Linking of 2D and Pipe hydraulic models at fine spatial scales

Linking of two-dimensional overland flow hydraulic models with one-dimensional storm water pipe models at very fine resolution is becoming a standard approach for urban flood investigations. This paper describes the application of such an approach to a variety of small, complex urbanised catchments in Australia and New Zealand. A benefit of this approach is that previously hidden information in terms of secondary flow paths and cross-flows become apparent, an outcome that is not possible with traditional 1D modelling tools. Generation of flood risk mapping is much simpler through the use of direct GIS interfaces to the model result files, making the modelling and presentation process much more transparent. The paper will describe the application of the models, the calibration approach and some specialised modelling techniques when working at such fine spatial resolution in urban environments.

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Enhanced DEM-based flow path delineation methods for urban flood modelling

Journal of Hydroinformatics ◽

10.2166/hydro.2012.275 ◽

2012 ◽

Vol 15 (2) ◽

pp. 568-579

Author(s):

J. P. Leitão ◽

D. Prodanović ◽

S. Boonya-aroonnet ◽

Č. Maksimović

Keyword(s):

Urban Areas ◽

Overland Flow ◽

Flow Path ◽

Flow Paths ◽

Urban Flood ◽

Bouncing Ball ◽

Digital Elevation ◽

Synthetic Test ◽

Water Accumulation ◽

Flooding Events

In order to simulate surface runoff and flooding, one-dimensional (1D) overland flow networks can be automatically delineated using digital elevation models (DEM). The resulting network comprises flow paths and terrain depressions/ponds and is essential to reliably model pluvial (surface) flooding events in urban areas by so-called 1D/1D models. Conventional automatic DEM-based flow path delineation methods have problems in producing realistic overland flow paths when detailed high-resolution DEMs of urban areas are used. The aim of this paper is to present the results of research and development of three enhanced DEM-based overland flow path delineation methods; these methods are triggered when the conventional flow path delineation process stops due to a flow obstacle. Two of the methods, the ‘bouncing ball and buildings’ and ‘bouncing ball and A*’ methods, are based on the conventional ‘bouncing ball’ concept; the third proposed method, the ‘sliding ball’ method, is based on the physical water accumulation concept. These enhanced methods were tested and their results were compared with results obtained using two conventional flow path delineation methods using a semi-synthetic test DEM. The results showed significant improvements in terms of the reliability of the delineated overland flow paths when using these enhanced methods.

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The Relevance of Grated Inlets within Surface Drainage Systems in the Field of Urban Flood Resilience. A Review of Several Experimental and Numerical Simulation Approaches

Sustainability ◽

10.3390/su13137189 ◽

2021 ◽

Vol 13 (13) ◽

pp. 7189

Author(s):

Beniamino Russo ◽

Manuel Gómez Valentín ◽

Jackson Tellez-Álvarez

Keyword(s):

Overland Flow ◽

Drainage System ◽

Critical Conditions ◽

Hydraulic Efficiency ◽

Storm Events ◽

Urban Resilience ◽

Urban Flood ◽

Drainage Systems ◽

Surface Drainage ◽

Intense Storm

Urban drainage networks should be designed and operated preferably under open channel flow conditions without flux return, backwater, or overflows. In the case of extreme storm events, urban pluvial flooding is generated by the excess of surface runoff that could not be conveyed by pressurized sewer pipes, due to its limited capacity or, many times, due to the poor efficiency of surface drainage systems to collect uncontrolled overland flow. Generally, the hydraulic design of sewer systems is addressed more for underground networks, neglecting the surface drainage system, although inadequate inlet spacings and locations can cause dangerous flooding with relevant socio-economic impacts and the interruption of critical services and urban activities. Several experimental and numerical studies carried out at the Technical University of Catalonia (UPC) and other research institutions demonstrated that the hydraulic efficiency of inlets can be very low under critical conditions (e.g., high circulating overland flow on steep areas). In these cases, the hydraulic efficiency of conventional grated inlets and continuous transverse elements can be around 10–20%. Their hydraulic capacity, expressed in terms of discharge coefficients, shows the same criticism with values quite far from those that are usually used in several project practice phases. The grate clogging phenomenon and more intense storm events produced by climate change could further reduce the inlets’ performance. In this context, in order to improve the flood urban resilience of our cities, the relevance of the hydraulic behavior of surface drainage systems is clear.

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Prediction limits of mobile phone activity modelling

Royal Society Open Science ◽

10.1098/rsos.160900 ◽

2017 ◽

Vol 4 (2) ◽

pp. 160900 ◽

Cited By ~ 1

Author(s):

Dániel Kondor ◽

Sebastian Grauwin ◽

Zsófia Kallus ◽

István Gódor ◽

Stanislav Sobolevsky ◽

...

Keyword(s):

Mobile Phone ◽

Spatial Scales ◽

Urban Environments ◽

Full Spectrum ◽

Left Behind ◽

Social Events ◽

Prediction Limits ◽

Spatio Temporal ◽

City Structure ◽

The City

Thanks to their widespread usage, mobile devices have become one of the main sensors of human behaviour and digital traces left behind can be used as a proxy to study urban environments. Exploring the nature of the spatio-temporal patterns of mobile phone activity could thus be a crucial step towards understanding the full spectrum of human activities. Using 10 months of mobile phone records from Greater London resolved in both space and time, we investigate the regularity of human telecommunication activity on urban scales. We evaluate several options for decomposing activity timelines into typical and residual patterns, accounting for the strong periodic and seasonal components. We carry out our analysis on various spatial scales, showing that regularity increases as we look at aggregated activity in larger spatial units with more activity in them. We examine the statistical properties of the residuals and show that it can be explained by noise and specific outliers. Also, we look at sources of deviations from the general trends, which we find to be explainable based on knowledge of the city structure and places of attractions. We show examples how some of the outliers can be related to external factors such as specific social events.

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Bi-directional Coupling of an Unstructured Triangular Meshes-based Integrated Hydrodynamic Model for Heterogeneous Feature-based Urban Flood Simulation

10.21203/rs.3.rs-375226/v1 ◽

2021 ◽

Author(s):

Guoqiang Peng ◽

Zhuo Zhang ◽

Tian Zhang ◽

Zhiyao Song ◽

Arif Masrur

Keyword(s):

Water Flow ◽

Urban Areas ◽

Overland Flow ◽

Coupled Model ◽

Flood Simulation ◽

Urban Flood ◽

Essential Condition ◽

Flow Processes ◽

Feature Based ◽

Heterogeneous Feature

Abstract Urban pluvial flash floods have become a matter of widespread concern, as they severely impact people’s lives in urban areas. Hydrological and hydraulic models have been widely used for urban flood management and urban planning. Traditionally, to reduce the complexity of urban flood modelling and simulations, simplification or generalization methods have been used; for example, some models focus on the simulation of overland water flow, and some models focus on the simulation of the water flow in sewer systems. However, the water flow of urban floods includes both overland flow and sewer system flow. The overland flow processes are impacted by many different geographical features in what is an extremely spatially heterogeneous environment. Therefore, this article is based on two widely used models (SWMM and ANUGA) that are coupled to develop a bi-directional method of simulating water flow processes in urban areas. The open source overland flow model uses the unstructured triangular as the spatial discretization scheme. The unstructured triangular-based hydraulic model can be better used to capture the spatial heterogeneity of the urban surfaces. So, the unstructured triangular-based model is an essential condition for heterogeneous feature-based urban flood simulation. The experiments indicate that the proposed coupled model in this article can accurately depict surface waterlogged areas and that the heterogeneous feature-based urban flood model can be used to determine different types of urban flow processes.

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Structural, Hydrologic, and Sediment Connectivity in a Shrub-Encroached and Restored Semiarid Grassland

10.5194/egusphere-egu21-12904 ◽

2021 ◽

Author(s):

Justin Johnson ◽

Jason Williams ◽

Phillip Guertin ◽

Steven Archer ◽

Philip Heilman ◽

...

Keyword(s):

Sediment Yield ◽

Soil Loss ◽

Rainfall Intensity ◽

Overland Flow ◽

Spatial Scales ◽

Structural Connectivity ◽

Post Treatment ◽

Semiarid Grassland ◽

Concentrated Flow ◽

Shrub Canopy

Shrub encroachment of semiarid grasslands is influenced by connected runoff and erosion patterns that preferentially accumulate resources under vegetated patches (canopy microsites) and deplete interspaces. Soil loss from dryland hillslopes results when areas of bare ground become structurally and functionally connected through overland flow. Although these patterns have been well-described, uncertainty remains regarding how these feedbacks respond to restoration practices. This study compared the structure and hydrologic function of a shrub-encroached semiarid grassland treated five years prior with the herbicide, tebuthiuron, to that of an adjacent untreated grassland. Through a series of hydrologic experiments conducted at increasing spatial scales, vegetation and soil structural patterns were related to runoff and erosion responses. At a fine scale (0.5 m2), rainfall simulations (120 mm&#183;h-1 rainfall intensity; 45 min) showed herbicided shrub canopy microsites had greater infiltration capacities (105 and 71 mm&#183;h-1 terminal infiltration rates) and were less susceptible to splash-sheet erosion (3 and 26 g sediment yield) than untreated shrub canopy microsites, while interspaces were statistically comparable between study sites. Concentrated flow simulations at a coarse scale (~9 m2) revealed that gaps between the bases of vegetation (i.e. basal gaps) > 2 mwere positively related to both concentrated flow runoff (r = 0.72, p = 0.008) and sediment yield (r = 0.70, p = 0.012). Modeled hillslope-scale (50 m2) runoff and erosion (120 mm&#183;h-1 rainfall intensity; 45 min) indicated less soil loss in the tebuthiuron-treated site (1.78 Mg&#183;ha-1 tebuthiuron; 3.19 Mg&#183;ha-1 untreated), even though runoff was similar between sites. Our results suggest interspaces in shrub-encroached grasslands continue to be runoff sources following herbicide-induced shrub mortality and may be indicators of runoff responses at larger spatial scales. In contrast, sediment sources are limited post-treatment due to lesser sediment detachment from sheet-splash and concentrated flow processes. Reduced sediment supplies provide evidence that connectivity feedbacks that sustain a shrub-dominant ecological state may have been dampened post-treatment. Our study also highlights the utility of simple measures of structural connectivity, such as basal gaps, as an indicator of hillslope susceptibility to increased runoff and erosion.

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Numerical analysis of coupled hydrosystems based on an object-oriented compartment approach

Journal of Hydroinformatics ◽

10.2166/hydro.2008.003 ◽

2008 ◽

Vol 10 (3) ◽

pp. 227-244 ◽

Cited By ~ 34

Author(s):

Olaf Kolditz ◽

Jens-Olaf Delfs ◽

Claudius Bürger ◽

Martin Beinhorn ◽

Chan-Hee Park

Keyword(s):

Numerical Solution ◽

Land Surface ◽

Overland Flow ◽

Drainage Basin ◽

Spatial Scales ◽

Shallow Water Equation ◽

Object Oriented ◽

Richards Equation ◽

Saturated Flow ◽

Flow Processes

In this paper we present an object-oriented concept for numerical simulation of multi-field problems for coupled hydrosystem analysis. Individual (flow) processes modelled by a particular partial differential equation, i.e. overland flow by the shallow water equation, variably saturated flow by the Richards equation and saturated flow by the groundwater flow equation, are identified with their corresponding hydrologic compartments such as land surface, vadose zone and aquifers, respectively. The object-oriented framework of the compartment approach allows an uncomplicated coupling of these existing flow models. After a brief outline of the underlying mathematical models we focus on the numerical modelling and coupling of overland flow, variably saturated and groundwater flows via exchange flux terms. As each process object is associated with its own spatial discretisation mesh, temporal time-stepping scheme and appropriate numerical solution procedure. Flow processes in hydrosystems are coupled via their compartment (or process domain) boundaries without giving up the computational necessities and optimisations for the numerical solution of each individual process. However, the coupling requires a bridging of different temporal and spatial scales, which is solved here by the integration of fluxes (spatially and temporally). In closing we present three application examples: a benchmark test for overland flow on an infiltrating surface and two case studies – at the Borden site in Canada and the Beerze–Reusel drainage basin in the Netherlands.

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Scale effect on overland flow connectivity at the plot scale

Hydrology and Earth System Sciences ◽

10.5194/hess-17-87-2013 ◽

2013 ◽

Vol 17 (1) ◽

pp. 87-101 ◽

Cited By ~ 6

Author(s):

A. Peñuela ◽

M. Javaux ◽

C. L. Bielders

Keyword(s):

Scale Effect ◽

Overland Flow ◽

Soil Surface ◽

Real Field ◽

Flow Paths ◽

Essential Information ◽

Elevation Data ◽

Distributed Hydrological Models ◽

Outflow Boundary ◽

Degree Of Filling

Abstract. A major challenge in present-day hydrological sciences is to enhance the performance of existing distributed hydrological models through a better description of subgrid processes, in particular the subgrid connectivity of flow paths. The Relative Surface Connection (RSC) function was proposed by Antoine et al. (2009) as a functional indicator of runoff flow connectivity. For a given area, it expresses the percentage of the surface connected to the outflow boundary (C) as a function of the degree of filling of the depression storage. This function explicitly integrates the flow network at the soil surface and hence provides essential information regarding the flow paths' connectivity. It has been shown that this function could help improve the modeling of the hydrograph at the square meter scale, yet it is unknown how the scale affects the RSC function, and whether and how it can be extrapolated to other scales. The main objective of this research is to study the scale effect on overland flow connectivity (RSC function). For this purpose, digital elevation data of a real field (9 × 3 m) and three synthetic fields (6 × 6 m) with contrasting hydrological responses were used, and the RSC function was calculated at different scales by changing the length (l) or width (w) of the field. To different extents depending on the microtopography, border effects were observed for the smaller scales when decreasing l or w, which resulted in a strong decrease or increase of the maximum depression storage, respectively. There was no scale effect on the RSC function when changing w, but a remarkable scale effect was observed in the RSC function when changing l. In general, for a given degree of filling of the depression storage, C decreased as l increased, the change in C being inversely proportional to the change in l. However, this observation applied only up to approx. 50–70% (depending on the hydrological response of the field) of filling of depression storage, after which no correlation was found between C and l. The results of this study help identify the minimal scale to study overland flow connectivity. At scales larger than the minimal scale, the RSC function showed a great potential to be extrapolated to other scales.

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Dietary choices in a generalist herbivore, the eastern cottontail Sylvilagus floridanus, in urban landscapes

Behaviour ◽

10.1163/1568539x-bja10071 ◽

2021 ◽

pp. 1-19

Author(s):

Mohammad A. Abu Baker ◽

Sara E. Emerson ◽

Jessica Gorman ◽

Joel S. Brown

Keyword(s):

Spatial Scales ◽

Urban Environments ◽

College Campuses ◽

High Protein ◽

Urban Landscapes ◽

Sylvilagus Floridanus ◽

Generalist Herbivore ◽

Left Behind ◽

Dietary Choices ◽

Midwestern Usa

Abstract We tested for dietary choices of foods varying in nutrient composition by cottontail rabbits on two college campuses in midwestern USA. We quantified choices among pellets of varying nutritional quality at artificial food patches. Dietary choices differed between seasons and locations. Spring giving-up densities (GUDs: food left behind) did not show differences in food choices and were lower than summer GUDs. In Appleton, the cottontails favoured both high protein and fibre pellets, whereas the medium protein and fibre pellets were favoured in Chicago. The cottontails maintained their choice of high protein, high fibre pellets at three spatial scales. The cottontails varied food intake to balance their protein, salt and fibre needs at different times and locations. Studying dietary choices and the effect of resource quality on foraging responses by urban wildlife provides a useful tool to study ecological interactions and can help minimize damage in urban environments such as parks.

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