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Pine Creek region surface water resources assessment Vol 1 - Study report Vol 2 - Geotechnical report



Pine Creek region surface water resources assessment Vol 1 - Study report Vol 2 - Geotechnical report


Willing & Partners; Dames & Moore; Earl James & Associates


E-Publications; E-Books; PublicationNT; Report no. 55/1989







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Northern Territory Government

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Report no. 55/1989

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Attribution International 4.0 (CC BY 4.0)

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Northern Territory Government



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Technical Report WRD89055 Viewed at 15:07:05 on 29/07/2010 Page 38 of 45. 11 11.1 FLOOD ANALYSIS OF FINAL SITES RAFTS Runoff Routing Model Spillway flows at each fmal site were estimated using the RAFTS rainfall runoff model.The main feature of RAFrS is the ability to generate runoff hydrographs which when routed through the dam storage can account for flood attenuation effects. As in most numerical analysis, the correct perfonnance of any model should be validated against known data. For the study area, the historical database is effectively limited to streamflow and rainfall data for the McKinlay River. RAFrS model parameters were calibrated, or adjusted to reproduce historical flood behaviour. Model calibration was checked by flood frequency analysis at gauging stations where record length was sufficient RAFrS models were set up for each of the nine final damsite catchments. The calibrated model parameters were directly applied but with some variation to account for site specific conditions. A summary of the adopted parameters is presented in Table. 1 1.1. Further model validation was made by comparing RAFrS design flows for each damsite with estimates derived from independent, albeit simpler, techniques. Given the accuracy of the alternative methods, agreement with RAFrS model results was favourable. A comprehensive review of the model validation process is detailed in Volume 2 of the study report. Table 11.1 : RAFTS Calibrated parameters for final dam sites Parameter Adopted Value Comment Initial loss Omm Saturated catdunent conditions Continuing loss 2.5 mm/hr Based on volumetric match of recorded hydrographs Channel lag 0.5 hr/km Based on recorded catchment response Storage coefficient K varies Based on Aitken (1975) Storage linearity n 0.715 RAFrS default value 11.2 Design Flood Selection The selection of an appropriate design flood to size spillway requirements is based on several factors. Guidelines are available which assign design standards in accordance to the potential hazard posed by the reservoir (A.,,1\4COLD, 1986). The loss of life, social disruption, direct property damage and indirect losses such as power generation and water supply are considered in the selection process. Depending on the flood hazard assessment, a design flood ranging from 1 % AEP to the Probable Maximum Flood (PMF) is generally recommended. PINE CREEK REGION - SURFACE WATER RESOURCES ASSESSMENT Page 21