Determining Wetlands Distribution, Lake Depths, and Topography Using Airborne Lidar and Imagery on the North Slope, Deadhorse Area, Alaska

Abstract

On the Alaskan North Slope, a permafrost-dominated coastal plain above the Arctic Circle, the ability of lakes to support a fish population is a function of water depth, and wetlands classification is highly dependent on soil saturation (and thus microtopography). Using a new airborne lidar instrument that combines laser ranging at near-infrared wavelengths for topography and green wavelengths for bathymetry, we flew a pilot study over a 490-km2 area south of Prudhoe Bay in August 2012 to measure surface topography at a density of about 20 points/m2 and water-body depths at a density of about 2 points/m2.

High-resolution digital elevation models, having vertical accuracies of a few centimeters, have been generated from the topographic laser data that was acquired at a 400 kHz pulse rate. These models and associated point clouds can be used along with high-resolution color-infrared imagery to map permafrost landscape features such as soil/ice polygons and pingos and identify microtopographic features that influence soil moisture and consequently wetlands distribution.

Bathymetric lidar data, acquired at a pulse rate of 36 kHz, can be used to produce elevation models for the water surface and the water bottom, allowing water depths to be determined for shallow, freshwater lakes and anastomosing stream channels. Water penetration to depths greater than 6 m has been achieved in lakes with reported turbidities ranging from 0.7 to 4.3 nephelometric turbidity units (NTU).

Topographic and bathymetric lidar data were used to establish the boundaries, measure water depths, and estimate total and incremental water volumes for 283 shallow lakes in the survey area having surface areas greater than about 0.8 ha. These lakes together are estimated to contain 20,343,051 m3 (5,374,064,326 gal) of water, of which 724,813 m3 (191,475,524 gal) is found in 83 lakes with depths greater than 1.5 m (5 ft) and 116,753 m3 (30,842,854 gal) is found in 38 lakes with depths greater than 2.1 m (7 ft).

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