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4-33 <br />• of interest as long as the basin size is known, even if flood <br /> predictions have not been made for that size area in this <br />report. <br />4.5.3.3 Flood Hazards <br />4.5.3.3.1 General <br />Annual floods in the region are caused by both snowmelt and <br />thunderstorms; however, those peak flows associated with <br />thunderstorms are usually much higher than peak flows caused <br />by snowmelt. Thunderstorms do not occur in all basins every <br />year; therefore, the discharge records show annual peaks in <br />some years which are caused by snowmelt. <br />• Because thunderstorm peak flows are large, these flows are <br />of primary interest. Thunderstorms produce rainfall of short <br />duration and high intensity. The resulting floods have high <br />peak discharges of short duration. <br />4.5.3.3.2 Road Crossings <br />The potential flood hazards in the permit area are the access <br />road stream crossings, the waste rock disposal are and the mine <br />portal. The flood hazard to the access road is mitigated by <br />adequate sizing of the culverts. This has been the subject <br />of a separate report by R. V. Lord and Associates (see <br />Appendix C). This report concludes that the existing culverts <br />are capable of safely discharging the 10-year flood, or greater, <br />• without overtopping the road. <br />