The Monitoring and Analysis of Rainfall Excess for Hydrologic Modelling

Mahony, Michaela Bronte (2018) The Monitoring and Analysis of Rainfall Excess for Hydrologic Modelling. [USQ Project]


Abstract

This research aims to analyse discharge and loss predictions of lumped conceptual hydrologic models in the Gowrie Creek Catchment, and to determine the effect that rainfall losses and catchment imperviousness have on runoff. Hydrologic runoff routing models are used to predict runoff hydrographs and peak discharges in a catchment network to be used for infrastructure design purposes. Therefore, a reliable model and input parameters are needed to ensure these discharges are not over or underestimated. There are many available recommendations from reports including the ARR2016 document for input parameter values, hence selecting an appropriate value for a specific catchment can be difficult with so many conflicting reports. By not appropriately determining peak discharges, the infrastructure designed to withstand the flow may either fail during a storm event, or be built far too large, both causing potential substantial economic impacts.

RORB and the Watershed Bounded Network Model (WBNM) were used to model the hydrologic response of the Gowrie Creek Catchment to a range of design rainfall durations and frequencies. Upon comparing the results, noticeable differences in hydrograph shape, peak discharge magnitude, runoff depths and timing were observed. These differences are fundamentally caused by variances in each model’s nonlinear storage functions and their methods to describe the subcatchment flow paths.

A sensitivity analysis concluded that the Initial Loss variable is highly sensitive to change, and can quickly affect the depth of runoff and peak discharge produced. Continuing Losses were less sensitive for values close to zero, with a threshold of CL=4mm/hr established as the divide between non-sensitive and sensitive rates for this catchment. For future modelling in this catchment, a suitable Initial Loss-Continuing Loss model has been defined as 24.8mm IL – 1.1mm/hr CL. The level of imperviousness within a catchment can lead to higher rates of runoff and peak discharge. As a moderately sensitive variable, any changes within a basin must be accounted for to ensure the resulting peak discharge and hydrograph volumes are suitable for hydraulic infrastructure design.


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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Honours) (Environmental) Bachelor of Business (Management & Leadership)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Agricultural Engineering (1 Aug 2018 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Agricultural Engineering (1 Aug 2018 -)
Supervisors: Alam, Jahangir; Gillies, Malcolm
Date Deposited: 15 Sep 2021 05:53
Last Modified: 15 Sep 2021 05:53
URI: http://eprints.usq.edu.au/id/eprint/40660

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