The upstream extent of a river network : a review of scientific knowledge of channel heads

Abstract

A river channel is a linear feature with definable bed and banks created by erosion of water concentrated into persistent flow paths. A river starts at the channel head, which is the upstream-most point of concentrated water flow and sediment transport between definable banks that are spatially continuous downslope. The locations of individual channel heads are difficult to predict because of hillslope-scale differences in gradient, infiltration capacity, porosity and permeability, and cohesion, each of which influences flow paths and erodibility of near-surface materials. Understanding the state of knowledge regarding the initiation point of channels can be useful in a management context when assessing what features on the landscape constitute river channels. Therefore, the primary objective of this report is to concisely summarize the existing state of scientific knowledge regarding where river channels and channel networks begin in the landscape. The report draws on published studies from diverse regions within the United States and around the world but focuses on research summarized in English. This report introduces terms, reviews the processes related to channel initiation in different landscape settings, discusses field and remote identification of channel heads, and outlines the research needs for channel-head identification and for improving channel delineation.

Use of an Efficient Proxy Solution for the Hillslope‐Storage Boussinesq Problem in Upscaling of Subsurface Stormflow

“…It is known that the choice of derived stream network has a direct impact on the shape and size of derived hillslopes, and past research efforts have explored the feasibility of various derived networks (Lin et al, 2006;Montgomery & Dietrich, 1992) as well as the more fundamental difficulty of specifying precisely where a channel begins (Wohl, 2018). In this work, we select a stream network associated with a Strahler stream ordering number greater than one, which results in a dense network.…”

Field guide to identifying the upper extent of stream channels

“…This field guide is an applied extension of the E. Wohl (2018) channel-head literature review, which established a baseline understanding of the upper extent of channels. The approach for this field guide was to characterize the hillslope-to-stream-channel transition zone in seven of the eight regions of the U.S.…”

“…Previous field observations of channel heads fixated particularly on steep, mountainous landscapes in the western U.S. (E. Wohl 2018). Therefore, predictions of channel-head locations, mostly based upon slope and drainage area relationships, are also skewed to the western part of the U.S (E. Wohl 2018).…”

“…In areas with low slopes, dense vegetation, and subsurface flow, channel heads can have small or subtle headcuts (e.g., Figure 2, Central Great Plains ecoregion). These low-gradient landscapes can contain gradational or discontinuous channel heads where discontinuities in subsurface flow cause the stream channel to start and stop at multiple headcuts over some distance downstream (E. Wohl 2018). Field observations and channel heads in different regions of the U.S. are described throughout chapter 3.…”

“…Previous field observations of channel heads fixated particularly on steep, mountainous landscapes in the western U.S. (E. Wohl 2018). Therefore, predictions of channel-head locations, mostly based upon slope and drainage area relationships, are also skewed to the western part of the U.S (E. Wohl 2018). Because the development of predictive methods focused heavily on mountainous western landscapes, without additional field investigation, caution should be used when applying these relationships to other landscapes.…”