IMPACT OF VARIED DATA RESOLUTION ON HYDRAULIC MODELING AND FLOODPLAIN DELINEATION¹

Abstract

Current data collection technologies such as light detection and ranging (LIDAR) produce dense digital terrain data that result in more accurate digital terrain models (DTMs) for engineering applications. However, such data are redundant and often cumbersome for hydrologic and hydraulic modeling purposes. Data filtering provides a means of eliminating redundant points and facilitates model preparation. This paper demonstrates the impact of varied data resolution on a case study completed for a 2.3 mi2 area with mild slopes (about 001 ft/ft) along Leith Creek near Laurinburg, North Carolina. For the original data set and seven filtered data sets, filtering induced changes in elevation, area, and hydraulic radius were determined for 10 water depths at 23 cross sections. Water surface elevations resulting from HEC‐RAS (Hydrologic Engineering Center‐River Analysis System) models for each data set were then compared. A hydraulic model sensitivity analysis was also conducted to compare filtering error to error introduced by variation in flow rates and roughness values. Finally, automated floodplain delineation was performed for each filter level based on the computed hydraulic model results and the filtered LIDAR elevations. Data filtering results indicate that significant time savings are achieved throughout the modeling process and that filtering to four degrees can be performed without compromising cross‐sectional geometry, hydraulic model results, or floodplain delineation results.

Mapping Topography Changes and Elevation Accuracies Using a Mobile Laser Scanner

“…After the integration of a scanning mechanism with lidar and an inertial measurements unit with GPS in the early 1990s, it has been possible to use first airborne laser scanning (ALS), then MLS data, in addition to static based terrestrial laser scanning (TLS), to improve the measurement and modeling of fluvial environments (e.g., [2][3][4][5][6][7][8][9][10][11][12]). High-resolution ALS provides detailed information on topographical features of fluvial environments that influence the river hydraulics, giving, therefore, the potential to improve existing hydraulic models (e.g., [13][14][15][16][17]). Furthermore, TLS can be applied to measure the grain-scale surface roughness needed in river flow modeling.…”

Modeling and visualizing uncertainties of flood boundary delineation: algorithm for slope and DEM resolution dependencies of 1D hydraulic models

“…Therefore, it is of interest to see how much the original laser data can be filtered, without losing predictability performance. For an area around Leith Creek, North Carolina, Omer et al (2003) looked at the angle a between two surveyed data points (Fig. 1).…”

“…1 Angle used to determine if point should be filtered away or kept in the DEM (cf. Omer et al 2003) surveyed data, 5 m contour data (scale 1:5000), as well as combinations between them, together with or without bathymetric data. They concluded that for a 500 m 3 /s discharge, the 4 m resolution DEM yielded inundated area differences up to 7.3 %.…”

Investigating the Role of DEM Resolution and Accuracy on Flood Inundation Mapping

“…The areas with water depth greater than zero are considered to be flooded (Merwade, 2012;Noman et al, 2001;Omer et al, 2003;Tate et al, 2002). …”

“…Resolutions of DEMs can affect the parameters and attributes derived from them and influence models associated with them (Gallant & Hutchinson, 1997;Haile & Rientjes, 2005;Omer et al, 2003). The vertical accuracy of a DEM is the probability distribution of digital elevation values measured with respect to the true value.…”