Search NASA⌕ Search

SEARCH · Search NASA

Results for “Stream Channel Delineation”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Quantitative Methods for Comparing Different Polyline Stream Network Models

Two techniques for exploring relative horizontal accuracy of complex linear spatial features are described and sample source code (pseudo code) is presented for this purpose. The first technique, relative sinuosity, is presented as a measure of the complexity or detail of a polyline network in comparison to a reference network. We term the second technique longitudinal root mean squared error (LRMSE) and present it as a means for quantitatively assessing the horizontal variance between two polyline data sets representing digitized (reference) and derived stream and river networks. Both relative sinuosity and LRMSE are shown to be suitable measures of horizontal stream network accuracy for assessing quality and variation in linear features. Both techniques have been used in two recent investigations involving extracting of hydrographic features from LiDAR elevation data. One confirmed that, with the greatly increased resolution of LiDAR data, smaller cell sizes yielded better stream network delineations, based on sinuosity and LRMSE, when using LiDAR-derived DEMs. The other demonstrated a new method of delineating stream channels directly from LiDAR point clouds, without the intermediate step of deriving a DEM, showing that the direct delineation from LiDAR point clouds yielded an excellent and much better match, as indicated by the LRMSE.

58 GEOSCIENCES↗
DOE OSTI2015

Groundwater Discharge along a Channelized Coastal Plain Stream

In the Coastal Plain of the southeastern USA, streams have commonly been artificially channelized for flood control and agricultural drainage. However, groundwater discharge along such streams has received relatively little attention. Using a combination of stream- and spring-flow measurements, spring temperature measurements, temperature profiling along the stream-bed, and geologic mapping, we delineated zones of diffuse and focused discharge along Little Bayou Creek, a channelized, first-order perennial stream in western Kentucky. Seasonal variability in groundwater discharge mimics hydraulic-head fluctuations in a nearby monitoring well and spring-discharge fluctuations elsewhere in the region, and is likely to reflect seasonal variability in recharge. Diffuse discharge occurs where the stream is incised into the semi-confined regional gravel aquifer, which is comprised of the Mounds Gravel. Focused discharge occurs upstream where the channel appears to have intersected preferential pathways within the confining unit. Seasonal fluctuations in discharge from individual springs are repressed where piping results in bank collapse. Thereby, focused discharge can contribute to the morphological evolution of the stream channel.

58 GEOSCIENCES↗
DOE OSTI2016

Urban stream deserts: Mapping a legacy of urbanization in the United States

Protecting, as well as restoring, natural resources within the urban landscape has environmental and economic importance, especially as the global population continues to shift towards urban areas. One extreme legacy of rapid development and urbanization is stream burial. Riverless urban areas are mapped in 11 Megaregions within the United States, with additional focus on the Great Lakes, using a semi-automated, geoprocessing workflow completed within ArcMap10.2. Combining U.S. Census Bureau Urban Areas (UAs), Impervious Surface Coverage (ISC) from the 2011 National Land Cover Dataset (NLCD), and National Hydrography Dataset (NHD) flowlines, allowed the delineation of urban stream deserts (UrbSDs), or watershed areas where stream channels have likely been buried or removed. Approximately 6.2% of the area of UAs (or 11,490 km 2 ) within the 11 Megaregions are UrbSD, and they are most prevalent in major cities in the North California and Great Lakes Megaregions. Specifically, 537 UrbSD exist within the Great Lakes Megaregion, with Detroit (MI) and Chicago (IL) comprising some of the largest UrbSDs in the United States. Regardless of Megaregion, UrbSDs represent the most intensely urbanized components of the urban environment, as UrbSDs have higher population densities, impervious surface coverage and developed land uses than adjacent urban areas. UrbSD are unique, but poorly understood, components of the urban ecosystem that highlights the consequences of sacrificing longterm environmental sustainability (e.g., ecosystem services) for short-term economic growth (rapid development).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Mapping ephemeral stream networks in desert environments using very-high-spatial-resolution multispectral remote sensing

In this paper, understanding the spatial patterns of ephemeral streams is crucial for understanding how hydrologic processes influence the abundance and distribution of wildlife habitats in desert regions. Available methods for mapping ephemeral streams at the watershed scale typically underestimate the size of channel networks. Although remote sensing is an effective means of collecting data and obtaining information on large, inaccessible areas, conventional techniques for extracting channel features are not sufficient in regions that have small topographic gradients and subtle target-background spectral contrast. By using very high resolution multispectral imagery, we developed a new algorithm that applies landscape information to map ephemeral channels in desert regions of the Southwestern United States where utility-scale solar energy development is occurring. Knowledge about landscape features and structures was integrated into the algorithm using a series of spectral transformation and spatial statistical operations to integrate information about landscape features and structures. The algorithm extracted ephemeral stream channels at a local scale, with the result that approximately 900% more ephemeral streams was identified than what were identified by using the U.S. Geological Survey’s National Hydrography Dataset. The accuracy of the algorithm in detecting channel areas was as high as 92%, and its accuracy in delineating channel center lines was 91% when compared to a subset of channel networks that were digitized by using the very high resolution imagery. Although the algorithm captured stream channels in desert landscapes across various channel sizes and forms, it often underestimated stream headwaters and channels obscured by bright soils and sparse vegetation. While further improvement is warranted, the algorithm provides an effective means of obtaining detailed information about ephemeral streams, and it could make a significant contribution toward improving the hydrological modelling of desert environments.

47 OTHER INSTRUMENTATION↗