Processing Geospatial Data with HEC-GeoRAS 3.1

WailupeRAS Plan: Wailupefirstrun 4/24/2003 1488.741

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1053.589

WS 1000yr Ground Bank Sta 552.386 Brad Endres CVEN 689 28 April 2003

Overview • Hydrologic Review • Hydraulics Review • Applicable Software • Data Requirements • Major Functions of GeoRAS • Demonstration of Capabilities • Application to Area of Interest • Benefits and Drawbacks • Questions

Hydrologic Review • Engineering Hydrology – Occurrence, circulation, & distribution of water – Frequency & magnitude of events (flood/drought) for engineering designs Gage station Hyetograph Hydrograph

Hydraulics Review • Hydraulics – Results in design specifications for bridges, culverts, and hydraulic structures – Water Surface profile calculations based on flow data Energy Equation Example Floodplain

Hydraulics Review • Floodplain Delineation – Conventional Method of quad maps & hand calculations – Digital Method • Digital Terrain Model (DTM) in ArcView 3.2

• GeoRAS automates geometry calculations • HEC-RAS models given flow & delineates floodplain • Export back to ArcView for additional grids .004

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5 0 -5 EG 50 yr WS 50 yr Ground Bank Sta -10 -15 0 200 400 600 Station (f t) 800 1000

Applicable Software • ArcGIS w/ extensions – 3D & Spatial Analyst – HEC-GeoHMS – HEC-GeoRAS • HEC-HMS – Simulates rainfall-runoff for the watershed • HEC-RAS – Simulates water surface profile of a stream reach

Data Requirements • Triangular Irregular Network (TIN) • DEM (high resolution) – use stds2dem.exe if downloading from USGS • Land Use / Land Cover – Manning’s Coefficient • See USGS website CRWR image

Major Functions of GeoRAS • Interface between ArcView and HEC-RAS • What does it do?

– PreRAS Menu - prepares Geometry Data necessary for HEC RAS modeling – GeoRAS_Util Menu – creates a table of Manning’s n value from land use shapefile – PostRAS Menu – reads RAS import file; delineates flood plain; creates Velocity and Depth TINs

Demonstration of Capabilities • Load TIN 3-D Scene • Create Contour Lines 3-D Scene

Demonstration of Capabilities • Create Stream Centerline • Create Banks Theme • Create Flow Path Centerlines • Create Cross Section Cut Lines • Add/Create Land Use Theme • Generate RAS Import File

Demonstration of Capabilities Land Use Theme Stream Centerline Right Bank Flow Path Centerlines Cross Section Cut Lines

Demonstration of Capabilities • Generate RAS GIS import file • Open HEC-RAS and import RAS GIS file • Complete Geometry, Hydraulic, & Flow Data • Run Analysis • Generate RAS Export file

Demonstration of Capabilities • RAS GIS import file:

Demonstration of Capabilities • RAS GIS export file:

Demonstration of Capabilities • New GIS data • PostRAS features – Water Surface TIN – Floodplain Delineation – polygon & grid – Velocity TIN – Velocity Grid

Demonstration of Capabilities • Floodplain Delineation (3-D Scene)

Demonstration of Capabilities Depth Grid (Darker = Deeper) Velocity Grid (Darker = Faster)

Application to Area of Interest • Background on Bolinas Lagoon, CA USACE Map USGS Map

Application to Area of Interest • Bolinas Lagoon, CA USACE Image USACE Image

Application to Area of Interest • Employing ArcView, GeoRAS, and RAS for Main Channel Depth Analysis (1968) PreRAS PostRAS 13.5 ft

Application to Area of Interest • Employing ArcView, GeoRAS, and RAS for Main Channel Depth Analysis (1988) PreRAS PostRAS 21.0 ft

Application to Area of Interest • Analysis of Results – Sensitivity to stream centerline placement – Accuracy improves with more XS cut lines – XS cut lines hard to draw on meandering stream – Possible deepening of the main channel over time – Analysis of area complicated by tidal flows – Validate findings • FEMA floodplain maps • USACE studies Bolinas watershed

Benefits & Drawbacks • Overall Benefits – Elevation data is more accurate with TIN files • Better representation of channel bottom – Rapid preparation of geometry data (point and click) • Precision of GIS data increases precision of geometry data – Efficient data transport via import/export files – Velocity grid – Depth grid Bolinas Lagoon on 10m DEM

Benefits & Drawbacks • Overall Benefits – Floodplain maps can be made faster – Floodplain maps can include several flow scenarios – HEC-RAS allows steady & unsteady flow analysis – GIS tools aide engineering analysis • Automated calculation of functions (Energy Equation) • Structural validation of hydraulic control features • Voluminous data on World Wide Web – Makes data into visual event – easier for your brain to process!

More GIS!

Benefits & Drawbacks • Overall Drawbacks – Time required to learn several software packages – Availability of TIN or high resolution data – Estimation of Manning’s Coefficient • Few LU/LC files have this as attribute data – Creating XS cut lines demands attention to detail – Velocity distribution data may not be calculated • HEC-RAS export file without velocity data means no velocity TIN or grid

Questions • What are your questions?

New 3-D Viewer in HEC-RAS 3.1