Historical changes in channel network extent and channel planform in an intensively managed landscape: Natural versus human-induced effects

Abstract

Humans have become major geomorphological agents, effecting substantial change in the characteristics of Earth's physical landscapes. The agricultural Midwest of the United States is a region marked by pronounced human influence at the landscape scale. Humans undoubtedly have strongly influenced critical zone processes, including fluvial processes, in intensively managed agricultural landscapes, yet the exact nature of human alteration of these processes is unknown. This study documents historical changes in the extent of the stream channel network and in channel planform within the upper Sangamon River basin -an intensively managed agricultural watershed in Illinois. Results indicate that the modern channel network is nearly three times more extensive than the channel network in the 1820s. Most change in drainage density has occurred in headwater portions of the basin where numerous drainage ditches have been added to the network to drain flat uplands. No detectable change in channel position is evident between 1940 and 2012 along about 60% of the total length of the Sangamon River and its major tributaries. Nearly 30% of the total length exhibits change related to meander dynamics (cutoffs and lateral migration), whereas about 8% has changed as a result of channelization. Channelized sections typically remain straight for decades following human modification, supporting the notion that humans produce long-lasting catastrophic change in channel planform in this region. The findings confirm that humans are effective agents of morphological change in fluvial systems in this intensively managed watershed. Documenting human-induced versus natural changes in fluvial systems is important for evaluating how other critical zone processes in intensively managed landscapes have been affected by these changes. Humaninduced changes in channel extent and planform most likely have altered this landscape from one dominated by biogeochemical transformations and storage of water and sediment prior to agricultural development into one now characterized by enhanced fluxes of water, sediment, and nutrients.

River network evolution and fluvial process responses to human activity in a hyper-arid environment – Case of the Tarim River in Northwest China

“…Human activity has had a substantial influence on fluvial processes and even on the modification of river networks; numerous studies have investigated human impacts, emphasizing rivers in temperate and humid regions (e.g., Brooks and Brierley, 1997;Surian and Rinaldi, 2003;Liébault et al, 2005;Gregory, 2006;Wohl, 2006;Hoffman et al, 2010;Rhoads et al, 2015). With the accelerated expansion of human activities from temperate and humid environments into arid environments, many dryland rivers have already been strongly influenced by, or are under significant threat from, various human interventions such as land reclamation and flow regulation, which often have more significant potential to disturb hydrological (e.g., Jacobson et al, 1995;Schick, 1995;Tooth, 2000a;Mansur and Nurkamil, 2010;McDonald et al, 2013) and fluvial processes (e.g., Graf, 1978Graf, , 1979Ortega et al, 2014).…”

Impacts of environmental stressors on the water resources of intensively managed hydrologic systems

“…The USRB has undergone significant alterations from human activities. A study of the historic changes in the basin indicated that its channel network has been extended by over three times since 1820s, mainly during human settlement and by agricultural activities (Rhoads, Lewis, & Andresen, ). The same study showed that in 1820, the USRB was 90% prairie and 10% forest, with forested areas mainly found along the riparian zones.…”

“…Nearly 200,000 tons (0.83 tons/ha) of sediments reach the lake every year. In fact, Illinois Environmental Protection Agency issued eight warning alerts in 13‐year period (between 1979 and 1992) due to high nitrate concentration caused mainly by nonpoint source pollution (Rhoads et al, ). Studying how these anthropogenic stressors modify the surface and groundwater resources will facilitate the understanding of watershed processes and the current and future behaviour of the critical zone.…”

Critical Zone Structure in the Glaciated Interior Lowlands, Usa: A Conceptual Model From the Intensively Managed Landscape Critical Zone Observatory

“…These mature fluvial networks create landscape relief that provides energy for sediment transport down hillslopes and, ultimately in to stream networks (Abban et al, 2016). In contrast, fluvial networks in the USRB prior to intensive agriculture, were limited in extent and did not drain large areas of the upland surface (Rhoads et al, 2016). The limited landscape relief in the USRB likely contributes to lower rates of post-settlement alluvial deposition than in CCW ) and a fluvial suspended load dominated by near-channel sources rather than agricultural fields (Neal and Anders, 2015).…”