Abstract

Bidirectional (hyporheic) exchange of water between stream channels and sediments benefits stream ecosystems, yet the effects of urbanization on such exchange are poorly understood. Exchange is controlled by a set of geomorphic parameters collectively defined as “hyporheic potential,” including sediment hydraulic conductivity (K), vertical undulations of the streambed (VC), and channel sinuosity (S). We measured these hyporheic potential metrics in 10 stream reaches with varying percent impervious surface (0–47 percent) in their contributing watersheds. We performed linear regression between hyporheic potential metrics and two metrics of urbanization: percent impervious in the watershed and average riparian forest buffer width. We found that most trends between hyporheic potential metrics and both urbanization metrics were noisy, with low r2. Furthermore, hyporheic potential varied as much among our streams as in non-urban studies, and K varied as much within stream reaches as between stream reaches. These results collectively indicate that the effects of urbanization on hyporheic potential in our streams were minimal and that urbanization may not heavily constrain hyporheic exchange. Nevertheless, we did find that S increased with impervious cover in the contributing watershed, consistent with higher urban storm flows leading to sinuosity adjustments to reduce channel slope. Urbanization may therefore enhance hyporheic potential under certain circumstances, and bears further study. Furthermore, there may be value in increasing the benefits of hyporheic exchange above existing levels through “hyporheic enhancement.” Because K varied more among streams than VC, which varied more than S, efforts to enhance hyporheic exchange may have greatest effect if they manipulate K.

You do not currently have access to this article.