Monitoring turbidity from above: Deploying small unoccupied aerial vehicles to image in‐stream turbidity

Abstract

Small unoccupied aerial systems (sUASs) are increasingly applied to study hydrologic processes and water quality. Here, we evaluate a novel application of sUAS to stream turbidity monitoring, with the goal of extending analyses implemented with satellite remote sensing to enable high resolution, rapid collection of turbidity imagery along smaller waterbodies. To accomplish this, we collected multispectral imagery using two sUAS platforms under a range of environmental conditions along a local creek in Syracuse, NY. In addition, we collected in situ turbidity observations immediately after each flight along several transects along the creek, as well as within a clear plume created by a natural spring entering the main channel of the creek. The in situ turbidity values were compared with the mean and standard deviation of several single‐band and multiband indices extracted along similar transects from the sUAS flights. On the basis of data collected across several flights, we found optical metrics obtained from multispectral imagery correlated well with in situ turbidity measurements. Though many optical metrics yielded strong relationships considering only values within the main channel, values associated with the red band were strongly related to turbidity estimates from the main channel as well as lower turbidity values observed in the spring plume. Although there are still limitations of this approach associated with variable field conditions, results from this proof of concept analysis show that sUASs offer a promising avenue for cost‐effective turbidity monitoring.

Investigating small unoccupied aerial systems (sUAS) multispectral imagery for total suspended solids and turbidity monitoring in small streams

“…A similar sUAS study was conducted on a small lake, but with coarser resolution of 0.2 m (Vogt and Vogt 2016). Recently, a turbidity sUAS multispectral study on a stream was conducted, with a range of turbidity measurements due to a natural spring and humaninduced sediment plume (Ehmann, Kelleher, and Condon 2019). This study only looked at individual bands or individual band ratios, did not incorporate depth-integrated sampling and did not maintain exact sampling locations.…”

Computational approaches for sub-meter ocean color remote sensing

“…Another example task that is limited by the current satellite-based ocean color sensor's spatio-temporal resolution combinations is the assessment of the spatial variability of turbidity in coastal regions on sub-meter scales [Luis et al, 2019]. A few specific examples where sub-meter data could be useful is in studying the impact of dredging [Ehmann et al, 2019], river outflow [IGOS, 2006], and glacial meltwaters [Wójcik et al, 2019] on local turbidity. In summary, algae and turbidity are two optical constituents that require measurement on sub-meter scales to assess their regional impact.…”

Measuring High Levels of Total Suspended Solids and Turbidity Using Small Unoccupied Aerial Systems (sUAS) Multispectral Imagery

“…Models were developed for each depth, but achieved limited coefficients of determination (r 2 ) values and significance. A similar study was conducted in a stream, measuring turbidity along with multispectral flights before and after a human-induced sediment plume [31]. No multi-variable modeling was performed; the focus was only to analyze single bands or single-band ratios.…”