Skip to main content
U.S. flag

An official website of the United States government

Validation of Elevation-derived Channels

By Center of Excellence for Geospatial Information Science (CEGIS)

We are developing methods for autonomous validation of elevation-derived hydrographic features using remote sensing data to update the NHD.

Introduction

The goal of this work is to develop methods for the improvement in accuracy and regular update of the National Hydrography Dataset (NHD). The NHD is an important dataset with applications including natural resource management, emergency response, and hydrologic modeling. In the past, the NHD was compiled from local hydrographic surveys and aerial photography with data collections dating from the 1940s to the present. More recent data collection approaches rely on deriving surface water drainage networks and other features from elevation data with interpretation from high-resolution photography or satellite image data. Apart from the variation in hydrographic patterns due to the vast range of geomorphic conditions across the United States, the NHD has heterogeneous coverage and resolution because of the various climate conditions and compilation standards that existed during the years of data collection.

Recent developments in remote sensing tools and methods have furnished opportunities to improve and continually update the NHD. For example, CEGIS researchers have used Digital Elevation Models (DEMs) and GIS in developing automated methods for mapping streams and comparing them to NHD. Results of the comparison indicate that the largest variance between automatically generated hydrography and NHD vector data is caused by missing headwater channels in the NHD. Areas of low topographic relief and heavy vegetation present the greatest challenge to synchronizing NHD to elevation-derived hydrography.

We are testing the use of lidar point clouds and other high-resolution optical data for identification and categorization of headwaters. Optical and lidar data collected with an Unmanned Aerial System (UAS) will be used in studies investigating the potential of high-resolution data fusion for modelling and for remote stream mapping.

 

Lidar-derived digital elevation model and NHD stream lines
Sources/Usage: Public Domain. View Media Details
The above image is a rendering of a lidar-derived digital elevation model of a low relief stream channel and associated National Hydrography Dataset line features in central Iowa. The low topographic relief makes flow accumulation modeling of surface water difficult. The digital models are being used to measure the structure of stream channels in an attempt to identify features that indicate the permanence of channels.(Public domain.)
lidar-derived digital surface elevation models of a stream channel
Sources/Usage: Public Domain. View Media Details
The above image is a rendering of a lidar-derived digital surface model overlaying a digital elevation model of a forested stream channel in central Iowa. The vegetation makes optical identification of the presence of water in channels difficult. The digital models are being used to measure the structure of vegetation adjacent to channels in an attempt to identify features that indicate the presence of surface water.(Public domain.)