Ephemeral Stream Network Extraction from Lidar‐Derived Elevation and Topographic Attributes in Urban and Forested Landscapes

Abstract

We describe a new approach using lidar-derived elevation data to remotely map headwater streams in forested and urban landscapes, and address ongoing challenges with mapping small streams.ABSTRACT: Under-representations of headwater channels in digital stream networks can result in uncertainty in the magnitude of headwater habitat loss, stream burial, and watershed function. Increased availability of high-resolution (<2 m) elevation data makes the delineation of headwater channels more attainable. In this study, elevation data derived from light detection and ranging was used to predict ephemeral stream networks across a forested and urban watershed in the Maryland Piedmont USA. A method was developed using topographic openness (TO) and wetness index to remotely predict the extent of stream networks. Predicted networks were compared against a comprehensive field survey of the ephemeral network in each watershed to evaluate performance. Comparisons were also made to the U.S. Geological Survey National Hydrography Dataset (NHD) and a flow accumulation approach where a single drainage area threshold defined channel initiation. Although the NHD and flow accumulation methods resulted in low commission errors, omission errors were highest in these networks. The TO-based networks detected a larger number of ephemeral channels, but with higher commission error. Small ephemeral channels with less defined banks or originating at groundwater seeps were difficult to detect in all methods. Comparisons between forested and urban watersheds also highlight the difficulty of identifying headwater channels using topographic attributes in human-modified landscapes.

Stream Network Dynamics of Non‐Perennial Rivers: Insights From Integrated Surface‐Subsurface Hydrological Modeling of Two Virtual Catchments

“…Over the years, numerous DEM‐based terrain analysis algorithms and procedures have been developed to determine the potentially active stream network (Howard, 1994; Montgomery & Dietrich, 1988; Montgomery & Foufoula‐Georgiou, 1993; Orlandini et al., 2003; O’Callaghan & Mark, 1984; Tarboton, 1997), together with topographic and wetness indices (Barling et al., 1994; Beven & Kirkby, 1979; O’Loughlin, 1986) applied as indicators of the response of the catchment saturation to rainfall events. These topographic parameters have been shown to be useful to analyze the links between morphometric characteristics and field data regarding soil moisture and vegetation controls on the response to the catchment (Azarnivand et al., 2020b; Fagherazzi et al., 1999; Grabs et al., 2012; Metes et al., 2022; Rinderer et al., 2014). Recently, the analysis of morphometric characteristics has also been combined with the results of surveys in non‐perennial stream networks, trying to use topographic indices to predict the locations of channel heads or to find threshold values to distinguish between perennial and non‐perennial streams (Jensen et al., 2018, 2019; Senatore et al., 2021; Shaw et al., 2017).…”