School of Civil, Environmental and Mining Engineering

Postgraduate research

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Current and completed research by our postgraduate students.

Contact

Ana Catarina Limede Dos Santos Silva Singh

Phone: (+61 8) 6488 7359
Fax: (+61 8) 6488 1015


Start date

May 2013

Submission date

May 2015

Ana Catarina Limede Dos Santos Silva Singh

Thesis

Analysis of the residence times in an urban living stream to characterise nutrient attenuation under baseflow conditions

Summary

The first stage of the research project involves the study of the water residence time in a living stream which is part of an urban drainage system. The focus of the study is in determining the seasonal variation and the dependence of residence time on hydrological factors such as variations in flow velocity and groundwater interaction; and also variations in the hydrological regime of the living stream (duration and frequency of storm events). This dependence will be correlated with the observed reduction in nutrients loads.

In the second stage, the living stream will be characterised by the application of the generalised dimensionless Damkӧhler number, NE. This characterisation, compares the competition between hydrological and biogeochemical controls in the system (living stream), and gives an indication of how dependent a specific biogeochemical (attenuation) process is on hydrological regime shifts (in particular to variations in flow velocity). The calculation of NE will be based on the residence times, determined during the first stage of this research project, and on the kinetic rate constants determined for specific (dissolved) nutrient attenuation processes. The study will correlate specific NE with hydrological conditions under which the biogeochemical process is primarily kinetically controlled, thus allowing the related biochemical/physical reaction to take place, culminating in a temporary or permanent removal of a solute from the system.

Why my research is important

The application of stormwater BMPs such as detention/retention basins, wetlands and the retrofitting of channelized urban drain systems into living streams, are strategies adopted by WSUD (Water Sensitive Urban Design) to reduce the impact of nutrients, and pollutants in general, on the rivers’ ecosystems. These strategies contrast with the conventional method of discharging stormwater directly into the rivers/sea via drainage networks.

Currently, the priority of stormwater network engineers is to design drainage systems that effectively convey stormwater and/or groundwater away from properties to minimise the risk of flooding and maintain the integrity of the asset. The focus of restoring stormwater channels into living streams is primarily related with infrastructure protection achieving stabilized banks by reducing flow flashiness (Kaushal et al., 2008). Notwithstanding, previous studies have noted that living streams do have some capacity to attenuate nutrient loads via alteration of the residence time (Boulton, 2007; Bukaveckas, 2007; Kasahara & Hill, 2006; Roberts et al, 2007).

In trying to identify critical hydrological factors, such as a residence time/flow velocity thresholds, one of the aims of this research is to contribute to the understanding of how dependent the performance of these systems is on hydrological factors and also to develop guidance notes so that these hydrological factors are considered as design criteria for stormwater systems, to specifically promote or enhance the potentialities of the system (living stream) to attenuate specific nutrients.

The study of these hydrological factors will ultimately support the improvement of current and possibly new urban drainage design standards, in particular WSUD and related stormwater BMPs


 

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Thursday, 19 September, 2013 11:39 AM

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