Channel head response to anthropogenic landscape modification: A case study from the North Carolina Piedmont, USA, with implications for water quality

Abstract

European-American settlement of the south-eastern United States introduced agricultural practices that included extensive clearing of forested hillslopes to support food and cash-crop agriculture. This land disturbance has long-term effects on stream morphology by displacing channel heads down-valley, impacting downstream sediment and nutrient supply as channel heads migrate back up-valley towards their pre-disturbance locations. This study investigates 40 stream channels in William B. Umstead State Park in the Piedmont of North Carolina using relationships between local slope and contributing drainage areas to predict channel head locations and compare these to their observed positions. Further, expected eroded sediment and nutrient contributions are quantified using migration distances and sampled soils near channel heads. Of the 40 investigated channel heads, 23 are located down-valley from their predicted location by an average of 174.4 m AE 109.6(1 À σ). Using this distance and average channel cross-sectional area, 1.6 AE 1.4 m 2(1 À σ), the expected future erosion per channel is 282.6 AE 177.6 m 3 (1 À σ).Drainage density was used to extrapolate volumes to the 23 km 2 park using a conservative estimate that 50% of the first-order channel heads will migrate up-valley, implying an additional 90.4 AE 56.8 Â 10 3 m 3 (1 À σ) of sediment is expected to erode from the study area. Finally, scaling these volume estimates to sampled soil nutrient values indicates that approximately 1053 AE 662 t (68% confidence) of carbon, 51 AE 32 t of total nitrogen, and 15 AE 9 t of phosphorus are anticipated to enter the fluvial system in response to channel head migration from within the confines of this state park, representing only 1% of the land area in Wake County. These findings suggest that regional water quality challenges posed by suspended sediments and nutrients will persist for hundreds to perhaps thousands of years from non-point sources as first-order channels continue to erode headward towards their equilibrium landscape positions.

Introduction to the Women in Geomorphology special issue

“…• watershed restoration and management, including human alterations of process and form (Atkins et al, 2023;Davis et al, 2021;Goodman et al, in press;Gurnell et al, 2022;Hinshaw et al, 2022;Mossa & Chen, 2022;Sampietro-Vattuone et al, 2021;Valentine et al, 2022); and…”

“…Field (26) Atkins et al, 2023;Bernatek-Jakiel & Nadal-Romero, 2023;Biausque et al, 2022;Brooks et al, 2022;Bywater-Reyes et al, 2022;Chin, 2022;Gervasi et al, 2021;Glover et al, 2022; Goodman et al, in press;Guiney & Lininger, 2022; Gurnell et al, 2022;Harvey et al, 2022;Hinshaw et al, 2022;Hooke, 2022;Konlechner & Hilton, 2022;Kooijman et al, 2022;Lane et al, 2022;Lefebvre et al, 2022;Marchetti et al, 2022;McKeon et al, 2022;Mol & Grenfell, 2022;Mossa & Chen, 2022;Opalka et al, 2022;Patton et al, 2022;Quock et al, 2022;Regalla et al, 2022;Reitman et al, 2022;Sampietro-Vattuone et al, 2021;Schoch-Baumann et al, 2022;Souza Fonseca et al, 2022;Spiske et al, 2022;Thompson et al, 2022;Uphues et al, 2022;Valentine et al, 2022;Van Soest et al, 2022;Wohl, 2022;Zhang et al, 2022 (Continues)…”

“…Many of the major research directions in contemporary geomorphology are reflected in this collection of papers. With respect to fluvial environments, including alluvial fans, individual papers examine use of images to detect sediment motion during physical experiments (Vah et al, 2022); comparison of grain‐size distributions from field measurements and remotely acquired images (Marchetti et al, 2022); physical experiments on bedload saltation under differing conditions (Demiral et al, 2022); numerical modelling of critical shear stress for grain entrainment based on imagery of bed‐rock channels (Hodge & Buechel, 2022); biogeomorphology (Bywater‐Reyes et al, 2022; Gurnell et al, 2022); channel morphology and classification (Lane et al, 2022), hydromorphology of ephemeral streams (Rabanaque et al, 2022) and interpretation of geomorphic unit assemblages (Fryirs & Brierley, 2022); flood effectiveness (Gervasi et al, 2021); channel evolution, terraces and sediment sources (Guyez et al, 2022) and the influence of sediment supply on gravel‐bed river widening (Rachelly et al, 2022); hydrological variation and meander morphodynamics (Hooke, 2022); the dynamics of wood in river corridors (Guiney & Lininger, 2022; Gurnell et al, 2022; Wohl, 2022) and numerical modelling of wood‐related processes (Friedrich et al, 2022); numerical model validation (Negreiros et al, 2022) and numerical modelling of groundwater‐driven network evolution (Cullen et al, 2022); base‐level controls and landscape evolution (Fadul et al, 2022); long‐term dryland channel response to urbanization (Chin, 2022); watershed restoration and management, including human alterations of process and form (Atkins et al, 2023; Davis et al, 2021; Goodman et al, in press; Gurnell et al, 2022; Hinshaw et al, 2022; Mossa & Chen, 2022; Sampietro‐Vattuone et al, 2021; Valentine et al, 2022); and alluvial fan dynamics (Opalka et al, 2022; Quock et al, 2022; Regalla et al, 2022; Schoch‐Baumann et al, 2022). Papers addressing process and form in coastal environments include examinations of dune morphodynamics and evolution (Hovenga et al,...…”

“…Understanding of geomorphic process and form is also commonly applied to management and restoration, as reflected in this collection with respect to fluvial (Atkins et al, 2023; Davis et al, 2021; Friedrich et al, 2022; Fryirs & Brierley, 2022; Goodman et al, in press; Gurnell et al, 2022; Hinshaw et al, 2022; Mossa & Chen, 2022; Rachelly et al, 2022; Sampietro‐Vattuone et al, 2021; Valentine et al, 2022) and coastal (Konlechner & Hilton, 2022; McKeon et al, 2022) environments.…”