In small wadeable streams, the majority of the work is accomplished using the backpack-mounted HDSS system (Figure 1). When using the HDSS Backpack system, the surveyor moves in an upstream direction, following the thalweg of the stream. The backpack-mounted HDSS system features a GPS receiver, four high-definition video cameras with image stabilization and a multi-sensor water quality sampler. One camera is faced forward, one downward, one at the right back and one at the left bank. Water quality is measured by a backpack-mounted multi-sensor probe located near the bottom of the wading staff. The water quality measurements are collected at user defined intervals (typically every 50 to 100m) and at any sites of interest, such as incoming tributaries or outfall pipes.
In larger streams and small rivers, a HDSS Kayak system is used (Figure 2). When using the kayak-mounted HDSS system, the surveyor navigates in a downstream direction, following the thalweg of the stream. In wider river sections, multiple kayaks traverse the section in parallel tracks to ensure adequate coverage. The HDSS Kayak system consists of a sit-on-top kayak, a GPS receiver, three GPS-enabled video cameras (facing forward, left, and right 90°), a hull-mounted down-looking video camera, a flush-mounted depth sensor, and an multi-sensor water quality probe. Side-scan sonar is used to capture substrate and channel condition data in areas too deep or too turbid to accurately view with the hull-mounted video camera. The GPS data is combined with the depth and water quality data within a multiplexer and then is recorded onto a flash drive.
For both the backpack- or kayak-mounted HDSS systems, the GPS NMEA data string is recorded at approximately 1 second intervals (1 Hz). In the base configuration, the HDSS system’s GPS receivers have a horizontal accuracy less than 3 m (usually less than 1 m). Where required, RTK correction can be applied to the GPS positional information to improve accuracy to less than 3 cm. At the end of each survey day, all data including the video, water quality, side-scan sonar, and GPS track logs are saved to multiple external hard drives. The track log for the GPS signal is exported in GPX format and the data stored in a database. Later, the video is further post-processed using video editing software to create a single view that encompasses all video streams. Finally, all data is aligned with the GPS data, such that each data point is associated with Coordinated Universal Time (UTC) and location coordinate information.
The strength of the HDSS method is due in part to its standardized suite of stream corridor variables including stream bank, in-channel, and water quality variables. While the standard variables are highly useful, not all projects will require all of the same information collected. For example, standard water quality measurements include water temperature, dissolved oxygen, pH, and conductivity. Additional water quality variables can be added or substituted based on their availability and the projects requirements. Selection of the final stream conditions variables is important to insure wide applicability of the final data, but also that the data can effectively answer project specific questions.
Following is a list of variables that can be collected using the HDSS method. If additional variables are needed for your project, ask us how we can customize the process to provide you with the data you need.
|· Streambank condition||· Point source pollution locations|
|· Bank height||· Riparian diversity|
|· Bank angle||· Legacy trees|
|· Bank stability||· Large woody debris|
|· Surface protection||· Docks, boat ramps, bridges|
|· Bankfull level||· Utility line crossings|
|· Bank erosion potential||· Pipe intakes and outfalls|
|· Habitat type (pool/riffle/run)||· Water quality parameters|
|· Stream width||· Channel rugosity|
|· Water depth||· Sinuosity|
|· Velocity classes||· Surface water elevation|
|· Substrate||· Instream cover|
|· Substrate embeddedness||· Algal cover|