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Published byΚύνθια Τομαραίοι Modified over 5 years ago
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Automated Techniques for Hydraulic Modeling Applications
David Knipe Engineering Section Manager
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Presentation Outline Basics of Hydraulic Modeling
Using the new local resolution NHD data in modeling Using DEM or TIN topography to derive cross section points Deriving hydraulic modeling parameters Post processing of hydraulic modeling
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IDNR modeling efforts Zone A modeling First Order Approximations
Geo – Sub Divided Area Rating
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Basics of Hydraulic Modeling
Compute flood elevations Determine floodway Determine impact of projects Bridge / Culvert modeling
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HEC-RAS USACE modeling program / Hydrologic Engineering Center
Industry standard 1-d hydraulic modeling
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Manning’s equation Q – peak discharge (cfs)
N – manning’s n (roughness) A – Area R – Hydraulic Radius (Area / Wetted Perimeter) S – Slope of energy grade line (approximate by stream slope)
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Manning’s equation
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Manning’s equation
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Geometric Setup for HEC-RAS
Stream Centerlines Cross Sections Bridge / Culvert modeling
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Local Res NHD Under development Stream centerlines at 1:2400 or better
Much more dense than 24K NHD
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Line directionality
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Stream centerline Need to extract centerline from the NHD
Directionality of line is important
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Cross section stationing
Use Tokens and “Polyline” commands to compute stationing CrossSections = [] for row in arcpy.da.SearchCursor(“S_XS.shp", CrossSections.append(row[0]) for x in CrossSections: pt1 = StreamCenterline.intersect(x, 1).centroid sta = int(StreamCenterline.measureOnLine(pt1))
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DEM / TIN High quality DEM’s are important (30M DEM will not cut it)
May need to enhance with below water information Will need 3D analyst to do most functions
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Interpolate Shape Need (Station, Elevation) for RAS
Use “InterpolateShape_3d” to create 3D layer Use Linear Referencing tools to create M – or use Polyline measurement tools
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Cross Sections in RAS Extend sections farther than normal
500 point limit – need to filter Can write “sdf” file to import into RAS
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Manning’s N Relating Manning’s N To NLCD dataset
Table from “Web Based implementation of Fast Dam Break Flood Modeling Capabilities (Altinakar, et al) (2011)”
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Manning’s N
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Channel Bank Stations Defines channel from left & right overbank
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Channel Bank Stations Robinson, B.A., 2013, Regional bankfull-channel dimensions of non-urban wadeable streams in Indiana: U.S. Geological Survey, Scientific Investigations Report 2013–5078, 33 p., available only at
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Post processing Floodplain delineations Depth Grids
Depth grids are a Risk MAP non regulatory product, but are easy to produce.
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Post processing Need to remove artifacts
Smooth out boundary using “Bend Simplfy”
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Automated Techniques for Hydraulic Modeling Applications
David Knipe Engineering Section Manager
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