Predictions for the Hydrological Performance of the Parua Stream Dam

Smith, Callum (2021) Predictions for the Hydrological Performance of the Parua Stream Dam. [USQ Project]

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SMITH Callum dissertation_redacted.pdf

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Engineers rely heavily on empirical methods for the design of Dams and associated outlet structures. Over-estimating parameters can lead to increased costs and under-estimating parameters can lead to safety concerns. Previous investigations revealed that the Parua Stream Dam was designed using the Rational Method, with a catchment area less than one third the actual size of the catchment. It has also been proposed to harvest a number of pine plantations which has the potential to increase runoff. This presents a concern for the safety of the dam and the outlet structures in a significant storm event.

This dissertation aimed to assess the performance of the existing dam and outlet structures in order to provide information that could be used if remedial works are required. This was achieved by monitoring rainfall and water level data and calibrating TP-108 parameters in HEC-HMS to construct a more accurate model of the catchments response to rainfall. This has also allowed an evaluation of the regional TP-108 method and the method of gauging catchments to calibrate model parameters.

The investigation revealed that the TP-108 method over-predicted runoff due to initially classifying the soils of the Waipapa Group as group C soil, instead of a group A soil. The Calibrated models achieved a much better fit when compared to TP-108 models and the final calibrated parameters achieved an acceptable level of fit, when verified against all storm events. The spillway breached in all simulation runs for the 1% Annual Exceedance Probability (AEP) events based on historic and climate change rainfall scenarios and existing and post pine tree harvest cover conditions. This confirmed the dam has inadequate performance with respect to the original design specifications and New Zealand Society on Large Dams, Dam Safety Guidelines (NZSOLD, 2015).

The project identified several potential errors and limitations when using a model to represent catchment behaviour. It also presents recommendations to minimise these potential errors through more accurate topographic data, discharge monitoring of outlet structures and site-specific infiltration testing.

The project demonstrates acceptable levels of fit can be achieved through calibrated models using gauged data; however additional storm data is required to verify the results of the project.

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Item Type: USQ Project
Item Status: Live Archive
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 - 31 Dec 2021)
Supervisors: Foley, Joseph
Qualification: Bachelor of Engineering (Honours) (Civil)
Date Deposited: 03 Jan 2023 04:38
Last Modified: 26 Jun 2023 02:09
Uncontrolled Keywords: dams, parameters, empirical methods, outlet structure, catchment, rainfall, soil, spillway, dam safety, calibrated models

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