Validation of the SCS TR-55 method on Whangarei District Watersheds and Soil Types

Jacobson, Matthew (2019) Validation of the SCS TR-55 method on Whangarei District Watersheds and Soil Types. [USQ Project]

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The design of hydraulic structures relies heavily on the estimation of rainfall generated runoff. The TR-55 method is widely used throughout the world by engineers and hydrologists. This is the method prescribed by the local council for use in the Whangarei District. Both local consulting engineers and the author have concerns over the suitability of TR-55 as no local validation has been undertaken, with flood levels often being estimated above any known events.

This research project aimed to assess the suitability of TR-55 in the Whangarei District. In particular, assessing where the primary local soil types fall into the method’s hydrologic soil groups and reviewing the Type IA rainfall distribution against known rainfall events.

Field investigations and flood frequency analyses of the gauged watershed were used to complete the critical tasks of the research, which also required the estimation of baseflow using the recursive digital filter technique by Lyne and Hollick.

The results of the research neither confirm or discount the suitability of the TR-55 method, but instead resulted in a set of recommendations and limitations for its use, with recommendations for further research. It was found that the TR-55 overestimated runoff by up to 327% and that the runoff characteristics of the major soil types in the Whangarei District were not well understood.

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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: Chowdhury, Rezaul
Qualification: Bachelor of Engineering (Honours) (Civil)
Date Deposited: 26 Aug 2021 01:24
Last Modified: 26 Jun 2023 22:36

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