Flood risk management is founded on the regular assessment of damage potential. A significant parameter for assessing damage potential is the number of at-risk objects. However, data sets on exposure are often incomplete and/or lack time-references. Airborne remote sensing data, such as orthophotos, offers a regularly-updated, time-referenced depiction of land use. As such, remote sensing data compensates for incomplete data sources (such as digital cadastral maps). Orthophotos can even be used to analyze the temporal dynamics of flood damage potential, providing that timereferenced information is available for multiple time points. This paper describes a method for integrating orthophotos into flood risk analyses. In Austria, orthophotos are updated every three years, allowing their integration into cyclical flood risk assessments. The results of a case study presented in this paper demonstrate that orthophotos are most useful where other data sources, such as digital cadastral maps, are incomplete. In such situations, orthophotos lead to a significant increase in estimated damage potential. Orthophoto analysis allows damage potentials to be re-assessed at regular intervals, another major advantage over digital cadastral maps. Orthophoto analysis thus supports the evaluation of flood risk management options.
To reveal and evaluate the mechanism of transforming rainfall into runoff in the region, where the subsurface flow plays a dominant role in the runoff formation, a continuous hydrological and climatic data monitoring has been set-up in the experimental catchment Uhlířská (the Jizera Mountains, CR). The soil profile (Dystric Cambisol), formed on the weathered granite bedrock, is shallow and highly heterogeneous. Beside a standard catchment data observation a hillslope transect was instrumented to control the flow dynamics in the soil profile. From three soil horizons, the subsurface outflow is recorded in the subsurface trench. Adjacent to the trench the soil water suction is scanned by triplets of automatic tensiometers. Within the soil profile the unsaturated regime prevails, nevertheless the soil keeps almost saturated. Nearly simultaneous reaction of suction on a rainfall in all soil horizons implies a rapid vertical flow. Local preferential flow paths are conducting infiltrating water at significantly variable rates when saturation is reached. Groundwater table, soil moisture and subsurface runoff measured at the hillslope transect and the total outflow from the catchment, are correlated. The outflow from the catchment is dominantly controlled by soil moisture however the mechanism of its generation is not yet fully understood. and V oblasti s dominantním podpovrchovým odtokem bylo započato s kontinuálním hydrologickým a klimatickým monitoringem s cílem popsat a vyhodnotit transformaci srážky na odtok. Experimentální povodí Uhlířská se nachází v severní části České republiky v Jizerských horách. Půdní profil, klasifikovaný jako dystrická kambizem na zvětralém žulovém podloží, je mělký a velmi heterogenní. Svahový transekt byl vystrojen pro sledování dynamiky podpovrchového odtoku. Ve třech půdních horizontech je monitorován odtok a půdní sací tlak. V půdním profilu převládá nenasycený stav, ačkoliv je půdní vlhkost dlouhodobě blízko nasycení. Rychlé vertikální proudění je indikováno téměř současnou odezvou půdního sacího tlaku na srážku ve všech půdních horizontech. Po dosažení nasycení infiltrující voda protéká preferenčními cestami s výrazně odlišnými lokálními rychlostmi. Závislost hladiny podzemní vody, půdní vlhkosti, podpovrchového odtoku ve svahovém transektu na odtoku z povodí je významná. Odtok vody z povodí, které leží na zvětralém žulovém podloží, je dominantně určován půdní vlhkostí. Přes tato zjištění není mechanismus tvorby odtoku zatím jednoznačně popsatelný.
By an analysis of the Brock’s model tests (Brock, 1969) conditions for forming of roll-waves are determined together with experimental equations of their parameters in relation to the channel inflow wave (Kunštátský, Maleňák, Pejchal, 1967; Kybast, 2002), aeration of flow (Douma, 1943; Haindl, Lískovec, 1973), channel slope and roughness along the whole range of the water flows. Calculations of lower and upper flow roll-waves discharge, depths, velocities, time periods, wave distances and volumes are presented. and Rozborem Brockových modelových zkoušek (Brock, 1969) jsou určeny podmínky tvoření translačních vln a experimentální rovnice jejich parametrů v souvislosti s rázovou vlnou napouštění koryta (Kunštátský, Maleňák, Pejchal, 1967; Kybast, 2002), s provzdušněním proudu (Douma, 1943; Haindl, Lískovec, 1973), sklonem koryta a s jeho drsností v celém rozsahu tohoto proudění vody. Předložen je výpočet dolního proudu a horního proudu s translačními vlnami, jejich průtoků, hloubek a výšek, rychlostí, časových period, vzdáleností a objemů vln.
Soil water availability, nutrient supply and climatic conditions are key factors for plant production. For a sustainable integration of bioenergy plants into agricultural systems, detailed studies on their water uses and growth performances are needed. The new bioenergy plant Igniscum Candy is a cultivar of the Sakhalin Knotweed (Fallopia sachalinensis), which is characterized by a high annual biomass production. For the determination of transpiration-yield relations at the whole plant level we used wicked lysimeters at multiple irrigation levels associated with the soil water availability (25, 35, 70, 100%) and nitrogen fertilization (0, 50, 100, 150 kg N ha-1). Leaf transpiration and net photosynthesis were determined with a portable minicuvette system. The maximum mean transpiration rate was 10.6 mmol m-2 s-1 for well-watered plants, while the mean net photosynthesis was 9.1 µmol m-2 s-1. The cumulative transpiration of the plants during the growing seasons varied between 49 l (drought stressed) and 141 l (well-watered) per plant. The calculated transpiration coefficient for Fallopia over all of the treatments applied was 485.6 l kg-1. The transpiration-yield relation of Igniscum is comparable to rye and barley. Its growth performance making Fallopia a potentially good second generation bioenergy crop.
The use of treated wastewater (TWW) for agricultural irrigation becomes increasingly important in water stressed regions like the Middle East for substituting fresh water (FW) resources. Due to elevated salt concentrations and organic compounds in TWW this practice has potential adverse effects on soil quality, such as the reduction of hydraulic conductivity (HC) and soil aggregate stability (SAS). To assess the impact of TWW irrigation in comparison to FW irrigation on HC, in-situ infiltration measurements using mini disk infiltrometer were deployed in four different long-term experimental orchard test sites in Israel. Topsoil samples (0-10 cm) were collected for analyzing SAS and determination of selected soil chemical and physical characteristics. The mean HC values decreased at all TWW sites by 42.9% up to 50.8% compared to FW sites. The SAS was 11.3% to 32.4% lower at all TWW sites. Soil electrical conductivity (EC) and exchangeable sodium percentage (ESP) were generally higher at TWW sites. These results indicate the use of TWW for irrigation is a viable, but potentially deleterious option, as it influences soil physical and chemical properties.
Climate change impacts on the regional water cycle represent a long-term ''system disturbance'' and belong to the most urgent issues of today’s hydrological research. Stronger research efforts are needed especially at the regional and local scale, where political and technical adaptation measures can be taken to avoid critical developments for the environment and society. Studies in the past indicate considerable regional vul-nerabilities against changes of both temperature and precipitation patterns. The present study describes a methodology, which allows to assess the influences of climate changes in a meso-scale region. Results of a high temporal and spatial resolution mod-elling approach are presented for the State of Brandenburg in Eastern Germany, which suffers from water deficit similar to many Mediterranean regions. The study indicates strong impacts on various water balance components under changed climatic condi-tions in the period 1996-2050 and possible water availability problems in the future. Basis for the impact study are trend analyses in Brandenburg, which indicate a signifi-cant decrease of percolation already in the observation period 1961-1998, especially for areas with a shallow groundwater table. and Dopady zmeny klímy na hydrologický cyklus v regionálnej mierke predstavujú dlhodobé ''narušenia systému'' a patria k najnaliehavejším otázkam súčasného hydrologického výskumu. Výraznejšiu pozornosť výskumu si vyžadujú najmä problémy v regionálnej a lokálnej mierke, kde môžu byť prijaté opatrenia, ktoré umožnia vyhnúť sa krízovému vývoju v životnom prostredí a spoločnosti. Minulé štúdie poukázali na veľkú regionálnu zraniteľnosť voči zmenám teploty a atmosférických zrážok. Tento príspevok opisuje metodológiu odhadu vplyvov zmeny klímy v regióne veľkosti mezomierky. Sú v ňom prezentované výsledky modelovania s vysokým časovým a priestorovým rozlíšením v krajine Brandenbursko vo východnej časti Nemecka. Štúdia poukazuje na významné dopady zmenených klimatických podmienok pre obdobie 1996-2050 na rôzne prvky hydrologickej bilancie a možné problémy so zdrojmi vody v budúcnosti. Základom impaktovej štúdie je trendová analýza, ktorá poukazuje na významný pokles perkolácie už v pozorovanom období 1961-1998, najmä v oblastiach s plytkou hladinou podzemnej vody.
The main aim of this work is to evaluate the development of rainfall-runoff regime in selected river basins of the Šumava Mountains (Bohemian Forest), the Jeseníky Mountains and the Krušné Mountains (Ore Mountains) in the last 50 years. Besides the identification of inhomogeneity in time series of mean discharges, rainfall amounts, temperature and snow cover data, the work deals with an analysis of trends using annual and monthly data. Different methodological tools for identification of changes and trends in hydro-climatic time series have been introduced in this study, especially different methods of statistic testing and an application of Mann-Kendall seasonal test. The results have been compared not only from the point of view of the methods applied here, but as well from the viewpoint of geographical difference of the mentioned areas. and Hlavním cílem předložené studie je zhodnotit vývoj srážko-odtokového režimu ve vybraných povodích v oblasti Šumavy, Jeseníků a Krušných hor za posledních 50 let. Vedle zjišťování nehomogenit v časových řadách průměrných průtokových, srážkových, ale i teplotních a sněhových dat se práce zabývá analýzou trendů na úrovni ročních hodnot a jednotlivých měsíců. V práci jsou představeny různé metodické nástroje ke sledování změn a trendů v hydroklimatologických řadách, zejména různé metody statistického testování a aplikace Mann-Kendallova sezónního testu. Výsledky jsou porovnány nejen z hlediska použitých metod, ale i geografické rozdílnosti sledovaných území.
Field observations showed that in many gravel-bed rivers, rice stems and gravel interact with each other and affect the flow structure. This calls to conduct research in more details in laboratory to better understand impacts of interaction between rice stems and gravel bed rivers on the flow structure. The outcome of such investigations can improve the estimation of drag coefficient in hydrodynamic models. Experiments were carried out in a flume with gravel bed and the vegetated vertical flume walls to investigate turbulence characteristics under favorable pressure gradient flows. Results showed that the stress fraction involves both the sweep and ejection dominance near the vegetated flume walls, showing no negative Reynolds shear stress near water surface. The values of exuberance ratio play a significant role on the magnitude of the Reynolds shear stress which varies with the distance from the vegetation. Quadrant analysis reveals that a major part of the momentum flux is transported during a short period of strong turbulence activity near the bed at the central axis. Augmentation of the hole size makes difference between contributions of sweep and ejection with those of the outward and inward interactions near the bed, however, the hole size doesn’t play any role near the water surface.
Turbulence of flow over mobile bedforms in natural open channels is not yet clearly understood. An attempt is made in this paper to determine the effect of naturally formed mobile bedforms on velocities, turbulent intensities and turbulent stresses. Instantaneous velocities are measured using a two-dimensional particle image velocimetry (PIV) to evaluate the turbulence structure of free surface flow over a fixed (immobile) bed, a weakly mobile bed and a temporally varying mobile bed with different stages of bedform development. This paper documents the vertical distribution of velocity, turbulence intensities, Reynolds shear stress and higher-order moments including skewness and turbulent diffusion factors. Analysis of the velocity distributions shows a substantial decrease of velocity near the bed with increasing bedform mobility due to increased friction. A modified logarithmic law with a reduced von Kármán constant and increased velocity shift is proposed for the case of the mobile bedforms. A significant increase in the Reynolds shear stress is observed in the mobile bedforms experiments accompanied by changes over the entire flow depth compared to an immobile bed. The skewness factor distribution was found to be different in the case of the flow over the mobile bedforms. All higher-order turbulence descriptors are found to be significantly affected by the formation of temporally varying and non-equilibrium mobile bedforms. Quadrant analysis indicates that sweep and outward events are found to be dominant in strongly mobile bedforms and govern the bedform mobility.
Two original electrical methods of dikes monitoring (temperature scalar field and electrical impedance spectrometry) are described in detail. Using these methods, the non-stationary movement of the free water level in the dike can be indicated. The methods also enable to detect the piping in the dike due to the activity of animals. Some results are shown and discussed. and V příspěvku jsou uvedeny dvě neinvazivní metody (metoda měření teplotního skalárního pole a elektrické impedanční spektrometrie), které byly laboratorně ověřeny při monitorování nestacionárního pohybu volné hladiny vody v ochranných hrázích. Tyto metody navržené a ověřené autory příspěvku rovněž umožňují detekovat objemové změny (velikost nádrže při přelití koruny hráze, působení drobných živočichů apod.) konstrukce ochranné hráze. Některé ze získaných výsledků jsou zde uvedeny a diskutovány.