Predicting Fill Time of a Gravel Extraction Site on a Reach of the Sagavanirktok River, Alaska, Using a Two-Dimensional Model

Abstract

During summer 2017, two parallel trenches were excavated in the Sagavanirktok River (located in northern Alaska, United States) to acquire construction material for roadwork on the Dalton Highway nearby. A study to estimate the time it would take for the trenches to fill with the upstream sediment was needed. In undertaking this study, we used three bed sediment transport equations for gravel-bed rivers available in the Sedimentation and River Hydraulics—Two-Dimensional model, with three hydrograph input scenarios: (1) normal cumulative volumetric flow; (2) maximum discharge; and (3) maximum cumulative volumetric flow. These scenarios, coupled with the three sediment transport equations, produced a total of nine simulations. Scenario 1 predicted a time to refill of 1–3.75 years based on the sediment transport equations used. Scenarios 2 and 3 predicted shorter times to refill. All three sediment transport equations predicted that sustained high flows are capable of refilling the trenches in 1 year. This is the first time that calculations have been made to estimate the refilling time of an extraction site on the Sagavanirktok River. These calculations could expedite the permitting process, eliminating the need for a new extraction site by returning to a site that has refilled with sediment. An indirect benefit of these calculations is that they provide information for fisheries biologists working in northern regions.