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JRBM vol 3 Issue 1

The use of elevation data in flood inundation modelling: a comparison of ERS interferometric SAR and combined contour and differential GPS data
By M.D. Wilson and P.M. Atkinson
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Three internationally-available elevation models were assessed for suitability for use in the prediction of flood inundation. The elevation data were selected because they represent data which may be available in data-poor developing countries. These were a contour data set, a remotely sensed dataset (interferometric SAR) and a dataset which may be obtained rapidly through a differential global positioning system (DGPS) survey. The latter dataset was known to have much less uncertainty than the contour dataset and was, therefore, accepted as a benchmark against which to test the other two. Each dataset was used to predict flood inundation for an event in the United Kingdom in 1998 using the two-dimensional model LISFLOOD-FP. The contour dataset was different in spatial character (overly smooth) to the DGPS dataset and resulted in substantial differences in the timing and extent of flood inundation. The interferometric SAR dataset was also different in spatial character (overly rough) to the DGPS dataset although the differences in the timing and extent of flooding were not as great as for the contour dataset. However, results demonstrate potential problems with the use of satellite remotely sensed topographic data in flood hazard assessment over small areas.
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Flood risk reduction by the use of retention areas at the Elbe River
By Saskia Förster, David Kneis, Martin Gocht and Axel Bronstert
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The paper presents research results on flood risk mitigation by the controlled flooding of a retention area on the middle reaches of the Elbe River. The retention area consists of six large polders and the floodplain of a tributary, the Havel, and is located near the Havel's confluence with the Elbe River. The total retention volume of both the polders and the Havel floodplain amounts to approximately 250 millionm3. The controlled flooding of the retention area was simulated by the use of a conceptual model and assessed economically for two flood scenarios. In a cost-benefit analysis, the damage to agriculture, the road network, buildings and fishery caused by the flooding of the polders was compared with the resulting reduction in potential damage in the town of Wittenberge, 30 km downstream. On the basis of a monetary assessment it was concluded that the use of the retention area for flood protection is highly cost-effective in economic terms
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Spatial and temporal drought analysis in the Kansabati river basin, India
By A.K. Mishra, V.R. Desai
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The identification, monitoring and characterization of droughts are of great importance in water resources planning and management. To investigate the spatial and temporal relationships of drought occurrence, the Standardized Precipitation Index (SPI) (calculated from the probability distribution of precipitation using a two-parameter gamma function) was used. The SPIs were applied at the local scale using monthly rainfall data for the period of 1965-2001 from five raingauge stations in the basin. The basin is divided into 25 grid-cells of 13 x 13 km with each grid correspondence to approximately 4% of total area. The inverse distance weighting (IDW) approach is used for the spatial interpolation of rainfall at each grid point. Drought severity is then assessed from the estimated gridded SPI values at multiple time scales. The spatial and temporal characteristics of SPI are used to develop drought severity – area – frequency curves that can assess the severity of the localized drought within the basin. The analysis of SPI suggests that the basin endured severe drought during the 1980's. These frequency curves can be used for planning sustainable water resources projects within the basin.
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Modelling the impact of upstream reservoirs on the fluvial processes in the Aojiang River estuary
By Yongjun Lu, Haolin Li and Xuejun Shao
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The reduction of runoff due to upstream reservoir impoundment can substantially change the fluvial processes in estuaries influenced by strong tidal currents. This paper presents a numerical simulation of such impacts using a coupled 1D–2D model, which takes into account the combined effects of water flow and tidal currents on sediment transport. Simulation results for the Aojiang River estuary on the coast of East China Sea indicate that, in contrast to what usually happens in inland rivers, siltation will dominate the fluvial processes after the reservoir impoundment, and the rise of bed elevation will start upstream from the dam site before it develops rapidly downstream during the first few years of reservoir operation. The deposition will slow down gradually until a balanced state is reached. The re-distribution of sediment deposits in the estuary is found to be non-uniform in both longitudinal and lateral directions. Most sedimentation occurs between two river bends, rather than limited in the bend itself, and a non-uniform distribution is also found over the cross-section of the channel. Reduction of water depth at the port and in the navigation channel will be caused by sediment deposition there, which may affect the navigation conditions.
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Robustness of pollutant loading estimators for sample size reduction in a suburban watershed
By Theodore A. Endreny, J.M. Hassett and S.E. Wolosoff
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Nine estimators of pollutant loading were tested for robustness to sample size reduction in a small suburban watershed of the New York City, USA drinking supply area. Discharge data were recorded from August 2001 to September 2002, which overlapped with collection of 30 baseflow and 35 storm samples for ten constituents (Ca, Cl, DOC, Mg, Na, NH4, NO3, SO4, TN, and TP). Loading estimators were: simple average, period average, linear interpolation average, discharge frequency, Beale Ratio, simple regression, quasi-maximum likelihood (QMLE) regression, smear regression, and maximum variance unbiased estimator (MVUE) regression methods. Sample size reduction explored uniform random removal without replacement down to 10% of the original sample as well as preferential random and non-random reduction of baseflow and storm flow. At 10% random sample reduction, the median departure for estimator loads was 2% from the full-sample prediction, while at 90% of the original sample the median departure was at 35%. Preferential reduction was most robust when storm events were removed, and baseflow retained. In this scenario, median estimator departure remained at 10% given a 75% reduction of storm event samples. Regression estimator methods were generally best when storm event data were not fully removed, and averaging, interpolation, and frequency based estimator methods were best when only baseflow data were retained.
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JRBM vol 3 Issue 2

Dynamic SlowDown: a flood mitigation strategy complying with the integrated management concept – implementation in a small mountainous catchment
By Poulard Christine, Szcz¸esny Jerzy, Witkowska Hanna and Radzicki Krzysztof
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The “Dynamic SlowDown” concept (noted hereafter “DSD”) promotes flood mitigation by slowing down, using transverse obstacles or temporary storage works distributed throughout the catchment. In accordance with Sustainable Development, it aims at reducing the use of the flood defence structures that damage riverine ecosystems. DSD hydraulic projects must be planned at catchment scale and must take all the problems into account, including ecological issues. Cemagref and Cracow Institute ofWater Engineering carried out a DSD feasibility study in a small mountainous catchment in Poland, the Isepnica catchment. To deal with flood and erosion problems, they proposed small storage works on hillslopes and a dry reservoir. To assess their impact on design floods, they developed two simple distributed hydrologic models, and linked them with a hydraulic model built for the main torrent. They concluded that the proposed strategy was efficient. In a further stage, it is envisaged to build and monitor pilot structures, in order to check their behaviour, better calibrate the models, and issue maintenance requirements.
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Historical analyses: a foundation for developing and evaluating river-type specific restoration programs
By Severin Hohensinner, Mathias Jungwirth, Susanne Muhar and Helmut Habersack
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The 350-km-long Austrian Danube river section has been changed dramatically by channelisation in the 19th century and by hydropower plant construction since the 1950s. These have drastically reduced the hydrological connectivity and flood retention capacity of the Danube river landscape. Restoration measures currently under discussion for the Machland floodplain (river-km 2094–2084) aim to re-establish lateral connectivity in floodplain areas that are hydrologically separated from the main channel. This would also help increase the flood retention capacity. In this discussion process, the analysis of historical records provides useful baseline data for estimating natural reference conditions prior to channelisation and improves the evaluation of the effectiveness of selected restoration measures. Here, surveys from 1812 were used to generate a digital terrain model of the former undisturbed river landscape
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Flood risk management in Europe – the development of a common EU policy
By Dipl. Ing. Thomas Dworak and Benjamin Görlach
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Flooding is a natural phenomenon that only becomes a catastrophic event when human lives or property are affected. During the last two decades, flooding events have become noticeably more frequent in Europe and elsewhere. In the wake of the floods of 2002, the Environment Council addressed the issue of precautionary and sustainable flood protection. A European initiative on flooding was started and is continuing to develop. This paper tracks and analyses the EU’s approach by looking at existing legislation and strategies for extending current policy. It outlines the strengths and weaknesses of the initiative and discusses future options.
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A framework for integrating flood defence and biodiversity in washlands in England
By J. Morris, T.M. Hess, D.J.G. Gowing, P.B. Leeds-Harrison, N. Bannister, R.M.N. Vivash and M. Wade
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Concerns about increased flood risk and loss of biodiversity in lowland areas, coupled with changing priorities in the countryside have drawn attention to the potential contribution that managed washlands can make to improved flood management, habitats and wildlife. Following a review of research literature, a survey of flood managers and conservation officers, and an evaluation of selected case sites in England, a framework to help integrate potential flood management and biodiversity opportunities was constructed. This framework consists of three components, namely: a Hydraulic classification which categorises washlands according to degree of hydraulic control; a Habitat classification which captures attributes of washland hydrology that define the type of existing or potential habitats; and, a Menu of Interventions to “engineer” or manage particular flooding and soil wetness regimes and thereby better exploit habitat potential. Washlands were also categorised by main type of benefit whether this is flood management, conservation, or in the case of integratedwashland, a balance of the two. The advantages of alternative administrative and funding arrangements for washlands, whether land acquisition or annual payment to existing land owners, were also explored. It was concluded that the classification of washland flooding and water level regimes can help to define habitat potential. It can also help to guide hydraulic engineering and management actions that can be taken to realise this potential. Although there is potential synergy between flooding and biodiversity under some flood regimes, biodiversity benefits mainly depend on the management of water regimes following flood events. There is a clear need to “join up” hitherto fragmented policy and funding mechanisms in order to exploit the potential for washlands to simultaneously deliver flood management and biodiversity benefits.
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Hydrological and hydraulics modelling to assess mitigation effectiveness of floodplain reconnection in the context of a mountain river
By Nicolas Kreis, Thierry Leviandier and Patrick Arnaud
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Engineering projects combining protection against floods and reconnection of diked areas to the natural flooding regime are very complex and difficult to design at large scale. By using hydrological and hydraulics modelling, engineer and scientists should be able to assess the effectiveness of strategies based on detention in natural or restored floodplains. Flood modelling is based on fine topographic data set on the whole floodplain. Digital Elevation Models with very good altimetric accuracy are now available thanks to airborne laser surveys. Two points must be carefully dealt with in the modelling: unsteady flow simulations must be performed in order to take into account the dynamic storage on floodplain, the hydrographs used as input must be designed in order to yield peak flows of given frequency.We used a stochastic model for hourly rainfall, coupled with a conceptual rainfall-runoff model, to compute many hydrographs for different catchments scales.We built hydrographs which have the same peak flow frequency anywhere along the river. By comparing different restoration scenarios, we can assess the hydrological effectiveness of re-entering riverwaters onto floodplains. For mountain rivers, floodplain reconnection can be advocated to preserve water quality and floodplain biodiversity, but is not a good solution to improve flood mitigation.
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Natural flood reduction strategies – a challenge
By Zbigniew W. Kundzewicz and Lucas Menzel
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Flood hazard and vulnerability to floods tend to increase in many areas, due to changes in socio-economic, and physical – especially climatic – systems. Therefore, increasing attention is being paid to upgrading flood protection systems. As in many vulnerable areas sufficient flood protection cannot be reached with the help of structural means only, further flood damage reduction via non-structural measures is advisable. The most essential principles in natural flood reduction strategies are illustrated by the slogans “keep water where it falls” and “give rivers their floodplains back”, both being widely discussed in Germany, especially after the destructive flooding of August 2002. Examples of implementation of natural flood reduction strategies are presented.
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Managing riverine environments in the context of new water policy in Europe
By Edward Maltby and Martin S.A. Blackwell
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Natural riverine environments are dynamic, and often highly productive, biologically diverse ecosystems. Throughout history human communities have endeavoured to harness the benefits they can provide, but their development largely has ignored the multi-functional nature of these benefits. This has been the result, in part at least, of a segmented and sectoral view of landscape elements which in reality work as an integrated system. The impact has been so great, especially during the last 200 years, that today almost all the large rivers in Europe are to some degree regulated. The uncoupling of rivers from their genetic functional landscape has been enabled and encouraged by inappropriate and non-integrated policy mechanisms such as the Common Agricultural Policy. However, a new management and policy framework is developing out of two parallel initiatives which can become linked to form a powerful engine for change. These are the Water Framework Directive, originating out of Brussels, and the Ecosystem Approach, originating from the Convention on Biological Diversity. A key task for the scientific community now is to help develop the rationale, tools and approach which will support these initiatives and enable innovative policies and decision-makers re-establish the functional linkages which underpin the sustainable use of river catchments.
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JRBM vol 3 Issue 3

Sustainable management of rivers in Malaysia: Involving all stakeholders
By Chan Ngai Weng
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All over the world, including Malaysia, management of rivers is a central issue in this 21st Century. While government has always been traditionally entrusted with the responsibility of managing rivers, increasingly, the public, NGOs (Non-Governmental Organisations), industrialists, farmers, and other stakeholders are playing a greater role. Sustainable management of rivers involves cooperation between countries and states sharing the same river basin, and cooperation between government and all stakeholders. Internationally, countries need to negotiate and use rivers as the basis for peace rather than conflict. In Malaysia, the Federal Government can initiate policies and remain in charge of governance of rivers, in consultation and cooperation with state governments. However, government must relinquish some of its responsibility on river management to all other stakeholders, viz. industrialists, entrepreneurs, farmers, communities/squatters, NGOs, educational institutions, fishermen, conservationists, tourists, the general public, etc. All stakeholders need to start taking proactive actions, even sacrifices, to manage, protect, conserve and restore our rivers so that their resources can be sustained for future use. This is where people from all levels ranging from politicians, policy makers, private companies, NGOs to individuals can play crucial roles. River management and related river issues need to involve NGOs and the people as these issues happen at the local level. Decision-making regarding solutions should be carried out at the lowest appropriate level, ideally involving all stakeholders ranging from government to the private sector, NGOs, the local community and schools. People should be the focus both in decision making as well as active “workers” involved with restoration work. The motto of “Malaysia Boleh” (Malaysia Can) involves all Malaysians. This paper discusses how all stakeholders can contribute by working together in smart-partnerships with government towards effective and sustainable management of rivers in Malaysia.
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An innovative flood forecasting system for the Demer basin: A case study
By Emma Tate and Kris Cauwenberghs
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This paper describes the development and operation of the new flood forecasting system for the Demer basin in Belgium, which has suffered severe flooding problems for many years. The system takes telemetry data from a large number of hydrological, meteorological, and hydraulic observation sites across the basin, along with radar rainfall forecasts. These data are fed through a network of complex hydrological and hydrodynamic models. Scheduled runs of the system take place at frequencies determined by the level of alert; runs are performed on a cluster of server computers, then results are available on client computers in the control room and via remote access. This gives operational basin managers fast, accurate, real-time flood forecasting and flood mapping based on high-resolution digital ground model information, enabling identification of those streets and areas affected by flooding. The basin managers have several options for diverting flood waters in order to avoid or mitigate the effects of flood events in key areas. The forecast results underpin a decision-support system, giving basin managers the information they need to make informed judgements for disseminating flood warnings and altering their management of the river controls
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Environmental modelling in river basin management
By Roger Falconer, Binliang Lin and Richard Harpin
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Details are given of the growing world-wide public concern relating to hydroenvironmental issues for river basin management and examples are cited of some of the flooding and water quality and contaminant problems now being considered by river engineers and managers on a regular basis. The limitations and restrictions of both physical and computer hydraulic models are discussed and concern expressed with regard to the increasing use of computer models being made by non-specialist engineers and scientists – often with little understanding of the complex physical and computational processes involved – to assist in the planning and management of river basin systems. General details are given of the computational or numerical models used for flow, water quality, sediment transport and toxic contaminant concentration predictions in river and estuarine basins and three example studies are described. In these three studies various hydroenvironmental aspects are considered, including: the impact of dynamic decay rates on receiving water quality, refined sediment transport modelling for contaminant transport, flooding and water quality interactions and the use of decision support tools for river basin planning.
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What will it take to bring our rivers back to life?
By Ahmad Fuad B. Embi
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With rapid urbanisation in Peninsular Malaysia, almost all rivers passing through populated areas are suffering from water quality degradation. The subject has received much coverage locally the last ten years. This time the primary sources contributing to this pollution are discussed together with necessary containment measures, many of which are in the early stages of implementation. One of the biggest pollutants is sediment from housing development. This can be controlled through the proposed Erosion and Sediment Control Plan (ESCP), required from all such developers before they begin earthworks. Food, oil and grease waste, solid waste from squatter areas, sewage and other major pollutants are also being tackled although progress is slow.
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Stream restoration and environmental river mechanics
By Pierre Julien, Gigi Richard and Jason Albert
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The impact of construction of dams and reservoirs on alluvial rivers extends both upstream and downstream of the dam. Downstream of dams, both the water and sediment supplies can be altered leading to adjustments in the river channel geometry and ensuing changes in riparian and aquatic habitats. The wealth of pre and post-regulation data on the Middle Rio Grande, New Mexico, provides an excellent case study of river regulation, channel adjustments, and restoration efforts. Cochiti Dam was constructed on the main stem of the Rio Grande in 1973 for flood control and sediment retention. Prior to dam construction, the Rio Grande was a wide, sandy braided river. Following dam construction, the channel bed degraded and coarsened to gravel size, and the planform shifted to a more meandering pattern. Ecological implications of the geomorphic changes include detachment of the river from the floodplain, reduced recruitment of riparian cottonwoods, encroachment of non-native saltcedar and Russian olive into the floodplain and degraded aquatic habitat for the Rio Grande silvery minnow. Recent restoration strategies include removal of non-native riparian vegetation, mechanical lowering of floodplain areas, and channel widening.
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Impacts of hydraulics and sediment transport in river training works and flood control schemes (Case study: Shahroud river)
By Sajad Ahmad Hamidi and Firouz Bahadori Khosrowshahy
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Analysis of hydraulics and sediment transport interactions with river training works and flood control projects is one of the challenging aspects of engineering disciplines. In the course of systematic studies for integrated river training, flood control and zoning master plan preparation for Shahroud river located in the northern part of Iran, the hydraulics of flow and sediment transport phenomena were analyzed. In order to obtain accurate and reliable results and considering complexity of the river system latest version of Hec-Ras, Hec-GeoRas and Hec-6 packages were used for computational purposes. A thorough analysis of system response for a range of design floods with return periods from 2 to 1000 years showed that nearly 80 km of the river requires training, both main channel stabilization and flood control works implementation. To fulfill the training targets a combination of structural measures such as sills, revetments, flood walls, levees and vegetation covers were suggested along with watershed management activities and environmental considerations on the basin.
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Storm water treatment using Bio-Ecological Drainage System
By Khairul Rahmah Ayub, Lariyah Mohd Sidek, Anita Ainan, Nor Azazi Zakaria, Aminuddin Ab. Ghani and Rozi Abdullah
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The treatment of stormwater as it flows through a Bio-Ecological Drainage System (BIOECODS) is the result of a complex interaction between the physical, chemical and biological processes that occur within the system.A stormwater quality monitoring programme at BIOECODS is being carried out by grab sampling method for the period of April–November 2003. Samples of stormwater are taken from ten stations along ecological swales and eight stations along ecological pond. The ecological pond (wet pond, detention pond, constructed wetland, wading river and recreational pond) which is placed downstream acting as a facility to control the storm water quantity and storm water treatment device before storm water flows into Kerian River. The ecological pond system is strategically placed at the downstream end of the BIOECODS to optimize and effectively attenuate and treat storm water runoff generated from the USM Engineering Campus development area.
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The importance of sullage (grey-water) treatment in the restoration and conservation of urban streams
By Azni Idris, Wan Nor Wan Azmin, Mohd. Amin Mohd. Soom and Abdullah-Al-Mamun
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Sullage (grey-water) is one of the major point pollution sources, which is discharged from residential and commercial areas into the rivers without any treatment. This study was conducted to determine the pollution characteristics of sullage from a 6.14-hectare residential area where it is discharged into an urban stream without any treatment; and thereafter, to evaluate its probable consequences on the water quality of urban streams. Analyses of the hourly samples revealed that the sullage from residential area was polluted due to high concentration of BOD, COD, Ammoniacal Nitrogen (AN), Orthophosphate (PO4) and TKN, and low concentration of DO. Mean concentrations of the above-mentioned parameters from 72 samples were 51, 123, 5.4, 2.15, 2.15 and 1.62 mg/l, respectively. Further analyses of data revealed that, on average, the sullage was equivalent to Class V water as defined by the water quality index (WQI) in NationalWater Quality Standards (INWQS) of Malaysia. Most of the urban streams drain return water (wastewater) from the settlements and lack adequate baseflow to dilute the wastewaters. As such, if the return waters are not treated then the urban streams shall never be able to achieve the required goals. Domestic sewage and industrial wastewaters are treated to some extent, to achieve the standards stated in Environmental Quality Act, 1979. On the contrary, although quantity and quality of sullage plays important role on stream water quality, it is neither taken care of by any agency nor controlled by any standard. As such, it is important to make necessary technical, institutional and legal arrangement to treat sullage up to certain standard before it find its way into the urban streams.
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Effects of urbanization on runoff water quantity and quality: Experiences from test catchments in Southern Finland
By Nora Metsäranta, Jyrki Kotola and Jyrki Nurminen
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The main theme of this paper is to assess the complexity of rainfall-runoff process in urbanized areas. Effects of paved and impervious surfaces on rainfall-runoff process and storm water quality are described in three different urban study areas. Conclusions on the hydrological and water quality effects of urbanization were drawn from the results of two Finnish research projects and from the measurements carried out at the Helsinki University of Technology since the year 2001.
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JRBM vol 3 Issue 4

Impacts of the TGP project on theYangtze River ecology and management strategies
By Zhao-Yin Wang, Joseph H.W. Lee and Dongsheng Cheng
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TGP project – the Three Gorges Project on the Yangtze River – is the largest hydro-project in China. This paper outlines the environmental and ecological impacts of the project. Cumulative sedimentation in the reservoir will reach an equilibrium in 100 years with a total volume about 16 billion m3. The planned Xiangjiaba and Xiluodu reservoirs, which will be located at 1020 km and 1180 km upstream of the TGP dam, can be used to trap sediment and thus reduce the sedimentation rate of TGP reservoir in the first 90 years. Experimental studies showed that impoundment of TGP reservoir will cause sediment deposition at the apron of the Chongqing harbor and even change the stem flow from the west channel to the east channel. Building spur dykes and groins to regulate the flow can solve the problem. Calculation with 1-D models show that the released water from the dam will scour 2.5 billion tons of sediment from the downstream channels in 40 years, which will result in channel degradation. The flood stage will then be reduced by about 3m at Shashi and 0.75m at Wuhan for a flood of discharge 30,000m3/s. Studies indicate that the reservoir will not necessarily cause earthquakes, but will induce more landslides, which will threaten little the safety of the dam. It is reported that the impoundment of the reservoir so far has not obviously affected the water quality. The reservoir operation will change the hydrologic conditions, which may affect the life cycle and habitats of fishes and reduce the fishery harvest. The regulation of the flow for power generation and flood control may change the fluvial processes and some meandering and braided sections may become unstable, which will undermine the habitats of some endangered species. The longer the time of channel bed stability, the more species of benthic invertebrate may live and propagate on the riverbed. The number of benthic invertebrate will reduce because the erosion and sedimentation will make the channel bed unstable. New resettlement policy has been implemented with overall arrangements for production and living conditions for the emigrants. The farmland to be inundated would be about 23,000 hectares. Experiments in the reservoir area indicate that about 27,000 barren slope-land may be transformed into a terraced citrus orchard and it is able to turn out an output value equal to as much as those by the inundated land.
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Basin influence on natural variability of rivers in semi-arid environments
By Domingo Baeza Sanz, Diego García Del Jalón, Barbara Gutiérrez Teira and Pilar Vizcaíno Martínez
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Scientific evidence indicates that freshwater aquatic ecosystems can be protected or restored by recognising that dynamic flow patterns must be maintained within the natural range of variation to promote their integrity and sustainability. An evaluation of the required conditions for healthy functioning needs to begin with a description of natural streamflow patterns. In order to characterise the flow regimes of a group of rivers located in central Spain, data was taken from 25 gauging stations in a major river basin to establish a hydrological grounding upon which to base biological studies. A number of basin variables were also obtained, and this paper considers the relationships that exist between relevant ecohydrological indices and these basin characteristics. Special importance has been attached to low flow characterisation, since these situations are important determining factors for the development and evolution of biological populations. The results show a significant relationship between one of the low flow indices and basin lithology, evapotranspiration and river basin size. Finally, two models have been found which allow low flow volume values to be estimated from these river basin variables. These models can be used to obtain low flow values in river basins where gauging stations do not exist.
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Assessing the hydrological effects of Landuse changes using distributed hydrological modelling and GIS
By Seifu Gebremeskel, Yong B. Liu, F. de Smedt, Lucien Hoffmann and Laurent Pfister
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A distributed hydrological modelling and GIS approach was applied for the assessment of landuse changes in the Alzette basin, Grand-duchy of Luxembourg. The assessment focused on the potential impact of landuse changes on the hydrological processes. Three scenarios were established and investigated. The first scenario considered a realistic increase of urbanisation, while the other scenarios were hypothetical, i.e. forest was converted to agricultural land or the opposite. Comparison of the results for each scenario showed that although the overall changes in the total evapotranspiration and river discharge remained small, that change observed in the different component of the discharge was important. Urbanisation could increase floods by 26% and deforestation increased peak discharges, but to a lesser extent. The afforestation scenario reduced peak flows by as much as 5.3%. Moreover, the afforestation scenario increased soil moisture and base flow.
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Numerical modeling of algae in the Patuxent Estuary
By Sen Bai and Wu-Seng Lung
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The Patuxent Estuary, a tributary of the Chesapeake Bay, has suffered excessive algal productivity over the last several decades. Although the phosphorus and nitrogen loads from point sources have been dramatically reduced since the 1980s and 1990s with costly management practices, the algal bloom problem has not been improved significantly. A physical-biological model using the CE-QUAL-W2 framework was developed to address the eutrophication processes in the Patuxent Estuary and serve as a linkage between watershed model and aquatic ecosystem and fishery model. The model was calibrated with 1997–1998 data and verified with 1998–1999 data. The impact of land use change in the PatuxentWatershed on algal productivity was examined by running scenarios representing land use changes and subsequent load reduction or load increase. Model results revealed that there is no simple positive or negative correlation between watershed nutrient loads and algae productivity. Under low freshwater inflow conditions, nutrients are the limiting factors, while physical transport plays a more important role than nutrients under high flow conditions. In addition to watershed nutrient loads, internal nutrient release from sediment may become important under low dissolved oxygen conditions.
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Morphological numerical simulation of flood situations in the Danube River
By Bui Minh Duc, Hans Helmut Bernhart and Horst Kleemeier
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A depth-average model using a finite-volume method with boundary-fitted grids has been applied to simulate morphological processes in the Danube River. The numerical model consists of three basic modules: a hydrodynamic module describing the depth-average flow and the water surface elevation, a sediment transport module, and a sediment-balance module providing the sedimentation and erosion rate and the bed level deformation. The secondary flow transport effects are taken into account by adjusting the dimensionless diffusivity coefficient in the depth-average version of the k ?? turbulence model. The numerical model has been developed, tested and validated previously by computing various flow situations in laboratory channels and natural rivers. This paper presents the results of an application of the model to flood situations in one stretch of the Danube River. The predictions are compared with field data measurements. Detailed comparison of the flow field shows generally good agreement. Some problems of model calibration for sediment transport are discussed. Calculations have been carried out to study morphological characteristics under extreme flood conditions in the river stretch.
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Book Review - Tools in fluvial geomorphology (G. MATHIAS KONDOLF and HERVÉ PIÉGAY, John Wiley and Sons Limited, Chichester)
By John Wainwright
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Book Review - Environmental hydraulics of open channel flows (H. CHANSON, Elsevier Butterworth-Heinemann, Oxford)
By Matthew Wilson
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Sediment transport equation assessment for selected rivers in Malaysia
By CHANG CHUN KIAT, AMINUDDIN AB. GHANI, NOR AZAZI ZAKARIA, ZORKEFLEE ABU HASAN and ROZI ABDULLAH
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This paper describes a total of 122 sediment data obtained from May 2000 until October 2002 at Kinta River Catchment in the river sediment collection and analysis project. Data collection including suspended load, bed load, bed material and flow discharge have been carried out at six study sites consisting of four rivers which are situated at Kinta River Catchment, namely Kinta River, Pari River, Raia River and Kampar River. The sediment transport equation assessments have been carried out using Yang, Engelund & Hansen, Ackers & White and Graf equations. The results of Yahaya (1999) and Ariffin (2004) studies for Kerayong River, Kulim River and Langat River catchment (224 sets of data) are also included in this present study.
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