Terrain Data
[Page Summary]
“The USDOI in its report Inundation Mapping/Modeling Subproject Report, Implementation Phase 1: Launch Risk Reduction, dated March 2011, recommends that as a general rule, larger dam breach flows, in terms of peak breach discharge and volume, do not require as detailed terrain data as would smaller flows. Smaller flood flow requires a more detailed definition of drainage paths, which creates a need for more accurate terrain data.
“Before performing an inundation study, available terrain sources should be carefully evaluated to identify the best-available data by considering numerous factors, including date, accuracy, and spatial extent of data to name a few. For instance, the selection of the level of detail and accuracy of the terrain data to be used for a dam breach study should consider the level of detail of the hydrologic and hydraulic modeling used for the study. A tier 1 simple and basic study, described in section 6.3 of this guidance document, covering a rural area does not warrant the same level of detailed terrain data as tier 2 intermediate or tier 3 advanced studies for heavily populated areas. Section 9 provides further discussion on terrain data and cross-section accuracy for use in dam breach studies.
“To achieve a suitable level of accuracy, it may be necessary to combine multiple terrain datasets to ensure that either the best available or an acceptable accuracy terrain data source is utilized throughout the spatial extent of the inundation. When combining terrain datasets, edge matching must be carefully reviewed to ensure that no artificial walls or drops are inadvertently created during the merge. Combined datasets must also use consistent horizontal and vertical datum and units” [1].
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Revision ID: 2714
Revision Date: 09/11/2022