Measuring bluff erosion part 2: Pairing aerial photographs and terrestrial laser scanning to create a watershed scale sediment budget

Stephanie S. Day, Karen B Gran, Patrick Belmont, Tim Wawrzyniec

Research output: Contribution to journalArticlepeer-review

47 Scopus citations

Abstract

Effectively managing and reducing high suspended sediment loads in rivers requires an understanding of the magnitude of major sediment sources as well as erosion and transport processes that deliver excess fine sediments to the channel network. The focus of this research is to determine the magnitude of erosion from tall bluffs, a primary sediment source in the 2880 km2 Le Sueur watershed, Minnesota, USA. We coupled analyses of seven decades of aerial photographs with four years of repeat terrestrial laser scanning (TLS) to determine erosion rates on bluffs. Together, these datasets provide decadal-scale retreat rates throughout the entire watershed and high-resolution geomorphic change detection on a subset of bluffs to both constrain erosion rates and document how environmental conditions affect bluff retreat. Erosion rates from aerial photographs and TLS were extrapolated from 243 and 15 measured bluffs, respectively, to all 480 bluffs in the Le Sueur watershed using multiple techniques to obtain estimates of sediment loading from these features at the watershed-scale. Despite different spatial and temporal measurement scales, the aerial photograph and TLS estimates yielded similar results for bluff retreat rate and total mass of sediment derived from bluffs, with bluffs in the Le Sueur watershed yielding 135 000±39 000 Mg/yr of fine sediment. Comparing this value to the average annual total suspended solids (TSS) load determined from gauging from 2000 to 2010, we determined that bluffs comprise 57±16% of the total TSS load, making bluffs the single most abundant fine sediment source in the basin.

Original languageEnglish (US)
Pages (from-to)1068-1082
Number of pages15
JournalEarth Surface Processes and Landforms
Volume38
Issue number10
DOIs
StatePublished - Aug 1 2013

Keywords

  • Aerial photographs
  • Bluffs
  • Erosion
  • Sediment budget
  • Terrestrial laser scanning

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