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Drainage: Hydrological Impacts Downstream
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Water Resources and Hydrological Systems, 2020
Land drainage is the practice of removing excess water from the land, and it is one of the most important land management tools for improving crop production in many parts of the world. Drainage systems may be broadly divided into surface drainage (comprising land grading and open ditches), shallow drainage (such as subsoiling to mechanically loosen the upper layer of soil), subsurface or groundwater drainage (buried perforated pipes or deep ditches), and the main drainage systems (commonly open channels) used to convey the drain water away.[1] Drainage will inevitably affect the pattern of water flows from the land and into the receiving watercourses. It is these downstream impacts of farmland drainage on the timing and magnitude of peak flows that are considered here, using the results of experimental studies and computer simulations, to present a coherent picture, and to answer most of the apparent anomalies and conflicts.
Introduction
Published in Oscar Osvaldo Marquez-Calvo, Advancing Robust Multi-Objective Optimisation Applied to Complex Model-Based Water-Related Problems, 2020
Drainage systems consist of a set of infrastructural elements (e.g., pipes, canals and hydraulic structures) installed in urban or rural areas to drain the excess runoff water produced by rainfall and that can lead to flooding. In combined systems, this infrastructure also collects the wastewater produced in the city and transports it to treatment plants or to receiving water bodies. These water systems have problems associated to planning and management. In particular, the problem under consideration is the optimal design of these systems, which consists in determining the appropriate diameter of the pipes under some restrictions associated to costs, slopes, and limiting velocities. In this case, uncertain variables are the estimation of rainfall extremes (Arnbjerg-Nielsen et al. 2013), the evolution of land use in a subcatchment leading to changes in runoff patterns, the changes of pipe roughness due to aging, reduction of effective diameter due to accumulation of sediments, etc. To determine the capacity of channels/pipes in a rural drainage system, uncertain variables include the roughness coefficient of the canals and the pervious area depression storage. To implement Best Management Practices which include, among others, bio-retention cells, porous pavement, vegetative swales, and green roofs, the uncertainties are the conductivity slope, the surface roughness, the vegetation volume, etc. Although all the uncertainties just mentioned belong to flow models, other models, for example water quality models, can have many more uncertainties (Willems 2008).
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Published in L.G. Wilson, Lorne G. Everett, Stephen J. Cullen, Handbook of Vadose Zone Characterization & Monitoring, 2018
Shallow perched systems may spread contamination, cause problems with structures, or interfere with agriculture. Drainage systems are installed to alleviate these problems. These systems cause gravity flow of perched ground water to a ditch or sump from which it is pumped out. This outflow can be sampled. Typical drainage systems include open ditches, tile lines, perforated pipes, synthetic sheeting, or even layers of gravel and sand. Depending on the design of the system, it may be possible to sample outflows which drain different land-use sites such as agricultural areas (Eccles and Gruenberg, 1978) and sanitary landfills (Wilson and Small, 1973).
An initial parameter estimation approach for urban catchment modelling
Published in Urban Water Journal, 2023
Siming Gong, James E Ball, Nicholas Surawski
The Alexandra Canal catchment is located south of the Sydney CBD area, Australia, with the total area of 11.50 kilometres square. The catchment is highly urbanised, inclusive of multiple land uses such as residential (approx. 40%), industrial (approx. 25%), road (approx. 10%), parkland (approx. 22%) and water body (approx. 3%). There are heterogeneous land cover types for both impervious and pervious features, including single dwelling, terrace, dense apartment, industrial plants with large impervious areas, and sizeable pervious areas of parkland and golf course. The drainage system of the catchment consists of subsurface pipes, pits, covered channels, open channels, culverts and flood mitigation structures. Shown in Figure 1 is the remote sensing image of the Alexandra Canal catchment with the location respect to continental Australia and within the greater Sydney region.
Risk-based analysis of a detention basin for urban runoff control
Published in Journal of Applied Water Engineering and Research, 2018
Detention basin is one type of stormwater retardation facility commonly used in urban areas for sustainable urban drainage systems. The prevalent design practice is, under a specified design frequency, to determine the storage capacity and outlet control to temporarily accommodate excessive surface runoff produced by the rainstorm. For any design storage capacity, the presence of various uncertainties implies that the detention facility cannot guarantee to serve its intended function at all times. There is a chance that randomly occurring storms could produce surface runoff with volume in excess of the design capacity, hence causing undesirable overflow. This study presents a risk-based design of detention basins by explicitly considering the trade-off between the cost of the detention basin and overflow volume. The statistical properties of overflow volume such as the mean and standard deviation are derived by considering the inherent randomness of rainstorm events and their magnitudes. The special feature of the suggested risk-based analysis framework is that no monetary damage relation with the overflow volume is used or needed. The trade-off decision considers directly the cost of the detention basin and the statistical characteristics of overflow volume. A decision criterion based on marginal cost is applied to facilitate the determination of ‘best’ design according to the designer's willingness-to-pay for one unit reduction of overflow volume.
Model predictive control of urban drainage systems: A review and perspective towards smart real-time water management
Published in Critical Reviews in Environmental Science and Technology, 2018
Nadia Schou Vorndran Lund, Anne Katrine Vinther Falk, Morten Borup, Henrik Madsen, Peter Steen Mikkelsen
Urban drainage systems were developed in the 1850s and their purpose at that time was to secure public hygiene and prevent flooding. From 1960s onwards, pollution loads and environmental impacts became a focus and WWTPs were expanded and upgraded to decrease the discharge of pollutants to natural water bodies. Since then, many governments and environmental protection agencies have implemented regulations to reduce the frequency and magnitude of CSO events, mainly through expansion of the pipe systems and construction of storage basins. On top of stricter legislation, recent research shows that cities are growing and becoming denser, while many parts of the world are expected to receive more intense rainstorms in the next decades (Arnbjerg-Nielsen et al., 2013; Kaspersen et al., 2017; Sørup et al., 2016). These developments force us to rethink how to manage stormwater and wastewater in the future. There are three different means of addressing the challenges of increased runoff and stricter legislation: Preventing stormwater from entering the urban drainage system, typically by using locally placed stormwater control measures (SCM) that utilize a combination of the hydrological processes storage, infiltration, evapotranspiration, and delayed runoff.Expanding existing structures in the combined sewer system, including pipes, basins, and overflow structures.Implementing more advanced control strategies for the combined sewer system, based on actuators such as pumps and moveable gates.