EGL Ref: 9215 23 June 2022 Page 13 This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. FIGURE 9: WAIHI EARTHQUAKE HORIZONTAL SPECTRAL ACCELERATIONS FOR ROCK SITES 3.4. Hydrology Waihi receives on average 1500 to 3000 mm of rain per year making it one of the wetter regions in the North Island. NIWA provides statistical rainfall depths and intensities through their national high intensity rainfall database (HIRD by NIWA), based on monitoring sites across the region. For Waihi the latest information statistical estimates of rainfall depths and estimates for storm events based on historic data are included in Table 1 and Table 2 for different durations. Rainfall occurring in the Waihi area runs off into the Ohinemuri River and its tributaries. The Ohinemuri River flows to the west, past the Storage 2 and Waihi Township, along SH2 through the Karangahake Gorge, past Paeroa, into the Waihou River, which then flows out into the Firth of Thames near the Thames Township. The Ohinemuri River is without stopbanks in its natural channel as it passes the Waihi Operation Site. Flood estimates for a 100-year Average Recurrence Interval (ARI) event have been developed around the Waihi Operation Development Site and the TSFs are currently located above the 100-year flood extent. The flood extent is shown in Figure 10.
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