Determination of channel-morphology characteristics, bankfull discharge, and various design-peak discharges in western Montana

摘要: Stream-restoration projects using natural stream designs typically are based on channel configurations that can accommodate a wide range of streamflow and sediment-transport conditions without excessive erosion or deposition. Bankfull discharge is an index considered to be closely related shape, size, slope (channel morphology). Because the need for more information about relation between morphology bankfull discharge, U.S. Geological Survey (USGS), in cooperation with Montana Department Transportation Agriculture-Lolo National Forest, conducted study collect channel-morphology bankfull-discharge data at gaged sites use these improve current (2004) methods estimation various design-peak discharges ungaged sites. This report presents characteristics, 41 western Montana. Channel were determined active discontinued USGS streamflow-gaging The recurrence interval this ranged from 1.0 4.4 years median value 1.5 years. relations characteristics examined regression analysis. analyses showed only significant all peak either width cross-sectional area. most area estimated by application multiplier after determining 2-year site. multiplier, which ratio sites, 0.21 3.7 0.84. Regression drainage three ranges mean annual precipitation. results indicated both precipitation significantly (p values less than 0.05) discharge. Introduction Stream alterations have resulted adverse habitat changes many fish wildlife species contributed declines native populations (Peters, 1990). Projects restore channels their original condition increasingly being undertaken reverse those declines. Successful restoration altered stable requires under conditions. Over past 10 years, been developed (Rosgen, 1996) assess relative stability design configurations. A key proper determination discharge—an slope. Currently (2004), commonly approximated equations relate having basin climatic active-channel (Parrett Johnson, 2004). Estimates existing may error, however, because assumption equal not valid Previous studies some 2 (Leopold others, 1964; Rosgen, 1996; Moody Odem, 1999). recent southwestern (Bass, 1999) might improved inclusion depth, area, other as additional explanatory variables. generally highly correlated (flood discharges), presented Bass (1999) suggest analysis result estimates ranging flood 500-year flood. Studies Dunne Leopold (1978), White (2001), Cinotto (2003) strong was used recon2 Determination Channel-Morphology Characteristics, Discharge, Various Design-Peak Discharges Western naissance level infer onsite measurements within regions similar runoff characteristics. Regional characteristics—such width, area—and also useful reconnaissancelevel studies. Agriculture Forest Service-Lolo These then try discharges—annual intervals 2, 5, 10, 25, 50, 100, 200, 500 (various designpeak discharges)—at develop