Stream geomorphology in a mountain lake district: hydraulic geometry, sediment sources and sinks, and downstream lake effects

Abstract

Lakes are common in glaciated mountain regions and geomorphic principles suggest that lake modifications to water and sediment fluxes should affect downstream channels. Lakes in the Sawtooth Mountains, Idaho, USA, were created during glaciation and we sought to understand how and to what extent glacial morphology and lake disruption of fluxes control stream physical form and functions. First, we described downstream patterns in channel form including analyses of sediment entrainment and hydraulic geometry in one catchment with a lake. To expand on these observations and understand the role of glacial legacy, we collected data from 33 stream reaches throughout the region to compare channel form and functions among catchments with lakes, meadows (filled lakes), and no past or present lakes. Downstream hydraulic geometry relationships were weak for both the single catchment and regionally. Our data show that downstream patterns in sediment size, channel shape, sediment entrainment and channel hydraulic adjustment are explained by locations of sediment sources (hillslopes and tributaries) and sediment sinks (lakes). Stream reaches throughout the region are best differentiated by landscape position relative to lakes and meadows according to channel shape and sediment size, where outlets are wide and shallow with coarse sediment, and inlets are narrow and deep with finer sediment. Meadow outlets and lake outlets show similarities in the coarse-sediment fraction and channel capacity, but meadow outlets have a smaller fine-sediment fraction and nearly mobile sediment. Estimates of downstream recovery from lake effects on streams suggest 50 per cent recovery within 2-4 km downstream, but full recovery may not be reached within 20 km downstream. These results suggest that sediment sinks, such as lakes, in addition to sources, such as tributaries, are important local controls on mountain drainage networks.

Distribution and biophysical processes of beaded streams in Arctic permafrost landscapes

“…Additional locations were later selected to better refine this transition including identification of sediment sinks (flow-through lakes) or clear-water inputs (lakefed tributaries) relative to potential sediment sources including contact points with hillslopes and sand dunes, and tributaries originating from DTLBs or upland tundra. Such local controls on delivery of new water and sediment to channels were expected to help explain changes in form downstream, similar in concept to mountain drainage networks flowing through lakes (Arp et al, 2007) and as hypothesized for Arctic drainage networks (Tarbeeva and Surkov, 2013). The total length of channels analyzed for the Fish Creek watershed was about 135 km and the total length of channels analyzed for the Ublutuoch River watershed was about 70 km.…”

“…In contrast, surrounding tundra snowpack rarely exceeds 40 cm depth by late winter. Not only does this thick snowpack insulate ice and soil, but it also persists much longer in the spring and contributes a much larger portion of snow-water per unit area directly to runoff (Arp et al, 2010). From 12 beads we surveyed from 2010 to 2013, only one was found to be entirely frozen to the bed by March or April (Fig.…”

“…Examples of reach-scale water velocity distributions (reach length/travel time) measured using hydrologic tracer tests (rhodamine WT pulse additions) shown as cumulative tracer recovered downstream. Results from two beaded streams, Crea Creek (blue squares) and Blackfish Creek (red triangles) are compared to an alluvial stream (black circles) in a mountain meadow (Arp unpublished data, stream described in Arp et al, 2007); all three streams had similar discharges ranging from 85 to 140 L s −1 during tracer tests and slopes ranging from 0.1 to 0.2 %, but with otherwise differing morphologies (experimental data and inverse modeling results shown in Table 3). …”

Discontinuities in stream nutrient uptake below lakes in mountain drainage networks

“…Recent work has integrated the SDC and PDC by showing that because natural lakes function as sediment sinks they create abrupt transitions downstream in channel geometry and sediment mobility (Arp et al 2007). A larger body of work on ecological characteristics of streams below lakes also has demonstrated an abrupt transition in sourcewater characteristics (Magnuson and Kratz 2000) and biological processes (Robinson and Minshall 1990;Vadeboncoeur 1994;Marcarelli and Wurtsbaugh 2006).…”

Channel adjustments in response to the operation of large dams: The upper reach of the lower Yellow River

“…Due to the utility of at-a-station hydraulic geometry exponents for predicting alluvial channel behavior or discriminating different types of channel crosssection or pattern (Knighton, 1974(Knighton, , 1975Richards, 1976;Ferguson, 1986;Ellis and Church, 2005;Beyer, 2006;Arp et al, 2007;Nanson et al, 2010), at-a-station hydraulic geometry relations are used here to differentiate channel morphological adjustment up to the bankfull stage.…”