Characterizing Land Use Impacts on Channel Geomorphology and Streambed Sedimentological Characteristics

Abstract

Land use can radically degrade stream physical habitat via alterations to channel geomorphology and sedimentological characteristics. However, independent and combined influences such as those of agricultural and urban land use practices on channel geomorphology and substrate composition remain poorly understood. To further understanding of mixed land use influence on stream physical habitat, an intensive, 56 km hydrogeomorphological assessment was undertaken in a representative mixed land use watershed located in Midwestern USA. Sub-objectives included quantitative characterization of (1) channel geomorphology, (2) substrate frequency and embeddedness, and (3) relationships between land use, channel geomorphology, and substrate frequency and embeddedness. Channel geomorphology, and stream substrate data were directly measured at survey transects (n = 561) every 100 m of the entire 56 km distance of the reference stream. Observed data were averaged within five sub-basins (Sites #1 to #5) nested across an agricultural-urban land use gradient. Multiple regression results showed agricultural and urban land use explained nearly all of the variance in average width to depth ratios (R2 = 0.960; p = 0.020; n = 5), and maximum bank angle (R2 = 0.896; p = 0.052; n = 5). Streambed substrate samples of pools indicated significantly (p < 0.001) increased substrate embeddedness at agricultural Site #1 (80%) located in the headwaters and urban Site #5 (79%) located in the lower reaches compared to rural-urban Sites #2 to #4 (39 to 57%) located in the mid-reaches of the study stream. Streambed substrate embeddedness samples of riffles that ranged from 51 to 72% at Sites #1 and #5, and 27 to 46% at Sites #2 to #4 were significantly different between sites (p = 0.013). Percent embeddedness increased with downstream distance by 5% km−1 with the lower urban reaches indicating symptoms of urban stream syndrome linked to degraded riffle habitat. Collectively, observed alterations to channel morphology and substrate composition point to land use alterations to channel geomorphology metrics correlated with increased substrate embeddedness outside of mid-reaches where bedrock channel constraints accounted for less than 3% of substrate frequency. Results from this study show how a hydrogeomorphological assessment can help elucidate casual factors, target critical source areas, and thus, guide regional stream restoration efforts of mixed-land-use watersheds.

Integrated Water Resources Research: Advancements in Understanding to Improve Future Sustainability

“…Results further demonstrate the immense, globally transferrable value of the experimental watershed approach for municipal watersheds. Mixed land use influences on stream physical habitat was investigated by Zeiger and Hubbart [10] who directly measured channel geomorphology, and stream substrate composition every 100 m over 56 km (n = 561). Results showed that agricultural and urban land use explained nearly all the variance in average river width to depth ratios (R 2 = 0.960; p = 0.020; n = 5), and maximum bank angle (R 2 = 0.896; p = 0.052; n = 5).…”

A Case-Study Application of the Experimental Watershed Study Design to Advance Adaptive Management of Contemporary Watersheds

“…Such results suggest water quality and aquatic habitat degradation in Hinkson Creek is not limited to the activities and spatial extent of the city of Columbia, but rather is a complex watershed-scale issue involving integrated anthropogenic and natural processes. Similarly, a physical habitat assessment (PHA) showed that Hinkson Creek is altered by agricultural and urban land uses [104,105] that have also impacted macroinvertebrate assemblages in Hinkson Creek. This information was important in CAM discussions, considering macroinvertebrates are key species indicating general aquatic ecosystem status [55,106].…”

“…This information was important in CAM discussions, considering macroinvertebrates are key species indicating general aquatic ecosystem status [55,106]. Results from the PHA clearly identified agricultural and urban land use alterations to channel geomorphology [105]. Results also showed increased substrate embeddedness (e.g., 80% vertical embeddedness of pool habitats) in the agricultural headwaters and in the lower urbanized reaches of Hinkson Creek [105].…”

Hydrologic and ecological investigations in the School Branch watershed, Hendricks County, Indiana—Water years 2016–2018

“…As hydrology changes with land use, the amount of nutrients, sediment, or other anthropogenic contaminants entering waterways is also altered. Agricultural land has been linked to increases in nutrients and sediment in adjacent streams (Munn and others, 2018;Schmidt and others, 2019;Zeiger and Hubbart, 2019). To alleviate the effects of agricultural land use on freshwater systems, some agricultural producers have implemented conservation cropping practices such as no-till farming, use of cover crops when cash crops are not on the field, maintenance of riparian buffer zones, and precision application of nutrients.…”

“…Besides being beneficial to farmers, keeping nutrients and sediment out of waterways helps aquatic ecosystems, because excess nutrients can lead to eutrophication and excess sedimentation from eroding soils can cause loss of habitat and harm to some aquatic species. Sedimentation can result in the loss of heterogeneity in streams due to fine sediment filling in pools and embedding gravel and cobble substrate (Munn and others, 2018;Zeiger and Hubbart, 2019).…”