Sewer model development under minimum data requirements

Planning, design and operation of urban drainage systems is often based on hydraulic sewer modelling. Sewer models are also increasingly used to quantify pollution loads discharged to aquatic ecosystems (e.g. via combined sewer overflows), which ultimately allows an estimation of the ecological impact emanating from urban drainage systems. The establishment of such network models, however, requires detailed and accurate information about the sewer network structure and the connected surface area. This infrastructure data is often unavailable, confidential or available in ‘paper’ format only. The present paper outlines a novel approach to develop a hydraulic sewer model constrained by a minimum amount of data. The approach combines the application of a surface flow accumulation algorithm to a selectively manipulated Digital Elevation Model (DEM) with a routine for hydraulic network dimensioning to generate a close-to-reality sewer network ready to be implemented in a hydraulic modelling platform. The method is tested for three real-life catchments of which characteristics vary in scale, topography, state of development and network complexity. For all cases the generated network is implemented on the EPA-SWMM platform to allow hydrodynamic simulations. Model performance is assessed by (1) evaluating the spatial match of existing and generated network layout, (2) comparing the estimated hydraulic dimension with real-life infrastructure data and (3) benchmarking simulated runoff with measured data for a defined validation period. The analysis shows that the presented method is capable of reproducing the original network layout, network length and corresponding discharge rates based on little, freely available information. Further research potential is identified to improve the hydraulic dimensioning and the application to complex systems that include control structures. The presented approach is useful to estimate the scope of drainage networks including layout and design (e.g. for preliminary planning in emerging areas) to screen existing networks and to identify critical spots where more precise information is required.     

Reactive monazite and robust zircon growth in diatexites and leucogranites from a hot,slowly cooled orogen: implications for the Palaeoproterozoic tectonic evolution of the central Fennoscandian Shield,Sweden

Monazite in melt-producing, poly-metamorphic terranes can grow, dissolve or reprecipitate at different stages during orogenic evolution particularly in hot, slowly cooling orogens such as the Svecofennian. Owing to the high heat flow in such orogens, small variations in pressure, temperature or deformation intensity may promote a mineral reaction. Monazite in diatexites and leucogranites from two Svecofennian domains yields older, coeval and younger U–Pb SIMS and EMP ages than zircon from the same rock. As zircon precipitated during the melt-bearing stage, its U–Pb ages reflect the timing of peak metamorphism, which is associated with partial melting and leucogranite formation. In one of the domains, the Granite and Diatexite Belt, zircon ages range between 1.87 and 1.86 Ga, whereas monazite yields two distinct double peaks at 1.87–1.86 and 1.82–1.80 Ga. The younger double peak is related to monazite growth or reprecipitation during subsolidus conditions associated with deformation along late-orogenic shear zones. Magmatic monazite in leucogranite records systematic variations in composition and age during growth that can be directly linked to Th/U ratios and preferential growth sites of zircon, reflecting the transition from melt to melt crystallisation of the magma. In the adjacent Ljusdal Domain, peak metamorphism in amphibolite facies occurred at 1.83–1.82 Ga as given by both zircon and monazite chronology. Pre-partial melting, 1.85 Ga contact metamorphic monazite is preserved, in spite of the high-grade overprint. By combining structural analysis, petrography and monazite and zircon geochronology, a metamorphic terrane boundary has been identified. It is concluded that the boundary formed by crustal shortening accommodated by major thrusting.     

Late Archean basement in the Bangenhuken Complex of the Nordbreen Nappe, western Ny-Friesland, Svalbard

The rocks of western Ny-Friesland, northern Svalbard, are part of a tectonostratigraphy including four thrust sheets, each composed mainly of orthogneisses overlain by younger metasedimentary rocks. Previous geochronological studies have shown that the orthogneisses are dominated by ca. 1750 Mya granitoids. This study of a quartz-monzonite in one of the thrust sheets, the Nordbreen Nappe, yields a single-zircon U-Pb ion-microprobe age of 2709 Ø 28 My. This is the oldest rock unit so far reported in the Svalbard Caledonides. However, age-determinations on detrital zircons in the metasediments of western Ny-Friesland have shown that Late Archean rocks were prominent sources. The new ages presented here provide the first evidence of a local source for these sedimentary rocks.     

Facies and development of the Meggen Reef (Devonian,West Germany)

In the course of an exploration program in 1965 in the subsurface of the southeastern Elspe Syncline (Sauerland, Rhenish Schiefergebirge) was discovered a Middle Devonian reef, unknown up to now. The foundation is not yet drilled. The Meggen Reef forms a bioherm-like table reef which is completely surrounded by basinal sediments. According to organisms, matrix and primary voids within the reef limestones 7 facies types can be distinguished. The reef core is built of stromatoporoids and crinoids, the reef flank types are characterized by corals and crinoids. The subsided reef is covered with thin, partly condensed pelagic limestones. At the same time in the adjacent basin the stratiform pyrite-sphalerite-barite ore of Meggen is deposited. At the end of Middle Devonian time the Meggen reef and the overlying pelagic limestones are brecciated and transected by numerous sedimentary dikes. As in the sedimentary dikes the same acid tuffs are occurring, which follow immediately above the pyrite-sphalerite-barite ore of Meggen, there is a close connection between submarine destruction of the Meggen Reef, acid tuff eruptions and ascent of metall-bearing hydrothermal solutions. The Meggen Reef is due to the compression while the Variscan orogeny is deformed to an overturned and thrusted anticline and itself is thrusted over from the adjacent basin facies. With respect to the development of diagenetic processes, the following stages are distinguished: (1) during reef growth, (2) between reef growth and sedimentary dike formation, (3) between sedimentary dike formation and Variscan deformation and (4) during Variscan deformation.     

SHORT COMMUNICATION EFFECT OF STANDARDIZATION ON FRAGMENT-BASED MEASURES OF STRUCTURAL SIMILARITY

Substructural fragment occurrence data are widely used as the basis for measures of inter-molecularstructural similarity.This paper investigates the effect of standardization on the effectiveness of suchmeasures using eight data sets for which both structural and biological activity data are available.Eightdifferent standardization methods are studied and it is shown that there is no significant difference in theeffectivenesses of the various methods;accordingly,any of them can be used for the calculation ofintermolecular structural similarity.     

SPM response to tide and river flow in the hyper-turbid Ems River

In this paper, we analyse the behaviour of fine sediments in the hyper-turbid Lower Ems River, with focus on the river’s upper reaches, a stretch of about 25 km up-estuary of Terborg. Our analysis is based on long records of suspended particulate matter (SPM) from optical backscatter (OBS) measurements close to the bed at seven stations along the river, records of salinity and water level measurements at these stations, acoustic measurements on the vertical mud structure just up-estuary of Terborg and oxygen profiles in the lower 3 m of the water column close to Leerort and Terborg. Further, we use cross-sectionally averaged velocities computed with a calibrated numerical model. Distinction is made between four timescales, i.e. the semi-diurnal tidal timescale, the spring–neap tidal timescale, a timescale around an isolated peak in river flow (i.e. about 3 weeks) and a seasonal timescale. The data suggest that a pool of fluid/soft mud is present in these upper reaches, from up-estuary of Papenburg to a bit down-estuary of Terborg. Between Terborg and Gandersum, SPM values drop rapidly but remain high at a few gram per litre. The pool of fluid/soft mud is entrained/mobilized at the onset of flood, yielding SPM values of many tens gram per litre. This suspension is transported up-estuary with the flood. Around high water slack, part of the suspension settles, being remixed during ebb, while migrating down-estuary, but likely not much further than Terborg. Around low water slack, a large fraction of the sediment settles, reforming the pool of fluid mud. The rapid entrainment from the fluid mud layer after low water slack is only possible when the peak flood velocity exceeds a critical value of around 1 m/s, i.e. when the stratified water column seems to become internally supercritical. If the peak flood velocity does not reach this critical value, f.i. during neap tide, fluid mud is not entrained up to the OBS sensors. Thus, it is not classical tidal asymmetry, but the peak flood velocity itself which governs the hyper-turbid state in the Lower Ems River. The crucial role of river flow and river floods is in reducing these peak flood velocities. During elongated periods of high river flow, in e.g. wintertime, SPM concentrations reduce, and the soft mud deposits consolidate and possibly become locally armoured as well by sand washed in from the river. We have no observations that sediments are washed out of the hyper-turbid zone. Down-estuary of Terborg, where SPM values do not reach hyper-turbid conditions, the SPM dynamics are governed by classical tidal asymmetry and estuarine circulation. Hence, nowhere in the river, sediments are flushed from the upper reaches of the river into the Ems-Dollard estuary during high river flow events. However, exchange of sediment between river and estuary should occur because of tide-induced dispersion.     

Simulation of green roof test bed runoff

Low Impact Development (LID) aims to mitigate the hydrological impacts of urbanization by replication of processes in natural catchments. Green roofs covered with vegetation and pervious substrate are one alternative among a wide range of LID tools. Water retention of green roofs depends on many factors (e.g. local climate), and measurements remain crucial in evaluating their performance. The simulation of green roof retention by a hydrological model is one option to evaluate their potential benefits before implementation. In this paper, we evaluated the ability of the recently introduced LID green roof module of the stormwater management model to replicate runoff from monitored green roof test beds under Nordic climate conditions. A parameter sensitivity analysis was conducted to identify calibration parameters. The model showed an overall acceptable performance, and the results indicated the importance of accurately estimating potential evapotranspiration rates for inter‐event periods, which is essential in representing the retention capacity regeneration. Copyright © 2015 John Wiley & Sons, Ltd.     

Modeling of groundwater flow at depth in crystalline rock beneath a moving ice-sheet margin, exemplified by the Fennoscandian Shield, Sweden

On-going geological disposal programs for spent nuclear fuel have generated strong demands for investigation and characterization of deep-lying groundwater systems. Because of the long time scales for which radiological safety needs to be demonstrated in safety assessment applications, an analysis of the hydrogeological performance of the geosphere system during glacial climate conditions is needed. Groundwater flow at depth in crystalline rock during the passage of an ice-sheet margin is discussed based on performed groundwater-flow modeling of two bedrock sites, Forsmark and Laxemar, in the Fennoscandian Shield, Sweden. The modeled ice sheet mimics the Weichselian ice sheet during its last major advance and retreat over northern Europe. The paper elaborates and analyzes different choices of top boundary conditions at the ice sheet–subsurface interface (e.g. ice-sheet thickness and ice-margin velocity) and in the proglacial area (presence or lack of permafrost) and relates these choices to available groundwater-flow-model hydraulic output and prevailing conceptual hydrogeochemical models of the salinity evolution at the two sites. It is concluded that the choice of boundary conditions has a strong impact on results and that the studied sites behave differently for identical boundary conditions due to differences in their structural-hydraulic properties.