Linking morphodynamic response with sediment mass balance on the Colorado River in Marble Canyon: Issues of scale, geomorphic setting, and sampling design

• DOI: 10.1002/jgrf.20050
• Publication Date: 2013-02-26T19:40:39Z
• Authors: Paul E. Grams; David J. Topping; John C. Schmidt; Joseph E. Hazel; Matt Kaplinski
• Keywords: Hydraulics; Sedimentary budget

Abstract Measurements of morphologic change are often used to infer sediment mass balance. Such measurements may, however, result in gross errors when changes over short reaches extrapolated predict balance for long river segments. This issue is investigated by examination and influx efflux a 100 km segment the Colorado River Grand Canyon, Arizona. For each four monitoring intervals within 7 year study period, direction sand‐storage response was consistent with flux‐based sand Both budgeting methods indicate that storage stable or increased during period. Extrapolation outside does not, provide reasonable estimate magnitude area. results large errors, because there local variation site behavior driven interactions between flow bed topography. During same regime reach‐average supply, some locations accumulate while others evacuate sand. The interaction hydraulics channel geometry exerts more control on morphodynamic than supply an encompassing segment. Changes upstream modify responses but typically do not completely offset effect hydraulics. Thus, accurate budgets segments inferred from reach‐scale must incorporate sampling design avoid extrapolation altogether.