Interactions between hyporheic flow produced by stream meanders, bars, and dunes

Abstract

[1] Stream channel morphology from grain-scale roughness to large meanders drives hyporheic exchange flow. In practice, it is difficult to model hyporheic flow over the wide spectrum of topographic features typically found in rivers. As a result, many studies only characterize isolated exchange processes at a single spatial scale. In this work, we simulated hyporheic flows induced by a range of geomorphic features including meanders, bars and dunes in sand bed streams. Twenty cases were examined with 5 degrees of river meandering. Each meandering river model was run initially without any small topographic features. Models were run again after superimposing only bars and then only dunes, and then run a final time after including all scales of topographic features. This allowed us to investigate the relative importance and interactions between flows induced by different scales of topography. We found that dunes typically contributed more to hyporheic exchange than bars and meanders. Furthermore, our simulations show that the volume of water exchanged and the distributions of hyporheic residence times resulting from various scales of topographic features are close to, but not linearly additive. These findings can potentially be used to develop scaling laws for hyporheic flow that can be widely applied in streams and rivers.

Channel Representation in Physically Based Models Coupling Groundwater and Surface Water: Pitfalls and How to Avoid Them

“…This approach relies either on the delineation of characteristic zones (e.g., bars vs. channels), on rules that define spatial patterns, or on process based models of erosion/deposition (see Koltermann and Gorelick 1996). Examples of topographic reconstruction applied to channels are provided by Legleiter et al (2011), Casas et al (2010b, and in the context of GSI modeling, by Stonedahl et al (2013).…”

Fractal patterns in riverbed morphology produce fractal scaling of water storage times

“…The exchange of water between surface and subsurface flows, generally termed hyporheic exchange, plays a critical role in structuring fluvial ecosystems [Boulton et al, 1998;Aubeneau et al, 2015]. Several studies have shown that fractal topography can produce scaling in hyporheic residence time distributions [Stonedahl et al, 2012[Stonedahl et al, , 2013Gomez-Velez and Harvey, 2014]. Worman et al [2006Worman et al [ , 2007 used numerical experiments to demonstrate the link between fractal topography and water storage times.…”

Scaling down hyporheic exchange flows: from catchments to reaches

“…Similar to the influence of bedrock geology at the catchment scale (Section 3.2), superficial sediments can significantly impact GSE via the HZ (Krause et al, 2012) and in turn influence overall hyporheic exchange flows and storage (e.g., presence of low conductivity streambed strata, Bencala, 1984;Harvey and Wagner, 2000;Buffington and Tonina, 2009;Angermann et al, 2012a;Stonedahl et al, 2013). At this scale, bed material caliber (grain size) expresses internal channel-20 forming mechanisms framed in the degree of confinement of the valley (Table 2).…”

“…Valley-floor and channel morphology control HEF in different ways depending on the valley type, which can be related generally to stream order because of covariations between channel constraints, channel planform morphology, and bedform sequences (Stonedahl et al, 2013;Kasahara and Wondzell, 2003) (Fig. 8).…”

“…High sinuosity rivers types (e.g., multi-thread or single/sinuous meandering) are less prone to a reduction of the hyporheic area with depth being able to maintain the HZ under largely losing and gaining conditions (Cardenas, 2009a) (Section 4.1- Table 2). Meander planimetry drives hyporheic flows and influences its residence times by creating 30 differences in the elevation head of surface water around a meander bend, with spatial and temporal variations as meanders evolve (Boano et al, 2006Revelli et al, 2008;Stonedahl et al, 2013). Naturally forced by the longitudinal head gradient, the hyporheic flows intrameander zone occur as river water infiltrates into the hyporheic zone at the upstream half of Hydrol.…”