INTEGRATING REMOTE SENSING AND IN-SITU MEASUREMENTS TO PRODUCE A COST-EFFECTIVE BATHYMETRIC MAP OF HAVILAND LAKE IN DURANGO, COLORADO

Haviland lake is a small (~0.3 km²) reservoir north of Durango, Colorado, that has been drained to facilitate dam improvements over the past two years. The lake is currently being re-filled and may be undergoing sediment redistribution. To determine if sediment redistribution has occurred during inundation, we created a bathymetric map for Haviland Lake using a combination of remote sensing and in-situ measurement techniques. This combination creates a cost-effective methodology that can be used to produce bathymetric maps for other lakes within the southwestern United States.

With a fusion of sonar, RTK-GPS, UAV imagery and lidar, we were able to construct a bathymetric map of Haviland Lake after post-construction inundation. Sonar was collected using a Humminbird Helix 8 side-scan sonar to determine the depth of the lake bottom surface at water depths greater than 0.6 meters. RTK-GPS measurements were collected to obtain the elevation of the current lake water level, allowing us to transform bathymetry measured from sonar to absolute elevations. Structure-from-motion (SfM) photogrammetry using a DJI Mavic 2 Pro UAV was performed to measure the elevation of the subaerial and nearshore zones. Lidar data that was collected in 2019 was used to determine the elevation of the upland topography.

By combining these data sets, we were able to create a continuous digital elevation model (DEM) for Haviland Lake with elevations of the lake bottom and surrounding terrain. With the lowest spatial resolution being 0.3 meters for bathymetric measurements, this cost-effective alternative to traditional bathymetric studies provides insight into the redistribution and channelization of sediment along the south and west margins of the lake. This DEM also reveals that the shallow depths for the north and east margins of the lake were not significantly influenced by inundation. Additionally, we can compare the estimates of lake bottom depths produced by SfM to depths measured with sonar in order to determine their accuracy. Using this methodology of combining remote sensing with in-situ measurements can be useful in producing cost-effective bathymetric products with a high spatial resolution for other bodies of water.