Field guide to identifying the upper extent of stream channels

Abstract

The upper extent of a channel is a transition zone from the hillslope to the beginning of the stream channel. Accurately and consistently identifying the upper extent of a channel in the field and locating where hillslope processes transition to stream-channel processes can be a difficult task. Physical characteristics located at the beginning of a channel (i.e., channel head), including geomorphic, sediment, and vegetation indicators, can vary significantly across different landscapes in the United States. Remote tools are useful for examining the upper extent of channels, but these re-mote tools have limitations for identifying the beginning of channels. Even as the resolution of remote data continues to increase, field observations are necessary to validate the remote data on the ground and to accurately and consistently identify and locate the transition from the hillslope to the stream channel. Use of a combination of remote and field evidence is likely the most successful strategy for identifying channel heads. This report presents a case study that demonstrates how a weight-of-evidence approach can combine field and remote evidence to locate the different parts of the transition and ultimately to identify the channel-head location.

National Ordinary High Water Mark Field Delineation Manual for Rivers and Streams : Interim Version

“…Many of these limitations will be improved with NHDPlus HR because lidar data will be used to update the data set. Rossi and David (2022) offer a detailed description of the use of online resources and field surveys to identify the upper extent of stream channels. The improvement in NHDPlus HR is shown by the increase in the number of mapped stream features, from 2.6 million in NHD to 30 million in NHDPlus HR (Moore et al 2019).…”