floodplains may become a source of some trace elements to aquatic and terrestrial ecosystems. Environ Toxicol Chem 2020;39:2124-2135. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Scale‐Free Structure of Surface‐Water Connectivity Within a Lowland River‐Floodplain Landscape

AbstractLowland rivers regularly flood and create complex inundation patterns where energy and matter are exchanged between landscape patches over a dynamic network of surface‐water connections. Scale‐freeness of networks for phenomena in many disciplines have been studied with mixed results. Here we present the first documented example of a (roughly) scale‐free network of surface‐water connections within a river‐floodplain landscape. We accomplish this by simulating 23 inundation maps across the historical range of flows for the Mission River in Texas. We then analyze the topology of the surface‐water connections between the river and two habitat patch types. Results show that surface‐water connectivity is scale‐free for ≥64% of simulated flows (≥70% for flows with floodplain inundation). Moreover, the dynamic surface‐water connections meet five of the six conceptual criteria of scale‐free networks. Our findings indicate that river‐floodplain landscapes are self‐organizing toward scale‐free surface‐water connections among patches that optimizes energy and matter exchange.

Assessment of the functional performance of lowland river systems subjected to climate change and large-scale morphological trends

ABSTRACT Worldwide, rivers provide important socio-economic and environmental functions and are essential to human well-being. The growing demand of user-functions and the change in river conditions due to large-scale morphology and climate change, increase the pressure on lowland river systems (e.g. Rhine, Meuse, Danube and Mississippi). To ensure a multi-functional river system, challenges related to uncertain exogenous trends should be tackled. This asks for an integrated approach that accounts for large-scale system behaviour rather than a sectorial approach. This paper proposes a framework that provides support to the river management decision-making process by assessing policy-options against uncertain exogenous processes based on the quantified performance of river functions. Hence, a case study of the Dutch Rhine was carried out, proposing a set of models to simulate river conditions and quantify the performance of the river functions navigation, nature and flood protection. The framework quantifies and monetized the impact of climate change and morphology on the user-functions in 2050. The application of the framework reveals a reduction of shipping efficiency, reduction of floodplain inundation and an increase in flood level. The monetization of river functions allowed an optimization of the policy-options, while dealing with uncertain processes as climate change and morphological changes. We demonstrated the merits of the assessment framework with a case study for the Dutch Rhine, as it provides useful quantitative information to support to decision-making in integrated river management.

How Simulations of the Land Carbon Sink Are Biased by Ignoring Fluvial Carbon Transfers: A Case Study for the Amazon Basin

Summary Land-surface models are important tools for simulation of the past, present, and future capacity of terrestrial ecosystems to absorb anthropogenic CO2 emissions. However, fluvial carbon (C) transfers are presently neglected in these models. Using the Amazon basin as a case study, we show that this negligence leads to significant underestimation of the net uptake of atmospheric C while terrestrial C storage changes are overestimated. These biases arise from the fact that C—in reality, leached from soils and exported through the river network—is instead represented as partly being respired and partly being stored in soils. Moreover, these biases scale mainly to the fluvial C export to the coast, despite aquatic CO2 emission to the atmosphere being the major pathway of riverine C exports. We further show that fluvial C transfers may change significantly in response to changes in either hydrology or in atmospheric C uptake by vegetation.

Modelling the Inundation and Morphology of the Seasonally Flooded Mayas Wetlands in the Dinder National Park-Sudan

Understanding the spatiotemporal dynamics of surface water in varied, remote and inaccessible isolated floodplain lakes is difficult. Seasonal inundation patterns of these isolated lakes can be misestimated in a hydrodynamic model due to the short time of connectivity. The seasonal and annual variability of the Dinder River flow has great impact on what is so called Mayas wetlands, and hence, on the habitats and the ecological status of the Dinder National Park. This variability produces large morphological changes due to sediment transported within the river or from the upper catchment, which affects inflows to Mayas wetlands and floodplain inundation in general. In this paper, we investigated the morphological dimension using a quasi-3D modelling approach to support the management of the valuable Mayas wetlands ecosystems, and in particular, assessment of hydrological and morphological regime of the Dinder River as well as the Musa Maya. Six scenarios were developed and tested. The first three scenarios consider three different hydrologic conditions of average, wet and dry years under the existing system with the constructed connection canal. While the other three scenarios consider the same hydrologic conditions but under the natural system without an artificial connection canal. The modelling helps to understand the effect of human intervention (connection canal) on the Musa Maya. The comparison between the simulated scenarios concludes that the hydrodynamics and sedimentology of the Maya are driven by the two main factors: a) the hydrological variability of Dinder River; and b) deposited sediment plugs in the connection canal.

Basal resource quality and energy sources in three habitats of a lowland river ecosystem

AbstractUnderstanding energy flow through ecosystems and among sub‐habitats is critical for understanding patterns of biodiversity and ecosystem function. It can also be of considerable applied interest in situations where managing for connectivity among habitats is important for restoring degraded ecosystems. Here, we describe patterns of basal resource quality and identify primary basal energy sources in three habitats—river channels, anabranches and wetlands—of a lowland river floodplain in the Murray River catchment, Australia during a period of disconnected surface flow. We used a combination of stable isotope and fatty acid analyses to determine which basal resources were assimilated by the backswimmer Anisops thienemanni and the Eastern mosquitofish Gambusia holbrooki and assessed food quality across the three habitats. Seston was a primary basal resource for both animals in all three habitats, but was of higher quality within floodplain habitats than in the river channel. Although floodplain seston contained higher concentrations of essential fatty acids, fatty acid profiles of animals from different habitats remained similar. Our research suggests that inundation of floodplains and subsequent reconnection to the river could be valuable to afford riverine animals the opportunity to access high quality resources, but highlights a need to quantitatively assess the transfer of essential fatty acids between trophic levels to determine how much riverine animals are in fact limited by poorer quality food resources. We demonstrate the importance of estimating the quality of organic matter fluxes into food webs, and the potential role of targeted environmental flows to re‐establish high quality energy pathways in riverine ecosystems.

Floodplain Inundation and Salinization From a Recently Restored First‐Order Tidal Stream

AbstractThe systematic response of coastal ecosystems to inundation and salinity exposure is fundamental to their ecology and biogeochemical function. Here we observe and model freshwater‐seawater interactions in a first‐order stream—floodplain system where tidal access was recently restored. Subsurface flow and transport modeling were used to quantify and better understand the interplay of processes, properties, and conditions that control water level and salinity in the floodplain to the tidal stream. Water levels in the stream were highly correlated with tidal forcing, which resulted in episodic inundation of the floodplain at quasi‐monthly frequency. The tidal stream is the only source of salinity to the floodplain, yet shallow groundwater salinity was considerably higher than average stream salinity. The low‐permeability clay floodplain soils limit lateral groundwater flow and transport, resulting in floodplain groundwater and salinity dynamics driven almost exclusively by infiltration during inundation events. As inundation occurs during high tide, estuarine waters reach the floodplain with minor attenuation in salinity from the stream's freshwater discharge. Infiltration and salinity exposure are topography controlled and regulated by ponding depth and duration, seasonal ground saturation, and depth to water table. The model suggests that floodplain salinity is currently in an early stage of transition from pre‐restoration freshwater conditions and will not reach equilibrium for ~20 years. These findings have broad relevance for understanding how and over what time scales coastal ecosystems will respond to increasing seawater exposure from sea level rise, ocean‐originating storms, and changes in natural and man‐made barriers.

Predicting hot spots of aquatic plant biomass in a large floodplain river catchment in the Australian wet-dry tropics

Conservation planning processes and wetland management require spatial estimations of aquatic habitats to support the maintenance of aquatic biodiversity. However, physical access to several wetlands and freshwater habitats can be restricted due to difficult topography and technological limitations associated with ground-based observations. In addition to these constraints, the distribution of some aquatic primary producers in freshwater habitats and floodplains that are difficult to reach further complicates large-scale assessment of aquatic habitats using traditional field-based techniques. The main objective of this study is to predict the spatial distribution of hot spots of primary producers (aquatic plant biomass) and assess large-scale inundation patterns in a large floodplain wetland (Flinders catchment) in the wet-dry tropics of Australia. To this end, remote sensing biophysical indicators (vegetation and inundation) were integrated with flood water depth in a classification tree model. Results indicate that in terms of floodplain total inundation, the Flinders wetland hydrology is rather restricted immediately after the summer wet season, the period when most primary production happens. While this can be attributed to the fact that much of the observed annual variability (93%) in rainfall and surface runoff (95%) occur during the wet season, post flood recession patterns are indicators that underpin the somewhat limited alimentation of the Flinders floodplain during this period. As observed in this study, post flood inundation extents in the summers of 2009 and 2019 declined by approximately 89% and 87% within fourteen and ten days, respectively. Despite having a significantly higher magnitude than the 2009 summer flood event, the 2019 extreme ‘big wet’ period did not translate to higher floodplain productivity (aquatic plant biomass and surface water distribution) immediately after summer as was the case in 2009. Furthermore, the predicted extents of aquatic plant biomass and total floodplain inundation in the downstream Flinders show substantial temporal variation and suggest the floodplain wetland hydrology is largely driven by inter-annual changes in annual rainfall. The extents of these hot spots of biomass accumulation were found to be considerably associated with total floodplain inundation extent (r=0.94), rainfall (r=0.81), and discharge (r=0.68). Furthermore, advance statistical analyses show that downstream discharge and rainfall over the Flinders are significantly correlated (r=0.72). In addition to this, observed amplitudes of discharge and rainfall in extreme wet and dry years coincided with floodplain inundation patterns and distribution of hot spots of primary producers. While these relationships emphasize the importance of flow in the nourishment of the downstream catchment, they further corroborate the composite influence of local rainfall and discharge on total floodplain inundation and hot spots of primary producers.

Climate change and dam development: Effects on wetland connectivity and ecological habitat in tropical wetlands

AbstractWetlands are one of the most threatened ecosystems on earth. Globally, there is growing demand to develop infrastructure to harvest water resources to support agriculture, threatening the ecological integrity of associated wetland ecosystems. We investigated the potential ecological impacts on floodplain wetland connectivity in northern Australia in response to changes in flow regime due to dam construction and climate change. Results for this study indicate that a drier climate and/or dam construction in catchments have the potential to reduce the effective size of the floodplain and reduce wetland connectivity. A drier climate will reduce rainfall and subsequent catchment run‐off, resulting in a decrease in the magnitude of riverine flows. In contrast, dams in the upper catchment will reduce the magnitude of flows downstream. The reduction in flows under both dam development and a drier climate will result in reduced extent and duration of floodplain inundation and decreased wetland connectivity. As a result, we anticipate that this loss of connectivity will reduce the capacity for nutrients, carbon and primary production to be flushed into the river channel, as well as reduce the ability for biota such as fish and turtles to move between in‐channel and off‐channel habitats.

Hazardous Ice Phenomena In Rivers Of The Russian Arctic Zone Under Current Climate Conditions And The Safety Of Water Use

The ice regime of the Russian Arctic rivers and its hazardous manifestations under current climate conditions are characterized. The ice phenomena in rivers in the region determine the conditions of navigation, water supply, hydropower station (HPS) operation, and the construction of temporary ice bridges and roads. Data of more than 100 hydrological gages over period from 1936 to 2016 were used to compile various cartographic materials and to analyze the spatial variations of the dates of ice phenomena, the duration of ice-free and ice cover periods, and the maximal ice thickness. Special attention is paid to the characteristics of level regime in periods with ice phenomena. Data on the frequency of floodplain inundation during spring ice run, the hazard of ice jams, and the seasonal features of the passage of maximal annual water level are generalized.The observed changes in ice regime characteristics and ice hazard are analyzed. The years of the start of statistically significant shift of the periods of ice phenomena, caused by both climate changes and anthropogenic impact, are identified. The increase in the duration of the ice-free period was found to be not greater than 3–4 days for East Siberian rivers, 5–6 days for the Middle and West Siberian rivers, and up to 10–12 days for the rivers in the European part. A decrease in the maximal ice thickness is most pronounced in the rivers of the Northern European Russia, where it is 10–15 cm. The frequency of floodplain inundation during spring ice run remains constant.

River food chains lead to riparian bats and birds in two mid‐order rivers

AbstractRiver regulation can modify natural flow regimes with deleterious effects on aquatic communities. While the effects of flow manipulation on the physical environment and populations and assemblages of aquatic organisms have been described thoroughly, how and to what extent river regulation influences ecosystem processes like food web architecture is less studied. Emergent aquatic insect prey can provide an important food resource to riparian consumers like birds and bats with concomitant consequences for nutrient cycling through aquatic–terrestrial food webs, thus potentially increasing the spatial influence of river regulation into the riparian zone and beyond. We used naturally abundant stable isotopes of carbon and nitrogen to compare food web architecture (trophic position and reliance on an aquatic nutritional pathway) leading to birds and bats between a regulated river, the Tuolumne River downstream of Hetch Hetchy Reservoir, and an adjacent unregulated river, the Merced River, located in Yosemite National Park on the west slope of the Sierra Nevada, California, USA. We found that both birds and bats derived >50% of their nutrition from food webs originating in photosynthesis by algae. In addition, birds and bats occupied a similar trophic position to predatory fish in other systems. Both birds and bats seemed to rely more strongly on an aquatic nutritional pathway during the dryer year of our study period, underscoring the potential importance of emergent aquatic prey as a water subsidy in dry systems and in dry years. In the Tuolumne River, reservoir managers strive to simulate characteristics of the natural flow regime, including seasonal scouring flows and prolonged floodplain inundation. Although we found no conclusive evidence of an effect of river regulation on food web responses, our study suggests that nutrient cycling through aquatic–terrestrial food webs expands the potential influence of river regulation to organisms and ecosystems typically characterized as terrestrial.

Seasonal evaluation of biotic and abiotic factors suggests phosphorus retention in constructed floodplains in three agricultural streams

Floodplain restoration constructed via the two-stage ditch in agricultural streams has the potential to enhance nutrient retention and prevent the eutrophication of downstream ecosystems. Identifying the role of biotic and abiotic factors influencing soluble reactive phosphorus (SRP) retention in floodplains is of interest given that changing redox conditions associated with floodplain inundation can result in a release of geochemically sorbed SRP to the water column. In three agricultural waterways (Indiana, USA), we conducted seasonal measurements of a suite of biogeochemical pools (total P, bioavailable P and Fe) and processes (SRP flux and microbial respiration) from multiple floodplain transects, along with their adjacent stream sediments, to determine the role of biotic and abiotic processes on floodplain SRP retention or release. Across floodplain soils, organic matter explained a significant amount of variation in soil respiration, and SRP flux from the water column to the floodplain soils was driven by the molar ratio of Fe: P, with values >6 indicating potential SRP sorption due to increased available sorption sites. We developed a mass balance model at a single site to relate seasonal floodplain processes with water column SRP export, above and below the study reach, using measurements in this study combined with data from the literature. Grab sample data suggest that the reach retained 26% of incoming SRP, which the mass balance model attributed to seasonal synergy between plant assimilation in spring and summer (removing P from floodplain soils) and abiotic P sorption during winter and spring inundation (adding SRP to the floodplain). Retention of SRP was higher in floodplain soils compared to stream sediments based on the modeled SRP budget. Thus, we suggest that these constructed floodplains will maximize SRP retention from the water column if they inundate regularly, have floodplain soils with Fe:P > 3–6, and that promote sustained plant life.

Using Remote Sensing to Assess Alligator Gar Spawning Habitat Suitability in the Lower Mississippi River

AbstractFloodplains are an important part of large‐river ecosystems; the frequency, timing, duration, and spatial extent of inundation drive habitat quality and determine the suitability of these habitats for both aquatic and terrestrial organisms. Managers have traditionally had very limited information with which to evaluate and quantify the dynamics of large‐river floodplains. Alligator Gar Atractosteus spatula use floodplains in the lower Mississippi River for spawning and have experienced declines in historic range that have been partly attributed to declines in spawning habitat availability. The Alligator Gar has therefore been identified by the American Fisheries Society, the U.S. Fish and Wildlife Service, and many state agencies as a species of concern in the lower Mississippi Alluvial Valley. The goal of this study was to develop landscape‐level spatial data to determine the extent and quality of floodplain habitat that may be available for Alligator Gar spawning. Multi‐temporal analysis of remote sensing imagery was used to develop spatial data products that defined floodplain inundation extent, inundation frequency, and temperature. These products were combined with existing layers of physical habitat structure to define and quantify spawning habitat suitability throughout the entire area subject to direct inundation by the lower Mississippi River. Habitat suitability categories were defined based on meeting unique combinations of inundation, temperature, and physical structure so that the most suitable conservation measures can be applied to improve local conditions.

English

Abstract Anthropogenic modifications to river-floodplain systems can decouple floodplains from mainstem inputs, alter flood pulse dynamics, and disrupt population dynamics and trophic web stability of aquatic biota. The Atchafalaya River Basin (ARB) receives an annual flood pulse from the Mississippi River that contributes to high crayfish abundance. Conversely, reduced crayfish abundance in the Barataria Basin (BB) is attributed to the system no longer receiving an annual flood pulse from the Mississippi River. Therefore, the purpose of this research was to determine if the absence of an annual flood pulse and reduced crayfish abundance influenced the diets of carnivorous fishes by examining stomach contents of fishes from both basins. Stomach contents were grouped as crayfish, fish, non-crayfish invertebrate, and herpetological. Although the percent occurrence of crayfish in fish stomachs differed between floodplain inundation and low-water periods in the ARB, crayfish were still the major diet constituent of ARB fishes during both periods. Non-crayfish invertebrate was the major diet constituent in BB fishes, with crayfish ranking as the second fewest diet constituent present. Our results demonstrate how flood pulse dynamics influence crayfish, and ultimately trophic webs, in large river-floodplain systems.

Managed floodplain inundation maintains ecological function in lowland rivers

Managed environmental flows are one mechanism by which managers may restore carbon dynamics, diversity and ecological function of rivers affected by anthropogenic activities. Empirical studies that quantify such interactions in detail are few, so we measured the amounts of dissolved organic carbon, nutrients, algae and invertebrates in the main river channel following a managed environmental flow that inundated an adjacent floodplain forest. Dissolved organic carbon (DOC), seston carbon, total nitrogen (TN), and chlorophyll-a (chl-a) concentrations were greatly increased downstream. The net yield of DOC, seston carbon, TN and chl-a from the floodplain peaked at approximately 100, 50, 5 and 0.1 t d−1, respectively during the major flow event. Total phosphorus mobilisation peaked at approximately 0.4 t d−1. Stable isotope analysis showed that allochthonously-derived carbon was rapidly incorporated into biofilm and grazing macroinvertebrates, persisting in riverine food webs for up to four months following the flood. During a subsequent smaller flow event, the floodplain either generated no further carbon or nutrients, or was a sink for carbon and nutrients. Our results provide empirical support for the River Wave Concept and show that allowing floodplain water to return to the river downstream of forests is important for maintaining ecological function within the river channel.

Satellite-derived changes in floodplain productivity and freshwater habitats in northern Australia (1991–2019)

Abstract The ecological communities supported by freshwater habitats and wetlands that persist from floodplain inundation generate numerous cultural, recreational and economic values via commercial fisheries and other human uses of these habitats. However, the alteration of flow connectivity, degradation, and disruption of physical processes that sustain different levels of organisms (e.g., primary producers) are threats that affect aquatic biodiversity and the productivity of these habitats. Therefore, the large scale assessment of freshwater habitats for proactive water resources planning and the development of climate change mitigation and resource management strategies is essential. However, such monitoring and assessment is complicated by the inaccessibility of many large wetland systems during times of inundation, making in situ sampling unfeasible at a time when high levels of aquatic primary producers are generating food and energy sources for higher order consumers. To understand the physical dynamics of aquatic primary producers and freshwater habitats (1991–2019) during such times in a large floodplain river in northern Australia (Gilbert catchment), this study integrated Landsat-derived modified normalised difference water index and normalised difference vegetation index in a classification tree model. Thereafter, key hydrological drivers (rainfall and river discharge) of floodplain productivity and connectivity were assessed using a range of multivariate techniques. Results show that the floodplain had a high aquatic plant biomass during the summer wet season based on the correlation between aquatic biomass accumulation (hot spots) and inundation ( r = 0.83 @ phase lag r = 0.68 @ lag = 1 month) at downstream Gilbert catchment appear to be a relatively stronger indicator of hot spots of floodplain biomass accumulation as opposed to local rainfall ( r = 0.57 @ lag = 3 months). While the downstream discharge explains a significant proportion of variability in the leading orthogonal mode of rainfall ( r = 0.83 ), statistical relationships developed between discharge/rainfall and the distribution of aquatic primary producers confirm that both rivers (flow) and local rainfall are key optimal predictors of inundation and sites of primary producers with river flows being a better indicator of the latter. It is therefore argued that hydro-meteorological fluctuations will be key constraints on freshwater habitats and the growth of primary producers, albeit, human disturbance of flow can impact on floodplain productivity. As illustrated in this study, such constraints are reflected in the spatial patterns and changing characteristics (connectivity and spatial heterogeneity) of hot spots of primary producers and freshwater habitats (Palustrine, Lacustrine, and Riverine ecosystems).

Flood mapping using hydraulic modeling and Sentinel-1 image: Case study of Medjerda Basin, northern Tunisia

In northwestern Tunisia, floods are the most widespread natural hazard. Indeed, this problem is posed seriously in the Medjerda basin. In fact, the plain of Jendouba - Bou Salem is the most affected area by this plague. It has the form of a shallows that collects runoff water and promotes flood extent and duration. So the main objective of this study is to determine the extent of the hydraulic hazard through the flood mapping of February 2015 event which has seriously affected the urban and peri-urban landscape of the plain. The hydraulic hazard extent mapping was determined through the HEC-RAS model. It's one of the most popular free hydraulic models developed by the Hydrological Engineers Center of the U.S. Army Corps. The new version (HEC-RAS v-5) is a two dimensional (2D) model based on the resolution of hydraulic Saint Venant which can simulate floodplain inundation, determine the water surface elevation and velocity distribution of floods. It allows modeling flow with permanent and non-permanent free surface by evaluating water flows and heights over the all sections of a river so it allows to integrate hydraulic works (bridge, dam …).The result showed that this flood reached heights of more than six (6) meters in flooded areas. The result from the HEC-RAS model was validated using the Sentinel-1 radar image acquired on February 28th, 2015.The study shows the applicability and the capabilities of the 2D HEC-RAS version for flood studies.

On the Hydrodynamic Behavior of the Changed River–Lake Relationship in a Large Floodplain System, Poyang Lake (China)

Poyang lake floodplains are hydrologically complex and dynamic systems which exhibit dramatic intra-annual wetting and drying. The flow regime of the Yangtze River was previously known to play an important role in affecting Poyang Lake and its extremely productive floodplains (river–lake relationship). The recent severe declines and recessions in the lake are closely linked to the changed river–lake relationship, resulting in significant hydrological, ecological, and economic problems. This study aims to examine the spatiotemporal heterogeneity of the floodplain hydrodynamic behaviors with respect to impacts of the changed river–lake relationship, characterized by the lake water level, inundation area, and inundation duration based on a floodplain hydrodynamic model of Poyang Lake, and to further quantify the severity of dryness recently endured since 2000. Simulation results show that, in general, the current modified river–lake relationship is more likely to affect the hydrological seasonality of the floodplain system since 2000, relative to the flooding and drying cycles during past decades (1953–2000). The present hydrodynamic behaviors suffered significant change due to the greatest interference from the altered river–lake relationship, particularly for the falling period in October. On average, the floodplain water level and inundation duration decreased by 6 m and 12 days during October, respectively. Additionally, the highest monthly shrinkage rate in floodplain inundation shifted from the period of October–November to September–October, with the mean inundation area decreasing by around 50%, demonstrating an advanced and prolonged dry condition. The spatial responses of the hydrodynamics in the low-slope floodplains are most likely to be affected by the dynamic river–lake relationship, as expected. This study assessed the effects of the altered river–lake relationship on the hydrological regime of the Poyang Lake floodplains in terms of spatiotemporal distributions and changing processes for the periodic inundated behavior, which can support the relevant study of the subsequent ecological effects on the wetlands.

Estimation of the Environmental Flow Regime to Deter-mine the Minimum Flow for Pollution Reduction: Wadi Zomar - Palestine as a Case Study

Possible factors that play a role in restoring a flow regime that supports a healthy environment were identified for Wadi Zomar, Palestine. The hydrograph shows that threshold discharges for bed drying are less than 0.14 m3/s, bar formation is less than 0.4 ms/s and floodplain inundation events are over 3 m3/s. The HEC-RAS model suggests a continuous discharge throughout the year that maintains the base flow in the range of 0.5 m3/s. The model suggests that the restoration process is controlled by two main factors: role of sufficient flow and flood inundation frequency

Estimation of the Environmental Flow Regime to Deter-mine the Minimum Flow for Pollution Reduction: Wadi Zomar - Palestine as a Case Study

Possible factors that play a role in restoring a flow regime that supports a healthy environment were identified for Wadi Zomar, Palestine. The hydrograph shows that threshold discharges for bed drying are less than 0.14 m3/s, bar formation is less than 0.4 ms/s and floodplain inundation events are over 3 m3/s. The HEC-RAS model suggests a continuous discharge throughout the year that maintains the base flow in the range of 0.5 m3/s. The model suggests that the restoration process is controlled by two main factors: role of sufficient flow and flood inundation frequency