Integratives Schwebstoffmonitoringkonzept – Innovative Ans?tze auf Basis direkter und indirekter Methoden

This work presents the Austrian monitoring strategy for measuring suspended sediment transport in rivers, the application of which is mandatory at the measurement sites of the Austrian monitoring network provided by the hydrological service and which was published in ??Suspended sediments in rivers??guidelines for the monitoring of suspended sediments.?? In order to determine the temporal and spatial variability of the suspended sediment transport a combination of direct and indirect methods is used. The monitoring methods applied and their interrelation during the data processing via correction factors are described. The monitoring concept was implemented at the Hainburg Stra?enbrücke/Donau measurement site, where a comparison involving different conversion factors was performed. The results of annual and monthly load calculations are presented for the years 2008 and 2009     

Indikatorenbasierte Evaluierung von Fischhabitaten in alpinen Fließgewässern

The EU Water Framework Directive commits member states to achieve good ecological status in all waterbodies. Artificial or heavily modified waterbodies must reach at least its good ecological potential. In view of these requirements, simple and feasible methods are required in order to evaluate habitat suitability for relevant target species in larger river reaches. Well-developed models for determining the relationship between stream flows and habitat for target species mainly based on micro- and meso-scale already exist. However, the application of such models is complex and time-consuming and consequently limited to relatively short river segments. The objective of this study is to develop a simplified applicable assessment model to evaluate habitat conditions for selected target fish. This model uses hydro-morphological indicators for the habitat assessment and relies on correlative relations between habitat suitability and hydro-morphological features of river stretches (average Froude-number, relative flow width, mean bed slope, relative water depth and flow velocity). The indicators were determined as reach-related averages, derived from 2D model simulations (hydraulic and habitat-specific). Particular emphasis was laid on using a wide range of river stretches with different hydro-morphological characteristics (hydrology, bed substratum, bed structures, degree of braiding, sinuosity of the river course, mean bed width and bed slope). As a result, a set of model equations enables the evaluation of fish habitat conditions in river stretches as a function of flow and morphology. The habitat suitability assessment focuses on four preselected target species: brown trout, European grayling and for low slope rivers common nase and barbel.     

Schutz ökologisch sensibler Fließgewässer: Konzepte und Fallbeispiele

European rivers are subject to heavy demand. In this regard, hydromorphological alterations in connection with energy production or flood protection measures are among the most serious issues. Today only very few natural or near-natural river reaches remain, and in Austria only 15% of the rivers are classified as being in “very good” and a further 22% percent as being in “good” ecological condition. In keeping with the objectives of the EU Water Framework Directive, the National River Basin Management Plan defines measures intended to achieve a good ecological status and/or avoid the further deterioration of Austria’s waterbodies.     

Ma?nahmen für einen modernen Flussbau betreffend Sohlstabilisierung und Flussrückbau – Granulometrische Sohlverbesserung, Buhnenoptimierung, Uferrückbau und Gew?sservernetzung

River engineering tasks have changed over time, starting originally from river training for flood protection, navigation, hydropower and agriculture. As a result, significant changes in sediment regimes and morphodynamics occurred, leading to riverbed degradation and related ecological deficits. Consequently, modern river engineering increasingly focuses on riverbed stabilization and restoration measures. Riverbed stabilization measures can be grouped into improvement of the sediment regime, increasing bed resistance to erosion, reducing energy slope and minimizing bed shear stress. Examples such as Granulometric Bed Improvement and increasing bed resistance to erosion explain the principle and effect of the measures. New groin forms and configurations demonstrate the potential integration of goals for navigation and ecology. The examples of riverbank restoration and sidearm reconnection primarily contribute to improving the ecological status, but also to riverbed stabilization and integrated flood risk management.     

Optimierung der Habitatmodellierung an gro?en Flie?gew?ssern unter Berücksichtigung von flussmorphologischen Prozessen auf unterschiedlichen Skalen

In light of the various anthropogenic pressures on our river systems (flood protection, navigation, recreational fisheries) and current legal requirements (European Water Framework Directive), the need for integrative evaluation tools has become increasingly apparent. The so-called habitat modeling approach addresses these integrative efforts to quantify the changing environment for target species (fish, macro-invertebrates), taking into account hydrological and/or morphological changes. Over the course of extensive monitoring on the Danube east of Vienna this specific evaluation tool has been adapted and improved to allow the assessment of river engineering measures in future, especially before their implementation and to determine their potential impacts on the ecological conditions.     

ÖKOHYDRAULIK – Integrative Methoden in Wissenschaft und Praxis im Spannungsfeld der europäischen Richtlinien (Hochwasser-, Wasserrahmen- und Erneuerbare Energie)

The requirements and objectives of those European guidelines that are most relevant for Austrian water management reflect at times disparate perspectives with regard to the current and future use of our waters. In some cases the objectives are in fact diametrically opposed (Renewables Directive and Water Framework Directive), while in others there is the potential for synergies, for example the call for providing more space for rivers (Floods Directive and Water Framework Directive). These potentials for conflict and desirable synergies underline the need to adopt increasingly interdisciplinary approaches, and to translate those approaches into concrete projects. With the help of ecohydraulics, an interdisciplinary field combining hydraulics, river morphology and aquatic biology (as well as vegetation), it is possible to address precisely this need for an integrative perspective, both in fundamental research and in water management practice. With regard to its implementation in river engineering projects, especially habitat modeling approaches concerning different spatial scales allow to assess the varying habitat needs of specific indicator species (macrozoobenthos and fish) in a quantitative and objective way. These methods for quantifying potential habitat changes, e.g. as a water diversion, offer an essential foundation for responding to current and future water management issues.