Geomorphology

Geomorphology is the study of the shape and features of landforms, how they are changing over time, and the processes that form and change them. It includes both morphological/topographic (land surface) and bathymetric (underwater) features. To better understand how our aquatic ecosystems are changing over time, NEON collects geomorphological data for streams, rivers and lakes at aquatic field sites.

Geomorphology provides insights into how surface and underwater landforms are changing and the factors that drive and influence these changes. On a geologic timescale, these processes include the movement of tectonic plates, volcanic activity and the movements of glaciers and ice sheets. On the shorter timescales of the 30-year NEON program, geomorphological processes include erosion of soil on riverbanks and lake shores caused by the action of water or wind, changes in water levels resulting from precipitation or snowpack melt, deposition of sediment carried by streams and rivers, vegetation growing on shore and underwater, sudden geologic events such as landslides or earthquakes, extreme weather events, and the impact of human activities on the physical features of streams, rivers and lakes.

The geomorphology of aquatic ecosystems impacts the microbial, plant and animal communities that live in or around surface water formations. The NEON project monitors changes in stream morphology, the underwater features of streams and lakes, and the composition, structure and vegetation patterns along the shorelines of streams (the riparian zone). By combining these data with associated observational and instrument data products, researchers will be able to examine important questions such as:

  • How are stream and lake morphology impacted by changes in precipitation patterns or temperature?
  • How are microbial communities in the water column and sediment layer impacted by changes in stream morphology or bathymetric features?
  • How is stream morphology related to the abundance and diversity of vegetation, macroinvertebrates or fish in aquatic ecosystems?
  • How does vegetation canopy cover over streams impact aquatic ecosystems?

Wadeable Stream Morphology Maps

The NEON program conducts surveys of wadeable streams once every five years or immediately following an extreme weather event. The resulting maps denote the topography of the stream channel, the location of the thalweg (the deepest part of the stream channel), and other features of interest including gravel or sand bars and coarse woody debris along the stream bank.

The survey covers approximately 500-1,000 m of the stream, an area known as the NEON aquatic reach. Fluvial geomorphology features are collected using a high-resolution robotic total station, an instrument used for land surveying. Benchmark points are mapped using a global positioning system (GPS) to tie the location to a known external reference. A prism pole is used to capture the location of geomorphology features such as major slope breaks in the channel and floodplain, water edges along channel banks, and habitat features.

The collected data are used to generate maps that provide a snapshot of fluvial characteristics at a particular point in time, including topographic features of the stream channel and floodplain, water surface elevation, and the location of channel features/biological habitats. The maps include:

  • Cross-sectional profile maps (floodplain width, bankfull width and streambed elevation)
  • Longitudinal profile maps (streambed topography, the location and position of in-stream biological habitat units including pool frequency and quality, in-channel large woody debris jams, mid-channel islands and bars, and water level elevation)
  • Pebble and large woody debris counts (quantifying the quality and distribution of in-channel substrate and wood)

The initial survey at each site establishes a baseline for stream topography and features. Subsequent surveys demonstrate how stream topography and structure have changed over time. After an extreme weather event such as a major storm, new data are collected as soon as possible to determine the impact of the event on stream morphology.

The stream morphology data product includes raw survey data, maps, shapefiles and metric tables delineating biological habitats within the aquatic reach boundaries. All data are openly available through the NEON data portal.

Data Products:

  • Stream Morphology Map

Bathymetric and Morphological Maps for Lakes and Non-wadeable Streams

Bathymetric and morphological surveys are conducted once every five years to characterize the underwater terrain of lakes and non-wadeable streams and rivers. This provides researchers with a detailed look at underwater geological formations and habitat features. The resulting maps include:

  • Depth maps
  • Sediment and substrate characteristics (e.g., sand, silt, clay, boulder, and bedrock)
  • Underwater habitat features include the distribution, abundance, and areal cover of flora and woody debris

High accuracy depth (bathymetric) maps are created with data obtained using hydroacoustic instruments mounted to a vessel. A differential GPS locates each measurement in space with a high degree of accuracy. Side-scan sonar is used to collect acoustic images of the substrate and underwater biota.

  • For lakes, the survey vessel is driven along the shoreline and in a gridded path that covers the entire lake surface.
  • For non-wadeable streams and rivers, the vessel is driven in a series of tracks parallel to the bank and covering the entire 1000 m longitudinal reach.

A baseline survey was completed for each lake or non-wadeable stream site. Subsequent surveys are completed at a minimum of every five years to monitor changes in lakes and stream bathymetry and morphology over time. These surveys are conducted once per year and are scheduled during the summer biological sampling period (bout 2) and within the "peak greenness" window for the field site. Additional surveys may be completed after an extreme weather event to assess resulting changes to the underwater terrain and habitat.

Data are reported with the temporal and spatial resolution of the collection event, including latitude, longitude, elevation, date and time. Summary data include volume and area calculations for the whole body of water (for lakes) or for specific bathymetric intervals (for rivers and streams) and areal calculations of habitat features. All data are openly available through the NEON data portal

Data products:

  • Bathymetric and morphological maps

Riparian Assessment

Riparian habitat assessment, which includes assessment of vegetation composition and physical structure, is completed at all NEON aquatic sites, including wadeable and non-wadeable streams or rivers and lakes. At wadeable streams, additional assessment of the percent of vegetation cover over the stream bed is conducted.

The riparian zone is the land area that exists at the interface of terrestrial and aquatic habitats. The zone NEON measures is a fixed width of ~50 m from the water’s edge. It includes the shoreline or banks of the body of water and the floodplain, extending from the water edge into the main terrestrial ecosystem. Riparian zones perform important ecosystem functions including soil stabilization and biofiltration, protecting aquatic environments from excessive runoff and soil erosion. They also provide important habitats and act as natural wildlife corridors, protecting diversity and abundance for both terrestrial and aquatic species.

Assessment of riparian composition and structure provides data related to riparian vegetation, bank characteristics and human impacts at NEON aquatic sites.

  • Assessment is conducted annually at "peak greenness" for each site.
  • For wadeable streams, observations are made within ten transects evenly spaced across the 500-1000 m aquatic reach. At larger rivers, five right bank and five left bank transects are surveyed. For lakes, ten approximately evenly spaced transects are established around the lake perimeter.
  • Riparian assessment transects are 20 m wide and extend up to 50 m from the shoreline or bank, depending on visibility from the water body.
  • Data collected include vegetation structure and composition and bank characteristics including bank angle, revetment, and bank texture.

At wadeable streams, additional data are collected to quantify the riparian canopy cover over the stream.

  • These data are collected at the same time and in the same transects as riparian composition and structure data for each wadeable stream site.
  • Percent canopy cover measurements are taken at three points for each stream transect (at stream center, 0.3 m from left bank, and 0.3 m from right bank) using densitometers.

All data are openly available through the NEON data portal.

Data products:

  • Riparian composition and structure (all NEON aquatic sites)
  • Riparian vegetation % cover (wadeable stream sites only)

Airborne Remote Sensing Data Products Related to Geomorphology Sampling

  • Elevation - LiDAR (NEON. DP3.30024)
  • Ecosystem Structure (NEON.DP3.30015)
  • High-resolution orthorectified camera imagery (NEON.DP1.30010)
  • High-resolution orthorectified camera imagery mosaic (NEON.DP3.30010)
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