Effect of spring flood onto vertical Distribution of soil invertebrates in Near-channel floodplain of the Samara River

Drylands occupy about one-third of the world's land surface area and rivers in these regions have less predictable flow regimes than those in humid tropical and temperate regions. Australia's dryland river-floodplain systems cycle through recurrent periods of floods and droughts, oflen resulting in extreme hydrological variability. As a result, these systems have been described as having a 'boom and boost' ecology with periods of high productivity associated with flooding. Not surprisingly, flow and its variability have been recognised as major driving forces in the ecological functioning of Australian rivers and responses to flow variability from fish and aquatic invertebrates have been reasonably well described. Furthermore, the reduced amount of water reaching floodplain waterbodies due to river regulation has been held responsible for successional changes in aquatic biota and, consequently, the resources available for both fish and invertebrates. However, information regarding the impacts of water resource development has generally focused on within-channel processes of Australian rivers, not on floodplains, which are arguably more affected by water development. The following dissertation is concerned with how different types of natural and modified floodplain lagoons are able to trophically support their fish communities in the floodplain of the Macintyre River, Border Rivers catchment (QLD/NSW), a regulated dryland river. This study focuses on the influence of flooding and the implications of an extended dry period, and different levels of flow regulation, on the feeding ecology of selected fish species (Ambassis agassizil, Lelopotherapon unicolor and Nematalosa erebi) between 2001 and 2003. Food resources consumed by fish are hypothesised to vary in response to flooding, when inundation of isolated lagoons and vast floodplain areas can result in a burst of primary and secondary productivity. Given the permanently elevated water levels of some regulated floodplain lagoons, fish diets are hypothesised to be less variable in these floodplain habitats in comparison to diets of fish from floodplain lagoons with natural flow and water regime. Feeding ecology is examined firstly, in terms of diet composition of selected fish species, using stomach content analysis, and secondly, in relation to possible energy sources sustaining fish (using stable isotope analysis) in selected floodplain lagoons and a site in the main channel of the Macintyre River. The information produced should allow managers to take variations in food resources, food web structure and dietary ecology into account in management regimes for refugia and dryland systems in general. Factors such as diel and ontogenetic variations in dietary composition and food intake by fish are shown to considerably affect ovemll dietary patterns of each study species. Therefore, it is important to understand the contributions of such factors to the variability of fish dietary patterns before performing studies on resource use by fish in floodplain habitats of the Macintyre River. Major food categories consumed by the study species were zooplankton, aquatic invertebrates and detrital material. Zooplankton was of particular importance as this food item was ingested by all three study species at some stage of their life history. Spatial and temporal variation in diet composition of the study species was mostly associated with changes in prey items available across floodplain habitats and between seasons (summer/winter). The low magnitude of flooding events during the study period is arguably the most likely factor influencing the lack of patterns of variation in fish diets in floodplain habitats subject to flooding, whereas in non-flooded lagoons the observed dietary variation was a consequence of successional changes in composition of the aquatic fauna as the dry season progressed. Water regime had an important effect on differences in fish diet composition across lagoons, but further evaluation of the influence of flooding is needed due to overall lack of major flooding events during the study period. Autochthonous resources, namely plankton, were the basis of the food web and phytoplankton in the seston is the most likely ultimate energy source for fish consumers, via planktonic suspension feeders (zooplankton). Nevertheless, organic mailer could not be disregarded as an important energy source for invertebrates and higher consumers. In general, the present study does not provide support for the major models predicting the ftinctioning of large rivers, such as the River Continuum Concept and Flood Pulse Concept, which argue that allochthonous organic matter either from upstream or from the floodplain are the most important sources of carbon supporting higher consumers. In contrast, the Riverine Productivity Model would be more appropriate to describe the food web and energy sources for consumers in the Macintyre River floodplain as this model suggests that local productivity, based on autochthonous phytoplankton and organic matter, ftiels food webs in large rivers. The results of this study suggest that factors known to affect phytoplankton production in floodplain lagoons (e.g. flow regulation, turbidity and nutrient/herbicide inputs) must be seriously considered in current landscape and water management practices.

In this study the river migration model MIANDRAS has been applied to simulations of the planform changes of the river Allier, a tributary of the river Loire in France. The Allier is a very dynamic and natural river system with braided and meandering river sections. Two meandering reaches of the Allier, located between Varennes-sur-Allier and Moulins, have been examined in the present study. MIANDRAS is a numerical model that simulates meandering processes in shallow alluvial rivers with erodible banks. In MIANDRAS the river is schematised as a single meandering channel, as the floodplains are assumed non-conveying. For the prediction of river planform changes, the rate and direction of bank erosion are computed by coupling a steady-state flow and bed topography model with a time-dependent bank erosion model. Sediment gradation, timedependent variations of the bed topography (i.e. migrating bars) and flow exchanges between the main channel and the floodplains are not taken into account. MIANDRAS did not perform satisfactorily in predicting the planform changes of the Allier. The 2(and 3-) dimensional flow processes in flood periods, caused by floodplain constrictions and flow exchange between the main channel and the floodplains, appeared to be an important feature influencing the bank erosion. Therefore, the influence of overbank flow was studied in more detail. The 3-dimensional flow model DELFT3D-FLOW (TRISULA) was used to simulate overbank flow processes in one of the examined reaches of the Allier. The results of the MIANDRAS computations can be explained reasonably well from the results of the overbank flow computations. Near the upstream floodplain constriction, where high bank erosion rates were observed in the prototype river, high velocities occurred in the overbank flow computations. At this location high bank erosion coefficients had to be adopted in the MIANDRAS computations. The relatively low erosion rates at the downstream boundary can be explained by the low velocities occurring in overbank flow. These are due to backwater effects near the downstream floodplain constriction. The small erosion rates at this location resulted in small erodibilities in the MIANDRAS computations. Floodplain bed roughness appears to have a significant influence on velocity directions and magnitudes. The velocity field is correlated to the flow exchange between the main channel and the floodplains. This flow exchange strongly decreases in the case of a higher floodplain bed roughness. These results agree with the results of scale model experiments performed in the Flood Channel Facility at HR Wallingford, England. The results of this study give new indications for the range of applicability of MIANDRAS. Besides the possibility to use MIANDRAS in case of rivers with mainly inbank flow, the model can also be applied to rivers with overbank flow periods, provided that the flow exchange between the main channel and the floodplains is small. A small flow exchange occurs in case of a high floodplain bed roughness, a straight floodplain and main channel, or relatively small flood discharges.

از ویژگی‌های بارز رودخانه کرخه در غرب استان خوزستان به ویژه در دشت آزادگان، دینامیک فعال آن است. بررسی این پویایی و تعیین نقش آن در ایجاد مخاطرات محیطی و ساختار فضایی منطقه، مستلزم شناخت مورفودینامیک رودخانه از گذشته تا حال بر اساس شواهد رسوبی و هیدرومورفولوژی است؛ زیرا مورفودینامیک رودخانه ها به خصوص در دشت های سیلابی معلول شرایط رسوب گذاری و وقایع محیط شناسی مانند تغییرات آب و هوایی و تغییرات سطح اساس آب هاست. بدین منظور، پس از جمع‌آوری داده‌ها، تغییرات مسیر رودخانه و شرایط محیط های رسوبی به عنوان متغیر مستقل و عناصر فضایی مانند تغییر در اندازه ذرات رسوبی، تپه‌های ماسه‌ای، کاربری های کشاورزی، مسکونی و غیره به عنوان متغیرهای وابسته در نظر گرفته شدند. ابتدا با استفاده از روش‌های پردازش رقومی بر روی تصاویرماهواره ای لندست سال‌های 1990،1993،1998،2002 میلادی و سنجنده Liss از ماهواره IRS هند سال 2006 میلادی و ثبت نقاط شاخص در بازدیدهای میدانی، مسیرهای متروکه بازسازی و مسیرهای فعال بررسی شدند. در ادامه با تطبیق مسیرهای رودخانه با سایر لایه‌های اطلاعاتی، دو مغزه رسوبی در محل های رفیع و جفیرتا عمق 10 متری به منظور تعیین رابطه بین قطر ذرات رسوبی با شرایط سیلابی و محیط های رسوب گذاری گرفته شد. نتایج نشان داد، سه توالی رسوبی با شرایط اقلیمی مرطوب و کاهش قطر ذرات رسوبی در اعماق(10-6، 5-4، 3-0 متری) و دو دوره با شرایط اقلیمی خشک به همراه افزایش قطر ذرات رسوبی در اعماق( 6-5 و 4-3 متری) را می توان در مغزه ها تشخیص داد. شرایط اقلیمی خشک به همراه عقب‌نشینی خط ساحلی در هولوسن میانی سبب شد، دلتای کارون و کرخه توسعه پیداکرده و جابجایی و تغییر مسیرهایی نیز در بستر این رودخانه ها پدیدار شود. این تغییرات در مسیر روستای عبدالخان تا تالاب هویزه دارای حداقل دو تغییر شکل پلان خم رودخانه و چندین مسیر متروکه طبیعی می باشد. به دلیل سرعت و تنش برشی، خم‌ها با پدیده انتقال وگسترش همراه بوده‌ و ضمن ایجاد خسارت به اراضی کشاورزی و مسکونی، موجب جابجایی آن ها نیز شده است.

The Effects of Floods on Estuarine Fisheries and Food Webs

The Lafa River Basin (LRB) experiences increased frequency and magnitude of floods, causing increases in areal and depth of inundation. This translates into huge economic losses and loss of human lives. The effective management of flood disaster of the LRB is hinged on the identification of the factors responsible for the floods, modelling of the flood situations and a quantitative assessment of the hazard zones. Hydrologic Engineering Centre-Hydrologic Modeling System (HEC-HMS) and Hydrologic Engineering Centre-River Analysis System (HEC-RAS) models have been integrated with Geographical Information System (GIS) to identify the driving forces behind the floods, and assess the hazard zones of the Basin. Physiographical characteristics are responsible for the floods and analysis indicate that the LRB is a small urbanised elongated drainage basin of area 27.945 km2 with predominantly steep slopes, and impervious surface soils. The Peak flows produced by 2, 15, 25, 50, and 100 year return period storms have been found to inundate 233.88 ha, 292.92 ha, 298.36 ha, 305.00 ha, and 311.24 ha respectively. 1.68 %, 5.54 %, 5.91 %, 6.41 %, and 6.63 % respectively of total inundation areas were above inundated depth of 2 m and are located around culvert locations on the Lafa stream. Keywords-Basin, Flood plain, Hydrological analysis, Modelling, Peak flows

Many rivers in Nigeria had been ungauged in the last three decades; this worrisome scenario has impacted negatively on the livelihood of people who live in flood plains. The general lack of up to date streamflow data has made river basin management problematic especially in the area of flood risk management and the development of a real time flood warning system. Flood studies were carried out in the Ogun River Basin in the southwest Nigeria using synthetic data generated by Rainfall-Runoff Modeling using a combination of the Natural Resources Conservation Service (NRCS) curve number model and digital terrain modeling using ArcGIS® 9.3 software to identify vulnerable areas in relation to synthesized flood waves generated from the basin, extent of inundation and ranking of the flash points that was equally done using proximity to hazard source as a criteria. The total area in the basin covered by fresh water swamps, salt marsh, and tidal flats at the lower course of Ogun river is 49 km2, while the spatial extent of the entire wetland is 556 km2 accordingly. When a peak flood volume of 4 270 million m3 generated in September is routed into the fresh water swamp, about 33.4 m of flood depth was left unaccommodated, which will cause inundation of the entire flood plain and severe damage on its path. Over 1.4 million inhabitants were identified to be at risk in the area. When the entire wetland was considered, the flood wave was reduced to an average depth of 8.5 m which is still capable of causing grave damages in the remaining parts of the flood plain. The flood wave was found to have a residence time of about 45 days. Appropriate recommendations were given for practical adaptations.

The changes to catchment scale flood risk following river restoration works, including the addition of large wood logjams to the channel, are poorly quantified in the literature. Key concerns following river restoration for river managers and other stakeholders are changes to flood hydrology at the reach and catchment scale and changes in the mobility of large wood pieces. The effects of accumulations of large wood (logjams) on local flood hydrology have been documented in the literature, showing logjams slow flood wave travel time and increase the duration and extent of local overbank inundation. Modelling studies conducted at a reach scale have shown that these local effects can slow flood wave travel time through a reach and delay the timing of flood peak discharge at the reach outflow. How these local and reach scale effects translate to the catchment scale remains to be illustrated in the literature. In this thesis a combination of field and modelling studies are used to; elucidate the link between logjam form and function, to quantify the mobility of pieces of large wood relative to their physical characteristics, to predict the changes in floodplain forest restoration over time and to provide predictions of changes to catchment scale flood hydrology following river restoration at a range of scales and locations. It is shown that logjams inducing a step in the water profile are most effective at creating diverse geomorphology and habitats. Logjams were found to account for 65% of flow resistance in forested river channels, rising to 75-98% of flow resistance where the logjam was inducing a step in the water profile. Large wood in small forested river channels was found to be highly mobile with 75% of pieces moving, with the longest transport length of 5.6km. Large wood mobility is governed primarily by the length of a piece of wood with wood in excess of 1.5x channel width a threshold for a lower probability of movement. Hydrological modelling using OVERFLOW shows that reach scale river restoration can lead to modest changes in catchment scale flood hydrology. It is concluded that flood risk management can incorporate river restoration, but that results are likely to be unpredictable if engineered logjams are used alone. Substantial benefits in reducing catchment outflow peak discharge (up to 5% reduction) are modelled for floodplain forest restoration at the sub-catchment scale (10-15% of catchment area), rising to up to 10% reductions as the forest matures and becomes more complex.

The observation of surface water bodies in all weather conditions and better knowledge about inundation patterns are important for water resource management and flood early warning. Microwave radiometers at 37 GHz were applied to observe and study the inundation pattern in large subtropical floodplains in China, i.e. the Poyang Lake and Dongting Lake floodplains, due to the trade-off between the capability to penetrate hydrometeors and vegetation, revisiting time, and spatial coverage and resolution. Taking the shallow sensing depth at 37 GHz into account, open water, inundated area and water saturated soil surface all determine the surface emittance measured by the radiometer. Thus, Water Saturated Surface (WSS) is defined as the combination of these three land surface elements. In subtropical regions, seasonal changes in vegetation cover and various surface roughness conditions are the major challenges for the observation of surface water bodies with microwave radiometers. Atmospheric attenuation, observation gaps and errors in the microwave observations reduce the quality of daily radiometric observations. To deal with the attenuation due to vegetation and surface roughness, a two-step model was developed: the first step is to retrieve the polarization difference emissivity from Polarization Difference Brightness Temperature (PDBT) at 37 GHz with the simplified radiative transfer model and the vegetation optical thickness at 37 GHz parameterized from Normalized Difference Vegetation Index (NDVI) ; the second step is to retrieve the fractional area of WSS from the emissivity difference with a linear model, which can be parameterized according to the Qp surface roughness model. To remove the noise and extract the surface signal (including surface emittance and vegetation attenuation) from the daily PDBT time series, the Time Series Analysis Procedure (TSAP) was developed to identify the spectral features of noisy components in the frequency domain and remove them with a proper filter. The overall method combined the TSAP and the two-step model to derive daily observation of WSS area. The retrieved WSS area in the Poyang Lake floodplain was in a good agreement with the lake area observed from MODerate-resolution Imaging Spectroradiometer (MODIS) and Advanced Synthetic Aperture Radar (ASAR). The observations and analysis of the inundation patterns in the Poyang Lake and Dongting Lake floodplains with this method illustrated the close relationship between inundated area, precipitation and stream flow. Furthermore, a lumped hydrological model, named the discrete rainfall-runoff model, was developed to fully use the retrieved WSS area and to study the role of inundated area in stream flow production. This model simulates stream flow as the integration of contributions of antecedent precipitation in a certain period. Three implementations of the model were developed with the help of ground water table depth and the retrieved WSS area. The case study in the Xiangjiang River basin (upstream catchment of the Dongting Lake floodplain), China, illustrated that: 1) the longest duration of antecedent precipitation is a key parameter to determine model performance; 2) long duration would increase the model uncertainty and lead to overfitting; 3) the application of the WSS area can reduce the duration required to achieve a reasonable accuracy. The model parameters indicated the interaction between stream flow and various water storages, and the calibration results of three implementations implied the recharge period of ground water.

Natural and Anthropogenic Drivers of Water Quality in the Normanby Basin and Princess Charlotte Bay, Cape York Peninsula, Australia

Currently, one of the constituent parts of the Russian state policy is the sustainable development strategy, the most important element is to protect the environment (OS) from negative anthropogenic impacts. Special attention is paid to the protection of water resources, the rivers have key value in quality formation. They serve as cross-border corridors for technogenic streams of the polluting substances and deposit their considerable volumes in ground deposits. The priority polluting substances in the Republic of Bashkortostan are oil hydrocarbons (UV). Considerable sources of oil UV in OS are the enterprises of petrochemistry and oil processing. As large water consumers, they are territorially attached to a river network and pollution of the hydrosphere constitute danger. A specific type of impact of the similar enterprises on the nature is formation in soil of industrial platforms of congestions of oil UV and their further intra soil migration on adjacent territories. As a result of carrying out research works in territories of the industrial enterprises features of migration of oil pollution in flood plains of the rivers in a zone of influence of objects of the petrochemical industry are established. The industrial platforms polluted by oil products demand carrying out remediation works. Dredging of the petropolluted soil is represented inexpedient, because of the big areas and a depth of lenses to 30 meters. It is established that the petrochemical and oil processing enterprises have essential impact on environment by formation in soil of industrial platforms of congestions of oil hydrocarbons and their further migration on a land relief. Depth of penetration of oil hydrocarbons reaches 30m. Constructions for purification of the petropolluted soil by downloading in delivery wells of surfactants solutions and selection of liquid from operational wells are offered. Constructions of purification of oil-containing waters with the subsequent their reuse for soil washing are offered.

Flood risks on assets and livelihoods in tropical catchments within oil palm landscapes

Temporal variability in flow is central to the functioning of river ecosystems, with current conceptual models emphasising the importance of flow events, namely overbank flood pulses and in-channel flow pulses, in enhancing riverine fish production. However, whilst the benefits of flood pulses have been widely documented, there is an overall dearth of information with regard to the role of flow pulses in enhancing fish spawning and recruitment. To test the validity of applicable conceptual models of floodplain fish production in response to alter - nating low-flow and flow-pulse years in the absence of a flood pulse, fish larvae were sampled every three to five weeks from 2002 to 2007 in an anabranch system of the highly-regulated and semi-arid lower Murray River (south- eastern Australia). Small-bodied native fish (mainly, un-specked hardyhead, carp gudgeon, flathead gudgeon and Australian smelt) spawned successfully in every year irrespective of hydrological conditions, with Australian smelt being particularly abundant in two of the three low-flow years following a flow-pulse event. However, spawning in the majority of these small-bodied species was enhanced by the two flow pulses. On the contrary, large-bodied silver perch and golden perch only spawned during one of the two spring flow pulses, emphasising the importance of both timing and duration of a flow pulse along with its coupling with temperature. The findings of the present study support recent views that a combination of conceptual models of floodplain fish production is likely to apply in temperate to semi-arid floodplain rivers. Management measures aimed at the benefit of native fish communities should account for both flow and flood pulses through the release of environmental water, and this should be sup- ported by long-term studies able to span the components of a river's flow history.

Traditionally the Early Neolithic of the Upper Don was associated the Middle Don culture (Sinyuk, 1986), but recent researches of the following sites - Karamyshevo 5, 9; Vasilyevsky Kordon 5, 7; Ivnitsa etc. have afforded ground for attributing the Early Neolithic of the Upper Don to Karamyshevo culture. This article analyzes the finds of Karamyshevo culture from 26 sites located in the basin of the Voronezh river. Those collections have all the grounds to be included into Early Neolithic antiquities as they have gone through radiocarbon dating and their chronological position correlates with the data of Elshan, Upper Volga and other Early Neolithic Cultures. In terms of location some Karamyshevo sites can be singled out: - in the Upper Voronezh region near the settlements of Preobrazhenovka and Dobroye in Lipetsk region in the right-bank flood plain of the river on the buttes of terraces above the flood-plain and leveed banks (Vasilyevsky Kordon 3, 5, 7, 25, Ratchino 22, Dobroye 1, Studenovka 3); - in the Middle Voronezh region round Lipetsk and near the settlement of Karamyshevo in Lipetsk region in the flood plain of the river on the buttes of terraces above the flood-plain (Lipetskoye Ozero, Shlyuz, Gudovsky Kordon, Krasny Bugor, Karamyshevo 1, 5, 9, 19 etc.) - in the Lower river region on the border of Lipetsk and Voronezh regions in the left-bank flood plain of the Voronezh river on the buttes of terraces above the flood-plain (Savitskoye 1, Kurino 1, Ivnitsa, Stupino) The sites of Karamyshevo culture show some typical features which are characteristic of the Upper Don region - few stone implements, so the main distinguishing feature of those antiquities is pottery according to its finish and decoration. This pottery has lumpy paste which visually consists of natural inclusions or chamotte in rare cases. More recent pottery finds have sanded paste without visible inclusions which is similar to that of the Middle Don culture. According to the method of finishing the pottery is divided into two groups: thouroughly smoothed and burnished on the outer surface pottery and smoothed one with scratches which seems to be a definite chronological marker. According to their shape the vessels are divided into straight-walled and biconical with a straight or shaped rim and mainly with a pointed bottom. The larger part of Karamyshevo pottery is plain. So among 500 pottery finds from Ivnitsa site 62% of those materials is plain, about 20% is decorated with oval, triangle and paired strokes, 11% is decorated with a short-pitch stamp, 21 finds have thin and shallow lines on the surface and 10 finds are decorated with pits. Here we can speak about a relatively early stage of the site as later sites (Karamyshevo 9, Vasilyevsky Kordon 7) have more decorated pottery. The appearance of pit-like and comb decorations is connected with the final stage of this culture. For dating of Karamyshevo culture we have the dates of the beginning of the Vth century B.C. - the first half of the IVth century B.C. (ВР). On the basis of the above-stated data we can come to a conclusion that at the end of the IVth century B.C. the first pottery complexes appeared in the forest-steppe and forest zones of Eastern Europe and they had a number of common features which specifically formed the basis of local cultures that we single out today and which existed in the Vth century B.C. Such cultures include Karamyshevo culture which sites might have dated back to the first half of the IVth century B.C.

It has been acknowledged that river morphology and hydrology have been intensively altered due to the anthropic demands in floodplain land use and management, flood protection, promotion of navigability or energy production. Rivers were transformed in water highways, having lost contact with their surrounding floodplain as well as the plethora of ecological processes and occupants once thriving in these ecotonal zones. The identification of this emerging threat of morphological and hydrological alteration on ecological integrity adds further complexity in the exploitation of hydrosystem resources. These resources are heavily coveted and guarded by different lobbies each having strategic views on future project development. Stakeholders may want to promote hydro-electricity, ecologists a natural reserve, communes may wish to have an increased flood protection and leisure promoters a nautical center. As a result, the proposition of a river development project is certain to face opposition of one party or the other. The motivations of this dissertation are anchored in this context, where various and sometimes conflicting potentials for hydrosystem exploitation remain. This works aims at contributing scientifically to an innovative approach at the conception phase of a multi-purpose river development project by developing the ecological module to be implemented in the general project's optimizer. The SYNERGIE project hypothesis is that it should be possible to identify a synergetic pattern joining the interests of ecological integrity, flood safety, energy production and leisure development. Such a multi-objective river development project would stand more chance of acceptance. This dissertation focuses on the ecological aspects of such a river development project and an application on the regulated Swiss Upper Rhone River. Is expected an ecological answer to a river development project design / management which has to be compatible with Heller's Heller (2007) general SYNERGIE project optimizer taking into account all the project poles. The system of interest is composed of a buffering reservoir of ca. 1 km2, a run-of-the-river dam, a hydro power-plant, and an artificial river ensuring longitudinal continuum. The primary part of the work consisted in an extensive literature review on system understanding, anthropic alterations and quality assessment / prediction tool available. The approach consisted of two levels (1) the general ecological considerations to be followed at the project reservoir scale and (2) the measure of the downstream ecological response through modeling. General ecological considerations at the reservoir scale were the implementation of an artificial river ensuring longitudinal connectivity, implementation of artificial ecotonal boosters and the allocation of a sanctuary zone with limited public access. The downstream measure of ecological integrity was based on the choice of three taxonomic groups of macro-invertebrates and four ecological guilds (groups) of fish. Mayflies (Ephemeroptera), stoneflies (Plecoptera) and caddisflies (Trichoptera) richness were predicted using simple hydrological and morphological covariates (i.e. substrate, current speed,...) coupled to system specific faunistic surveys. Bank, riffle, pool and midstream fish guilds habitat values were determined using existing methods. By using the simulation results of river development project scenarios as inputs, the ecological response (i.e. the measure of ecological integrity) was computed following the assumptions that high predicted macro-invertebrate richness and high guilds habitat values were linked to a high ecological integrity. An emphasis on the hydropeaking effect in relation with river morphology was performed on macro-invertebrates. They were found to respond well to hydrological and morphological changes induced by river development projects while the approach by fish habitat value encountered limitations in its applicability. Four multi-objective project scenarios were analyzed, (1) the actual state of the Swiss Upper Rhone River at the Riddes site (VS), (2) a hypothetical hydropeaking mitigation project, (3) a hypothetical bed widening project and (4) a hypothetical bed widening coupled to hydropeakaing mitigation project. The actual state resulted in the worst measure of ecological integrity, with comparable results for hydropeaking mitigation project or the bed widening project. The highest measure of ecological integrity was observed for the coupling of hydropeaking mitigation and bed widening. These results showed that a multi-purpose project can increase the ecological integrity of the Swiss Upper Rhone River, produce electricity, provide protection from floods and develop local leisure activities. The synergetic effect of the project could be measured by project acceptance. Nevertheless, our knowledge on the hydropeaking effect on hydrosystem should still be completed by more research in order to give more weight to the ecological implication of hydropeaking.

During the last decades public awareness of the limitations of traditional engineering practices and the imperative to conserve nature have led to changes in river management; including river restoration measures. The enlargement of the fluvial corridor is one of the often considered management measures. However, the high-pressure on land-use, the conflict of interests, as well as the uncertainty of vegetation and landscape development scenarios after restoration, can make their implementation difficult. In actual decision-making processes of large river restoration projects, no dynamic long-term modelling approach of potential riparian woody species development exists mainly due to the complexity of interacting driving-processes creating lateral and longitudinal gradients. So far, forest succession models applied to riparian areas are not conceived for river areas found in Central Europe and do not address explicitly environmental influences like nitrogen scarcity or drought stress important for certain riparian systems, nor they cover integrally the vegetation-hydraulics interaction. To support and enhance the decision-making processes in river restoration projects and to provide a better understanding of riparian forest dynamics and its driving-processes, the present thesis develops a coupled model of ecological and hydraulic processes to simulate riparian forest dynamics for Central European conditions, particularly for the case of enlarged fluvial corridors. The developed model RIFOD ('RIparian FOrest Dynamics') – a distribution-based forest succession model (i.e. ecological model) coupled to a quasi-2D hydraulic model – simulates short or long-term riparian forest dynamics at a yearly time step. The model, applied on a 10 times 10 m mesh grid, is spatially-explicit concerning the interactions of the ecological and hydraulic processes and integrates 65 Central European tree and shrub species. The ecological model is based on developments of different upland forest succession models, which were improved, adapted and complemented in regard to the ecological processes in riparian areas, for example concerning regeneration, nitrogen dynamics, soil water availability or flooding stress. At the basis of the modelling of physiological flooding stress response of plants, we carried out an in-depth review of the actual knowledge of the flooding stress response of Central European tree and shrub species. The review could highlight the main biotic and abiotic factors that influence species response and revealed the broad but still vague knowledge about physiological mechanisms and species-specific data of plant response. Based on the above findings, the fuzzy set theory was chosen to model flooding stress response integrating the main abiotic factors (e.g. flooding duration, -depth). The Central European tree and shrub species were classified into flooding tolerance classes by use of clustering analysis based on proxy-data, which allowed us considering indirectly the anatomical, morphological or physiological adaptations to flooding. To model mechanical flooding stress, existing mechanistic models simulating failure resistance to uprooting or stem breakage conceived for wind load studies have been adapted to the case of water flow. Required geometrical characteristics of trees and shrubs, such as crown width and crown heights, were estimated based on available field data, whereas rooting depths in dependence of the growth stage of an individual plant were simulated by developing a quasi-mechanistic vertical root growth model for Central European tree and shrub species. This root growth model allowed also a more realistic simulation of drought stress by calculating root water extraction in relation to the development stage of stand and determining species-specific and development dependent accessibility to groundwater – not integrated in the soil water balance so far. Compared to the situation in uplands, a more realistic modelling of nitrogen availability in riparian areas could be achieved by considering the loss of nitrogen via denitrifcation, as well as the loss of litter due to flooding. In opposition to existing riparian forest succession models, RIFOD considers riparian vegetation not as a purely dependent variable of flooding. Floods may affect vegetation but they are also affected by it, owing to the contribution of vegetation to hydraulic roughness. The coupling of the forest succession model to a quasi 2-D hydraulic model allowed considering this. Moreover, the quasi steady-state model approach allowed emphasizing on the ecological relevant lateral dimension and to make the model spatially explicit in the sense of vegetation-hydraulics interaction. The current version of RIFOD finds its application in riparian areas in which the geomorphological activity of the river is not a dominant process or in case of restoration projects, for widened fluvial corridors with morphologically stable stream channels. Model evaluation (validation and sensitivity analysis) revealed that RIFOD simulates plausibly the ecological gradients observed in the field and the resulting riparian forest dynamics. By applying the model at different lateral fluvial corridor designs at the River Rhone, the consequences of a restoration measure and the change of the hydrological regime for woody vegetation could be illustrated. From a management point of view, the model revealed for example that relative benefits become smaller as the width increases or that in absence of morphological activity (e.g. lateral bank erosion) the hydraulic processes alone are not sufficient for reinitiating riparian forest succession even for high energy streams such as the River Rhone. Moreover, the model allowed verifying and discussing current scientific concepts and hypotheses, as for example the intermediate stress hypothesis. Simulation results revealed that biological diversity is highest between the very low and very severe flooding stress levels confirming the intermediate stress hypothesis involving a trade-off between competitive dominant species which monopolise stable habitats and the few fugitive species that survive high levels of instability. The value of RIFOD relies in the capacity of displaying tendencies of riparian forest dynamics and associated characteristics in function of different fluvial corridor design variants. Moreover, it allows the understanding of processes and patterns in nature by allowing exploring the consequences of a set of explicitly stated assumptions that are too complex to explore by other methods. RIFOD is the first process-based riparian forest dynamics model for Central Europe and can be seen as a step forward into a more integral modelling of the riparian forest dynamics and its processes in view of a decision-aiding tool for large river restoration projects. A future integration of geomorphological processes will allow the application of RIFOD to quasi-natural river conditions.