Sediment mobility and bed armoring in the St Clair River: insights from hydrodynamic modeling

Abstract

The lake levels in Lake Michigan‐Huron have recently fallen to near historical lows, as has the elevation difference between Lake Michigan‐Huron compared to Lake Erie. This decline in lake levels has the potential to cause detrimental impacts on the lake ecosystems, together with social and economic impacts on communities in the entire Great Lakes region. Results from past work suggest that morphological changes in the St Clair River, which is the only natural outlet for Lake Michigan‐Huron, could be an appreciable factor in the recent trends of lake level decline. A key research question is whether bed erosion within the river has caused an increase in water conveyance, therefore, contributed to the falling lake level. In this paper, a numerical modeling approach with field data is used to investigate the possibility of sediment movement in the St Clair River and assess the likelihood of morphological change under the current flow regime. A two‐dimensional numerical model was used to study flow structure, bed shear stress, and sediment mobility/armoring over a range of flow discharges. Boundary conditions for the numerical model were provided by detailed field measurements that included high‐resolution bathymetry and three‐dimensional flow velocities. The results indicate that, without considering other effects, under the current range of flow conditions, the shear stresses produced by the river flow are too low to transport most of the coarse bed sediment within the reach and are too low to cause substantial bed erosion or bed scour. However, the detailed maps of the bed show mobile bedforms in the upper St Clair River that are indicative of sediment transport. Relatively high shear stresses near a constriction at the upstream end of the river and at channel bends could cause local scour and deposition. Ship‐induced propeller wake erosion also is a likely cause of sediment movement in the entire reach. Other factors that may promote sediment movement, such as ice cover and dredging in the lower river, require further investigation. Copyright © 2012 John Wiley & Sons, Ltd.

Patterns of Change in Metabolic Capabilities of Sediment Microbial Communities in River and Lake Ecosystems

“…The Saint Clair River is the direct outlet of Lake Huron, and it flows approximately 64 km in a southerly direction to Lake Saint Clair ( Figure 1 ) and forms part of the international boundary between Canada and the United States [ 4 ]. Sediments transported along the Saint Clair River substrate consist of eroding glacial clays and medium-to-coarse sands and gravels [ 2 , 36 – 38 ]. The river drops almost 1.5 m from the elevation of Lake Huron to that of Lake Saint Clair.…”

“…The river drops almost 1.5 m from the elevation of Lake Huron to that of Lake Saint Clair. It is a relatively straight channel with artificial structures, such as riprap and retaining walls, some narrow beaches, and vegetated cliffs [ 38 ].…”

Lake Sturgeon, Lake Whitefish, and Walleye Egg Deposition Patterns with Response to Fish Spawning Substrate Restoration in the St. Clair–Detroit River System

“…The St. Clair River is naturally deeper than the Detroit River, and much less sediment was removed to facilitate passage of large vessels. Thus, natural deposits of coarse substrate are still present throughout the St. Clair River (Foster and Denny 2009;Liu et al 2012). However, these deposits tend to be in deep, high-velocity areas where safety and gear limitations prohibit sampling efforts, such as at the head of the St. Clair River at Port Huron, Michigan.…”

Flume tests on fluvial erosion mechanisms in till‐bed channels

“…This extends to a large connecting channel of the Great Lakes, the St Clair River between Lake Huron and Lake Erie, where erosion of exposed till is a significant issue and testing of till erosion thresholds was necessary as part of an assessment, using hydraulic and morpho‐dynamic models, of the potential bed erosion affecting lake levels (Mier and Garcia ; Liu et al ., ). Predicting channel adjustments, mitigating adverse erosion effects from, for example, urbanization, modeling long‐term landscape development (Gran et al ., ) and understanding fluvial history and current influences on river dynamics (Liu et al ., ; Phillips and Desloges, ; Thayer et al ., ), all require greater understanding of the geomorphology of this type of river. A fundamental component is observing erosion mechanisms, and explaining and predicting erodibility of various glacially‐derived, cohesive boundary materials.…”

“…An important practical issue is that semi-alluvial rivers of this type, while constrained by the cohesive boundary materials at moderate flows, are likely to respond to extreme high flows and other exogenic changes in a manner, and at a rate, much like alluvial channels (Ashmore and Church, 2001;. This extends to a large connecting channel of the Great Lakes, the St Clair River between Lake Huron and Lake Erie, where erosion of exposed till is a significant issue and testing of till erosion thresholds was necessary as part of an assessment, using hydraulic and morpho-dynamic models, of the potential bed erosion affecting lake levels (Mier and Garcia 2011;Liu et al, 2012). Predicting channel adjustments, mitigating adverse erosion effects from, for example, urbanization, modeling long-term landscape development (Gran et al, 2013) and understanding fluvial history and current influences on river dynamics (Liu et al, 2012;Phillips and Desloges, 2015;, all require greater understanding of the geomorphology of this type of river.…”