Small River Catchment Research Articles

Conceptual approach for a holistic low‐flow risk analysis

AbstractLow‐flow events, characterized by a significant water deficiency in river systems, have profound impacts on various water users and river ecology. Recent low‐flow events in Europe have had severe economic and ecological consequences such as disruptions to hydropower production, irrigation bans, constraints on navigation and complete river drying. These events highlight the urgent need for effective low‐flow risk management and demand a holistic risk analysis as a basis. The existing approaches to low‐flow analysis often focus on hydrological aspects, utilizing indices such as the Standardized Runoff Index (SRI) or Low‐flow Index. However, these indices lack information regarding consequences and impacts. Other approaches consider parts of a risk approach but often focus on special aspects, such as the economy; in general, no holistic assessment is made. This study introduces a conceptual approach to a holistic low‐flow risk analysis. The approach provides a continuous long‐term simulation to capture the special long‐term behaviour of low‐flow events and therefore avoids the complex definition of scenarios. In this conceptual approach, the low‐flow risk is analysed using a combination of various analyses that cover all aspects from occurrence to consequences. Meteorological analysis is used to generate synthetic long‐term weather data time series, which are transformed into runoff time series in hydrological analysis. Based on these results, hydrodynamic analysis quantifies the water levels, water temperatures, and flow velocities along the river. The consequences are analysed in terms of socio‐economic and ecological consequences. The results represent a long‐term series of damage values. Finally, the damage values are summed in the risk analysis and divided by the number of years considered in the analysis. For testing and demonstration purposes, the presented conceptual risk approach is partly applied to a proof‐of‐concept at the Selke catchment, a small river catchment in Germany. Finally, the results are presented, evaluated, and discussed.

SPATIAL ESTIMATION OF SOIL EROSION USING GEOSPATIAL TECHNIQUE – A CASE STUDY OF JANJEVA RIVER CATCHMENT (KOSOVO)

The aim of the study is to analyse the spatial estimation of soil erosion in a small size river catchment of Janjeva (Kosovo). Soil erosion is becoming a serious threat and its spatial estimation is crucial for soil resource protection and management. The Revised Universal Soil Loss Equation (RUSLE) methodology integrated with GIS techniques was applied to estimate the annual erosion rate. Different datasets including open-source data were used to find main components of soil erosion. The results show different soil erosion classes depending on lithological settings, landforms, climate conditions, soil properties, land cover and soil conservation practices. By calculating RUSLE parameters for Janjeva River catchment (84 km²), we found out that mean annual erosion rate is 1 t·ha-¹·yr-¹. Erosion rate class <5 t·ha-¹·yr-¹ dominates the catchment’s area with 92.5%, while other classes have 7.5% of catchments total area. Highest rates of soil erosion are found in volcanic rocks, steep slopes and soils without conservation practices. Soils located in western part of the catchment with adequate conservation practice have minimum erosion rate.

Hydrological models and datasets to support flood flow estimation at river-bridge intersections

A working group on the "Hydraulic Compatibility of Bridges" (sites.google.com/view/gii-ponti) has been recently established in the hydraulic engineering academic community aiming at reviewing methodologies, studying good practices, and suggesting guidelines for assessing the bridge hydraulic compatibility. In this initiative, a subgroup is focusing on the hydrological aspects as in Italy there are not standard procedures to estimate design flood values requested by the Italian technical standards of constructions (NTC 2018) over the whole country as, for example, in the UK where the Flood Estimation Handbook provides standard data and methods. Some models are available at the regional scale but are often based on not up-to-date data; moreover, while in large rivers flood discharge values, defined according to the European Flood Directive have been computed and mapped, in small river catchments they are not available.In this context, the unit of Politecnico di Torino working on hydrology is going to release some country-wide hydrological datasets, including all the available official information on discharge and rainfall extremes updated to recent years, that can be used as a common reference for bridge analyses. These include high-resolution maps of extreme precipitation statistics, a database of flood flow extremes recorded at more than 600 river sections, and a catalogue of river catchments characteristics (morphology, climate, land use, etc).Nation-wide datasets can support the application of standardized hydrological analyses, needed for flood hazard assessment, especially in small basins. Operational products will be made available within the PNRR RETURN project in order to be easily available and referable for any hydrological analysis in Italy.

Investigating the influences of climate change on drought in a small data-scarce river catchment

Abstract This study focuses on the influences of climate change on drought characteristics in the small, data-scarce Ndembera River catchment in Tanzania, using the Climatic Research Unit (CRU) datasets and six regional climate models (RCMs) of the CORDEX-Africa framework. The RCM simulations were validated against the CRU data, and their optimistic (RCP 2.6) and worst-case (RCP 8.5) scenarios were used in estimating ensemble simulations using the random forest regression. The ensemble simulations were used to compute standardized precipitation evapotranspiration indices, which characterized drought for the near-future, mid-future, and far-future. Finally, patterns and trends of changes in temperature and precipitation were compared to those in drought characteristics. The findings revealed substantial uncertainty in RCMs, although their ensembles fairly reproduced the historical climate in the catchment. Under the optimistic scenario, a slight decrease in precipitation and a small increase in maximum temperature are projected. Consequently, drought intensity is projected to rise just slightly but remain moderate throughout this century. These changes are expected to be more pronounced during the mid-future than the far-future. Under the worst-case scenario, the projected changes are expected to be more pronounced, especially during the end of the century. These sorts of insights are vital for enhancing adaptations to climate change in catchments.

Flash-flood hazard using deep learning based on H2O R package and fuzzy-multicriteria decision-making analysis

The present study was done in order to simulate the flash-flood susceptibility across the Suha river basin in Romania using a number of 3 hybrid models and fuzzy-AHP multicriteria decision-making analysis. It should be noted that flash-flood events are triggered by heavy rainfall in small river catchments. To achieve the proposed results, a total of 8 flash-flood predictors (slope angle, plan curvature, hydrological soil groups, land use, convergence index, profile curvature, topographic position index, aspect) along with a sample of 111 torrential phenomena points were used as input datasets in the next four algorithms: Fuzzy-Analytical Hierarchy Process (FAHP), Deep Learning Neural Network -Analytical Hierarchy Process (DLNN-AHP), Multilayer Perceptron - Analytical Hierarchy Process (MLP-AHP) and Naïve Bayes - Analytical Hierarchy Process (NB-AHP). The Analytical Hierarchy Process was used to calculate the coefficients for each class/category of flash-flood predictors. The torrential points sample was split into training (70%) and validating samples (30%). The modelling was done in Excel, SPSS and R software (H2O package), while the result mapping was performed in ArcGIS 10.5 software. The analysis revealed that the high and very high susceptibility degrees are spread over a maximum of 35.01% of the study area. The best performances, demonstrated by an AUC-ROC of 0.984, are associated with the Deep Learning Neural Network – Analytical Hierarchy Process model, followed by Naïve Bayes – Analytical Hierarchy Process model (AUC = 0.976), Multilayer Perceptron - Analytical Hierarchy Process model (AUC = 0.882) and Fuzzy-Analytical Hierarchy Process (AUC = 0.807). These results indicates that Deep Learning Neural Network is a promising machine learning model which can provide outcomes with very high precision. Also, according to the present research results the deep learning neural network, having many hidden layers, is able outperform the multilayer perceptron that contains a single hidden layer. The main novelty of the present research is the application of the three ensemble models (DLNN-AHP, MLP-AHP and NB-AHP) and also the use of H2O package for the first time in literature, to evaluate the flash-flood susceptibility in small river catchments.

Catchment‐scale distribution, abundance, habitat use, and movements of European eel (Anguilla anguilla L.) in a small UK river: Implications for conservation management

Abstract Effective conservation management of the Critically Endangered European eel (Anguilla anguilla) is hindered by incomplete understanding of distribution, abundance, and habitat requirements at the catchment scale. All habitats available to eels within a small, highly regulated river catchment, representative of many used across the species' range, were sampled using several methods (including point abundance sample electric fishing and fyke nets) and supplemented by individual telemetry to investigate movements. Eels were found throughout the catchment (59% of n = 131 sites) from the coastal marshes to the headwaters, although the probability of presence declined with distance from the estuary. The lack of a clear relationship with perceived barriers may illustrate a mismatch with the reality experienced by eels, as telemetry identified connectivity across obstacles between paludal habitat and estuary, and detected escapement of mature silver eels from both lotic and lacustrine habitat. Different size/age classes occurred in different parts of the catchment, partly linked to different habitat associations, with coastal paludal habitat supporting >50% of the catchment population and especially smaller (possibly male dominated) yellow eels. Recently recruited elvers were most abundant in the lower reaches of lotic habitat. The largest (probably female) eels were concentrated in lacustrine sites, especially at the ‘end‐of‐the‐line’ in the headwaters. Experiences here suggest that conservation management for eels in small catchments is best focused on: (i) improving connectivity and assisting migration of elvers across ‘problem’ barriers that cannot be removed or modified, (ii) river restoration and rewilding, especially measures that increase instream woody material to provide refuge habitat and, (iii) enhancement or creation (where necessary) of suitable lacustrine habitat to benefit large females in particular. Such action across numerous small river catchments may ultimately help support the recovery of eel stocks.

Baseflow and Stormflow Zinc Loads in a Small Agricultural River Catchment Influenced by an Industrial Area

A stringent environmental quality standard for zinc (Zn) has been enacted by regulators because of its toxicity to aquatic life. This study’s objective was to evaluate the variability of Zn concentrations and fluxes in the baseflow and stormflow and to estimate the contribution of Zn from point and non-point sources. By using high-resolution temporal sampling, the suspended solids (SS), iron (Fe), and Zn concentrations were measured in a small agricultural river catchment. Fe, as the natural non-point source, and Zn were evaluated using the end member mixing analysis (EMMA) to identify the source apportionment (point and non-point). The results indicate that in the baseflow, Zn mainly originated from point sources and was possibly discharged by manufacturing industries. By contrast, the non-point sources (diffuse sources) were responsible for extremely high SS, Fe, and Zn levels in the stormflow. In addition, Zn discharge during the stormflow was 93 times higher than that during the baseflow. According to the EMMA, approximately 74% of the Zn was from point sources. River management can be improved if Zn point sources are adequately treated. During a storm event, it is also important to control the particulate Zn released into the river.

Detecting pollutant sources and pathways: High-frequency automated online monitoring in a small rural French/German transborder catchment

Great temporal and spatial variability of inputs make comprehensive monitoring in small and middle sized rivers difficult. In this study, relevant inputs in a small river were recorded with suitable online monitoring equipment coupled in mobile water quality monitoring stations, the study area being a transborder catchment with French and German (Saarland federal state) subcatchments. In addition to a pronounced spatial variability necessitating a denser net of measuring points this catchment has also to be assessed in the light of different national regulations. To identify individual pollution sources and weigh their relative importance, relevant parameters were recorded over a representative monitoring period of several months: phosphorus (P) as total phosphorus (TP) and total reactive P phosphorus (TRP), nitrate (NO3–N), ammonium (NH4–N), total organic carbon (TOC), temperature, oxygen (O2), pH, turbidity, and electrical conductivity (EC). The recorded data were subjected to adapted interpretation together with other catchment-related factors. In order to retrieve maximum information from the online data sets the relationships among certain parameter pairs were also analysed for both storm events and low flow periods.Comparison of loads at the different monitoring sites could reliably verify the majority of nutrient inputs originating in the French subcatchment. Additional sampling of output channels from sewage treatment works (STWs) in the Saarland subcatchment revealed that inputs from several decentralised STWs do not result in significant loads, as opposed to inputs from one STW in France. Our holistic approach provides a basis for adopting cost-effective measures to reduce loads in small river catchments as well as cross-border harmonisation of environmental policies.

Chemical weathering and carbon dioxide consumption in a small tropical river catchment, southwestern India

Studies done on small tropical west-flowing river catchments located in the Western Ghats in southwestern India have suggested very intense chemical weathering rates and associated CO2 consumption. Very less studies are reported from these catchments notwithstanding their importance as potential sinks of atmospheric CO2 at the global scale. A total of 156 samples were collected from a small river catchment in the southwestern India, the Payaswini–Chandragiri river Basin, during pre-monsoon, monsoon and post-monsoon seasons in 2016 and 2017, respectively. This river system comprises two small rivers originating at an elevation of 1350 m in the Western Ghats in peninsular India. The catchment area is dominated by biotite sillimanite gneiss. Sodium is the dominant cation, contributing ~ 50% of the total cations, whereas HCO3− contributes ~ 75% of total anions. The average anion concentration in the samples varied in the range HCO3− > Cl− > SO42− > NO3− > F−, whereas major cation concentration varied in the range Na+ > Ca2+ > Mg2+ > K+. The average silicate weathering rate (SWR) was 42 t km−2 y−1 in the year 2016 and 36 t km−2 y−1 in 2017. The average annual carbon dioxide consumption rate (CCR) due to silicate rock weathering was 9.6 × 105 mol km−2y−1 and 8.3 × 105 mol km−2 y−1 for 2016 and 2017, respectively. The CCR in the study area is higher than other large tropical river catchments like Amazon, Congo-Zaire, Orinoco, Parana and Indus because of its unique topography, hot and humid climate and intense rainfall.

Integrated Framework for Detecting the Areas Prone to Flooding Generated by Flash-Floods in Small River Catchments

In the present study, the susceptibility to flash-floods and flooding was studied across the Izvorul Dorului River basin in Romania. In the first phase, three ensemble models were used to determine the susceptibility to flash-floods. These models were generated by a combination of three statistical bivariate methods, namely frequency ratio (FR), weights of evidence (WOE), and statistical index (SI), with fuzzy analytical hierarchy process (FAHP). The result obtained from the application of the FAHP-WOE model had the best performance highlighted by an Area Under Curve—Receiver Operating Characteristics Curve (AUC-ROC) value of 0.837 for the training sample and another of 0.79 for the validation sample. Furthermore, the results offered by FAHP-WOE were weighted on the river network level using the flow accumulation method, through which the valleys with a medium, high, and very high torrential susceptibility were identified. Based on these valleys’ locations, the susceptibility to floods was estimated. Thus, in the first stage, a buffer zone of 200 m was delimited around the identified valleys along which the floods could occur. Once the buffer zone was established, ten flood conditioning factors were used to determine the flood susceptibility through the analytical hierarchy process model. Approximately 25% of the total delimited area had a high and very high flood susceptibility.

Impact of the City on the Rapid Increase in the Runoff and Transport of Suspended and Dissolved Solids During Rainfall—The Example of the Silnica River (Kielce, Poland)

Urbanisation changes the water cycle and affects the parameters of transported, suspended and dissolved matter, especially in small river catchments. This paper presents the reasons why river runoff and fluvial transport rapidly increase during rainfall-induced summer floods in the stretch of the Silnica River that flows through the centre of Kielce, a city with a population of 200,000. Examples of implemented hydrotechnical solutions that aim to reduce the height of flood waves and eliminate water accumulation are also presented. The 18.05 km long Silnica River drains a catchment area of 49.4 km2. It flows through areas of varied land use, which have determined the location of five hydrometric stations (outlets) at different sub-catchments: Dabrowa(forest), Piaski (suburbia) and Jesionowa (includes a reservoir), as well as Pakosz and Bialogon (largely impervious areas in the city centre). Specific runoff, suspended and dissolved solids concentration and the specific load of these two types of fluvial transport were determined. It was found that the maximum specific runoff in the outlets of urban sub-catchments was significantly higher during floods than those of the sub-catchments upstream of the city centre; the suspended solids concentration was several times higher, and the suspended solids load was approximately 200 times higher. Recognition of the basic parameters of rainfall-induced flood waves, as well as the dynamics and size of fluvial transport at the hydrometric stations, especially at the outlets of sub-catchments with a large proportion of impervious area (approximately 30%), has become the basis for the development and implementation of modernisation projects and the construction of hydrotechnical facilities and devices in the river channel in the centre of Kielce.

Environmental impact of quarrying of building stones and laterite blocks: a comparative study of two river basins in Southern Western Ghats, India

Mining and quarrying for minor minerals impart significant economic, environmental and social impacts in and around the affected areas. The problem is severe in the small river catchments as the effective area available for assimilating negative impacts of the activity is minimal, compared to large river basins. To address these issues, an investigation has been carried out in two river basins of southern Western Ghats (India)—the Netravati–Gurpur and Periyar–Chalakudy river basins. Both these basins host two important port cities of south India—Kochi and Mangalore. The study reveals that about 6.75 × 106 ty−1 of hard rocks are being extracted in the Netravati–Gurpur basin through 64 quarries. At the same time, the total number of quarries and extracted amounts in the Periyar–Chalakudy river basin are 525 and 10.47 × 106 ty−1, respectively. Many hillocks in the region are turned to a cluster of ugly scars, degrading the ecology and aesthetics of the area. Lowering of water table, modification or disappearance of natural drainages and environmental pollution are some of the other observations noticed in the area. The environmental impacts of laterite quarrying are comparatively less than that of rock quarrying as removal of the hard laterite cap rock enhances water percolation and makes the area more irrigable for agriculture. The study stresses the need for environment-friendly quarrying alternatives with stringent guidelines to improve the overall environmental quality of the area on one hand and to meet the developmental requirements on the other.

Estimating Flood Magnitudes of Ungauged Urban Msimbazi River Catchment in Dar es Salaam, Tanzania

More often daily climate data have been used in hydrological models to estimate flood flows in small data scarce urban and rural catchments where flow peaking and recession are quick within short periods of few hours. This study assesses magnitudes of error of using daily climate data to simulate flood flow hydrographs of a small urban river catchment, Msimbazi River. Spot discharge measurements were available for Apr-May 2014 and MarMay 2015 periods.10-minutes climate records were available at one station, daily temperatures at two stations while daily rainfall records at several stations within the catchment. Visual analysis characterise rainfall events during the 2011, 2014 and 2015 floods, Thiessen-polygon was used for catchment rainfall, Hargreave-Samani model for catchment potential evapotranspiration and flow hydrographs were estimated by calibrated HBV model. Length weighted channel slope was estimated from segment slopes established from available topographical maps and used in estimating time of concentration for the catchment using Kirpich method. Results indicated that simulated flood hydrographs using 10-minutes climate inputs produced higher flood peaks for both December 2011 (peak: 471.6 m3 /s) and April 2014 (peak: 393.5 m3 /s) and expected hydrograph recession behaviour reproducing the Kirpich estimate of time of concentration of 7 hours. Simulated flood peaks using daily climate inputs were 252.3 m3 /s for December 2011 and 205 m3 /s for the April 2014 event being 53% and 52% of those simulated from 10-minutes climate inputs. Despite usefulness of 10-minute climate data, these data are required at more stations within the catchment for reliable simulation of fast receding urban floods and therefore more automatic weather stations are needed in Dar es Salaam.

Microplastic fluxes in a large and a small Mediterranean river catchments: The Têt and the Rhône, Northwestern Mediterranean Sea.

This paper aims at quantifying current riverine fluxes of microplastics (MPs) in two Mediterranean river catchments, a large one and a small one, namely the Rhône and the Têt, which are discharging to the Gulf of Lion in the Northwestern Mediterranean Sea. MP fluxes change markedly through time and space in both river systems. However, no clear relationships between MP concentrations and hydroclimatic conditions have been observed. In the Rhône River a non-linear dilution pattern of MPs in total suspended matter (TSM) during flood conditions could be observed. Although dilution is important, samples during floods exert a strong control on average MP fluxes. Compared to the Rhône River, average MP concentrations in the Têt River were throughout greater and more variable in shape and polymer composition. However, as the study year was exceptionally dry, the average specific MP flux, 76gkm-2y-1, is only slightly larger than the non-flooding value of the Rhône River. We further monitored MP concentrations in shoreline sediments at the mouth of the Têt River to test whether these sediments can represent MP transport in the river. Besides fibers, which probably are easily washed out and transported offshore, MP concentrations and compositions are in agreement with MP loads upstream the river. We also examined the potential role of atmospheric deposition as a source of MP to the Têt River. The average atmospheric MP deposition of 6kgkm-2 y-1 exceeds by far the river average specific MP flux. Moreover, all MPs in atmospheric deposits were fibers, which in terms of mass are of minor importance in the bulk river fluxes. Atmospheric MP deposits may either have been overestimated and/or may be removed from surface waters by efficient removal processes (such as waste water treatment plants).

Changes in the Dynamics and Nature of Sedimentation in Mill Ponds as an Indicator of Environmental Changes in a Selected Lake Catchment (Chełmińskie Lake District, Poland)

The article presents the changes in a hydrographic network resulting from the construction and functioning of nine water mills located in the Struga Rychnowska catchment (Poland). Two ponds (Bierzgieł and Oleszek) have been chosen for a detailed study—both with similar basin origins and morphological settings, but different morphometries, paths of water delivery and discharges from the mill, and water retention times. An attempt was made to restore the course of the deposit sedimentation process in mill pond basins on the basis of historical sources, archived cartographic materials, fieldwork, and laboratory analyses (sedimentology, palynology, and 14C dating). The studies allowed determining the scope of anthropogenic impact on the environment on the example of small river catchment, both when the ponds were in use, and afterwards. Decommissioning of water mills induced a number of serious changes in water resources. The most important of them include: the loss of water retention capacity in the Struga Rychnowska catchment, and decreased ground water level in immediate vicinity of former water reservoirs. Currently, a renewed interest in the old locations of water mills is present, in order to restore retention, and use them for the purposes of modern small hydropower plants (SHP).

Behaviour of Li isotopes during regolith formation on granite (Massif Central, France): Controls on the dissolved load in water, saprolite, soil and sediment

Lithium (Li) contents and isotopes were studied in all environments of a small river catchment draining granite in the Margeride mountains of the French Massif Central. This covered surface waters, primary and accessory minerals of the granites, the whole rock, and soil and sediment samples developed in the catchment, completed with regional data for mineral waters and rainwater. The integrated investigation aimed at evaluating the potential of Li isotopes as effective tracers of water/rock interaction processes within a granitic environment. The δ7Li values and Li concentrations were measured on sediment- and soil samples, following standard acid-dissolution procedures and chemical purification of Li using the cationic exchange resin protocol in a clean lab. Lithium-isotope compositions were measured with a Neptune MC-ICP-MS and Li concentrations by ICP-MS. The samples represented different stages of granite weathering, including fresh granite, weathered-rock, surface saprolite, and sediments in riverbanks and fields bordering the streams. The extent of Li mobility during granite weathering was first evaluated through determining the percentage change relative to Ti, with a range from −31 to −66% in the collected samples. The weathered-rock was depleted by −47% for Li with negative δ7Li values ranging from −1.9 to −3.4‰. Soil to riverbank sediment samples were characterized by less negative δ7Li values, indicating that Li is enriched in soil with fractionation of Li isotopes and changes of the mineral abundance in the samples. To complement this first view, we i) Modelled the theoretical Li isotope signature of water interacting with granite, using a weathering model based on dissolution; ii) Applied an atmospheric-input correction to surface waters; iii) Applied a Raleigh equation for modelling the Li isotope fractionation when compared with corrected surface water and mineral water; and iv) Compared Li isotopes with Sr-isotope data in a larger weathering framework.

The supply of total nitrogen and total phosphorus from small urban catchments into the Gulf of Gdańsk

The main goal of work was to quantify the nitrogen and phosphorus loads transported by small streams to the Gulf of Gdańsk. The research aims to determine wastewater release volumes over time, instead of focusing only on spatial distributions. Another aim is to identify the main determinants potentially affecting water quality in rivers flowing across the city of Sopot. The study area consists of six small river catchments located in the city of Sopot, each with an open flow channel, which lies along the bay. Studies were conducted 12 times per year in the period from March 2014 to February 2015. Laboratory analyses were performed to determine the concentration of both total nitrogen and total phosphorus. In order to calculate pollutant loads, discharge was also measured in each of studied rivers. Conducted research has shown that all analyzed streams were characterized by low total nitrogen and total phosphorus concentrations. The mean annual values ranged from 0.60 to 1.28 mg·dm-3 in case of total nitrogen and from 0.066 to 0.100 mg·dm-3 in case of total phosphorus. In 2012, the total nitrogen load from Poland to the Baltic Sea was 210.768.000 kg N while the total phosphorus load was 15.269.000 kg P, which means that streams analyzed in this paper supplied barely 0.002 % of the biogenic load supplied to the Baltic Sea by Poland as a whole.

EFFECT OF HETEROGENEITY OF RIVERBED ON GROUNDWATER DISCHARGE IN SMALL RIVER BASIN UNDER NATURAL AND STRESSED CONDITIONS

A regional model of catchment of small river (catchment area is about1000 km2) is discussed. Model was developed to evaluate possible influence of hypothetical groundwater intake on river flow. The model was calibrated to measured groundwater heads and river flows. Geophysical and hydrometric survey allowed to characterize a heterogeneity of riverbed along the channel. River flow reduction, calculated on model with riverbed heterogeneity is greater by 25% compared to that calculated without heterogeneity. Thus it is shown that accounting for riverbed heterogeneity is advisable for more reliable prediction of impact of water intakes on environment.

Predicting Flood Hazard Indices in Torrential or Flashy River Basins and Catchments

Flood hazard maps are one of the main components of any flood risk management strategy. It is predicted that the degree of flood risk is going to significantly increase in the future due to climatic and environmental changes, and hence it is increasingly important that state-of-the-art methods are implemented for assessing human stability in floodwaters. Therefore, this paper focuses on proposing more accurate and detailed guidelines for predicting flood hazard indices in small and steep river basins or catchments, prone to the occurrence of flash flooding. The results obtained in this study indicate that for river basins with an average bed gradient greater than 1% (i.e. torrential or flashy river basins or catchments), then the flood hazard indices should be predicted using criteria which are based on the physical interpretation of the processes that affect the human stability in floodwaters, i.e. mechanics based and experimentally calibrated flood hazard assessment methods.

Rainfall-runoff simulation for design flood estimation in small river catchments

This paper presents development and application of the model aimed at simulating peak flood runoff from the small river basin Obnica in Serbia (having an area of 185 km2) with an aim to estimate design floods using different approaches. The model is developed using the HEC-HMS software (The United States Army Corps of Engineers (USACE) Hydrologic Centre?s Hydrologic Modelling System). The model is calibrated against eight events with observed hydrographs and corresponding rainfall, and verified with a separate set of events. Flood hydrographs are simulated with the constant intensity design storms of various durations and with the 24-hour design storm with design hyetograph determined using the alternating block method. All design floods obtained from the simulated hydrograph peaks are compared with the design floods estimated by statistical analysis of annual maximum flows. The results have shown that the temporally distributed 24-hour storms yield the design floods that are the closest to the statistically derived design flows, while the constant intensity storms cannot reproduce the statistically derived design flows.