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We investigated the ability of the coupled ALS and ADCP data for capturing stream channel geometry. This was accomplished by examining the differences for mean stream channel properties between the ALS/ADCP DTM and the reference TS/ADCP DTM as well as for the uncorrected UALS/ADCP DTM and reference TS/ADCP DTM at three representative stages (Table 1). The first comparative stage represents the discharge during the ALS scan which was 10.4 m3/s and a stage of 7.6 m. The second stage represents the median observed discharge in the gauging record which was 13.5 m3/s at a stage of 7.8 m. The third stage represents the maximum observed discharge in the gauging record which was 20.0 m3/s at a stage of 8.1 m. As the ALS and the high-resolution ground surveys were combined with the same bathymetric information, any differences in the comparison are attributed to the differences between the non-submerged portions of the DTMs (i.e., ALS and TS).

Table 1

Stream properties calculated from DTMs based upon TS survey, corrected ALS, and uncorrected ALS and ADCP data at three water depths representing the stage during the ALS survey, median observed stage, and maximum observed stage

Stream channel propertyTS/ADCPALS/ADCPUALS/ADCPDifference (TS vs. ALS)Difference (TS vs. UALS)
Stage during ALS survey (m) 7.5 7.5 7.5 0.0 0.0 
Mean top width (m) 15.1 14.6 11.0 − 0.5 − 4.1 
Mean wetted perimeter (m) 17.3 17.0 13.6 − 0.3 − 3.7 
Mean cross-section area (m222.7 22.3 22.1 − 0.4 − 0.6 
Mean hydraulic radius (m) 1.3 1.3 1.6 0.0 0.3 
Median stage (m) 7.8 7.8 7.8 0.0 0.0 
Mean top width (m) 17.2 16.9 11.1 − 0.3 − 6.1 
Mean wetted perimeter (m) 19.5 19.4 14.0 − 0.1 − 5.5 
Mean cross-section area (m225.1 24.7 23.8 − 0.4 − 1.3 
Mean hydraulic radius (m) 1.3 1.3 1.7 0.0 0.4 
Maximum stage (m) 8.1 8.1 8.1 0.0 0.0 
Mean top width (m) 23.4 21.6 16.4 − 1.8 − 7.0 
Mean wetted perimeter (m) 25.8 24.3 19.5 − 1.6 − 6.3 
Mean cross-section area (m231.2 30.7 28.0 − 0.6 − 3.2 
Mean hydraulic radius (m) 1.2 1.3 1.4 0.1 0.2 
Stream channel propertyTS/ADCPALS/ADCPUALS/ADCPDifference (TS vs. ALS)Difference (TS vs. UALS)
Stage during ALS survey (m) 7.5 7.5 7.5 0.0 0.0 
Mean top width (m) 15.1 14.6 11.0 − 0.5 − 4.1 
Mean wetted perimeter (m) 17.3 17.0 13.6 − 0.3 − 3.7 
Mean cross-section area (m222.7 22.3 22.1 − 0.4 − 0.6 
Mean hydraulic radius (m) 1.3 1.3 1.6 0.0 0.3 
Median stage (m) 7.8 7.8 7.8 0.0 0.0 
Mean top width (m) 17.2 16.9 11.1 − 0.3 − 6.1 
Mean wetted perimeter (m) 19.5 19.4 14.0 − 0.1 − 5.5 
Mean cross-section area (m225.1 24.7 23.8 − 0.4 − 1.3 
Mean hydraulic radius (m) 1.3 1.3 1.7 0.0 0.4 
Maximum stage (m) 8.1 8.1 8.1 0.0 0.0 
Mean top width (m) 23.4 21.6 16.4 − 1.8 − 7.0 
Mean wetted perimeter (m) 25.8 24.3 19.5 − 1.6 − 6.3 
Mean cross-section area (m231.2 30.7 28.0 − 0.6 − 3.2 
Mean hydraulic radius (m) 1.2 1.3 1.4 0.1 0.2 

Negative differences indicate an underestimation of the stream channel property while positive differences indicate an overestimation.

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