Session B6: Hydraulic Research on Fish Passage Design at Lock & Weir Sites

Abstract: Both European and Belgian legislations aim at restoring and enhancing the ecological strength of the water systems. Besides improvement of water quality and protection through legislation, restoration of free fish migration on the rivers and main waterways. To solve the problem of the disruption of longitudinal habitat connectivity by manmade obstacles such as locks and weirs, fish passages are constructed. In close cooperation with the Institute for Nature and Forest Research (INBO) of the Flemish Government (hydraulic) research on fish passage design at weir-lock sites on Flemish rivers has been done since 1995 at Flanders Hydraulic Research (FHR). The research is done via scale model tests, field measurements and literature study. To determine the effectivity of a fish passage both passability and attractiveness are assessed. The passability requires limitations to the maximum velocity and minimal depth along the fish passage. The attractiveness is defined as the extent to which fish can find the entrance of the fish passage. To obtain maximum attractiveness an attraction flow at the passage entrance is applied. The presentation gives an overview of the FHR research. Regarding the passability current results and research questions relating both nature like fish passages as bypass channels and more technical solutions as V-shaped fish ladders and vertical slot passages are addressed. Also previous research on swimming and leaping capacities that has been done with living fish is presented. In recent years several scale model tests have been done regarding the attractiveness of fish passages downstream of weirs applying a perpendicular attraction flow. Current research focusses on the comparison of perpendicular with parallel attraction flows and on sharp bends in Vshaped fish ladders

Potential implications of sea-level rise for Belgium

The Belgian coastal plain and the Schelde estuary are threatened by sea-level rise. While of great economic importance with a threatened population of some 0.8 million (of a total population of 10 million), assessments of these risks are limited. This article describes the physical characteristics of the coast and undertakes a qualitative interpretation of its vulnerability. Low-lying polders are the most vulnerable to sea-level rise where a major problem is water drainage during rainy periods; their varying vulnerability to sea-level rise and increase in rain intensity is assessed, including the relationship between drainage levels and saltwater seepage. Freshwater lenses developed within the dunes are also vulnerable to sea-level rise, leading to threats to drinking water supplies from saltwater intrusion. Belgian coastal defence structures and their effectiveness are discussed. Historical sea-level rise during the past century, wave and wind data, and the evolution of erosion and accretion along the coast are interpreted. For Antwerpen, a harbour city on the river Schelde, the effects of sea-level rise are far from clear. Included here are historical data on changes in tidal amplitude during the 20th century. Future research needs should focus on the quantitative interpretation of data to understand the effect of sea-level rise on beach erosion, flood risk, and fresh and salt groundwater distribution. Furthermore, a thorough socio-economic study should be undertaken to assess the vulnerability of the Belgian coast and the Schelde estuary

The distribution of interstellar dust in CALIFA edge-on galaxies via oligochromatic radiative transfer fitting

We investigate the amount and spatial distribution of interstellar dust in edge-on spiral galaxies, using detailed radiative transfer modeling of a homogeneous sample of 12 galaxies selected from the CALIFA survey. Our automated fitting routine, FitSKIRT, was first validated against artificial data. This is done by simultaneously reproducing the SDSS $g$-, $r$-, $i$- and $z$-band observations of a toy model in order to combine the information present in the different bands. We show that this combined, oligochromatic fitting, has clear advantages over standard monochromatic fitting especially regarding constraints on the dust properties. We model all galaxies in our sample using a three-component model, consisting of a double exponential disc to describe the stellar and dust discs and using a S\'ersic profile to describe the central bulge. The full model contains 19 free parameters, and we are able to constrain all these parameters to a satisfactory level of accuracy without human intervention or strong boundary conditions. Apart from two galaxies, the entire sample can be accurately reproduced by our model. We find that the dust disc is about 75% more extended but only half as high as the stellar disc. The average face-on optical depth in the V-band is $0.76$ and the spread of $0.60$ within our sample is quite substantial, which indicates that some spiral galaxies are relatively opaque even when seen face-on.Comment: 18 pages, 6 figures, 4 tables, Accepted for publication in MNRA

Assessment of the attraction flow in a fish passage

An attraction flow can be used to increase the effectivity of a fish passage. In 2004 a fish passage with a perpendicular attraction flow was built at Oudenaarde (Belgium) on the Upper Scheldt river. The design of the passage was based on scale model tests. In order to evaluate the hydraulic effectivity of the attraction flow, field measurements and new scale model tests are done. Velocities in the attraction flow and the fish passage entrance are assessed quantitatively and data of the scale model tests (1/15) are compared with the field measurements. The measured reach of the attraction flow seems to differ from results of the original scale model tests due to design modifications of the fish passage entrance. Results of the new scale model tests compare well with the data from the field measurements. Based on the results, a re-examination of the basic design rules for the attraction flow and fish pass entrances seems imperativ

LINKING URBAN (STREET CANYON) MODELS WITH REGIONAL AIR QUALITY MODELS THROUGH URBAN BOUNDARY CONDITIONS

This contribution addresses the question of how detailed information from the urban canopy can be assimilated into regional models. This detailed information concerns, among others, road transport emissions, specific exchange and turbulence patterns in the built up canopy, and effects of roads and roughness elements on wind direction and wind speed. This information is typically obtained from detailed street canyon models in combination with traffic emission models. In order to integrate the dynamics of the urban canopy into regional air quality models, we propose the formulation of urban boundary conditions. The formulation has been tested and compared with measurements for benzene and NOx in the city of Antwerp, Belgium

Bulletin agrométéorologique - Situation au 30 septembre 2007

Les conditions météorologiques depuis le 20 août dernier, date du dernier bulletin, ont été très proches des conditions normales. Mis à part quelques orages locaux, aucun phénomène météorologique particulier n’est à signaler. Les rendements satisfaisants à bons annoncés dans le dernier bulletin pour les cultures de maïs, betterave et pomme de terre sont confirmés

H-ATLAS/GAMA and HeViCS - dusty early-type galaxies in different environments

NKA acknowledges the support of the Science and Technology Facilities Council. LD, RJI and SJM acknowledge support from the European Research Council Advanced Grant COSMICISM. IDL gratefully acknowledges the support of the Flemish Fund for Scientific Research (FWO-Vlaanderen). KR acknowledges support from the European Research Council Starting Grant SEDmorph (P.I. V. Wild). Date of acceptance: 22/05/2015The Herschel Space Observatory has had a tremendous impact on the study of extragalactic dust. Specifically, early-type galaxies (ETG) have been the focus of several studies. In this paper, we combine results from two Herschel studies -a Virgo cluster study Herschel Virgo Cluster Survey (HeViCS) and a broader, low-redshift Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS)/Galaxy and Mass Assembly (GAMA) study -and contrast the dust and associated properties for similar mass galaxies. This comparison is motivated by differences in results exhibited between multiple Herschel studies of ETG. A comparison between consistent modified blackbody derived dust mass is carried out, revealing strong differences between the two samples in both dust mass and dust-to-stellar mass ratio. In particular, the HeViCS sample lacks massive ETG with as high a specific dust content as found in H-ATLAS. This is most likely connected with the difference in environment for the two samples. We calculate nearest neighbour environment densities in a consistent way, showing that H-ATLAS ETG occupy sparser regions of the local Universe, whereas HeViCS ETG occupy dense regions. This is also true for ETG that are not Herschel-detected but are in the Virgo and GAMA parent samples. Spectral energy distributions are fit to the panchromatic data. From these, we find that in H-ATLAS the specific star formation rate anticorrelates with stellar mass and reaches values as high as in our Galaxy. On the other hand HeViCS ETG appear to have little star formation. Based on the trends found here, H-ATLAS ETG are thought to have more extended star formation histories and a younger stellar population than HeViCS ETG.Publisher PDFPeer reviewe

Toekomstverkenning MIRA 2009 Wetenschappelijk rapport verzuring

In dit wetenschappelijk rapport worden de jaargemiddelde deposities, sectorale bijdragen en de overschrijding van kritische lasten voor verzuring bepaald in Vlaanderen, en dit voor twee MIRA-scenario’s, met name REF- scenario en EUR-scenario, voor de potentieel verzurende stoffen (NHx, NOy en SOx) voor de periode 2010 t.e.m. 2030. Het jaar 2006 werd beschouwd als referentiejaar. Er wordt ook bepaald wanneer herstel van bodemverzuring kan verwacht worden voor Vlaamse bosbodems