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Floating Away: Connecting AutoCAD® Civil 3D® with HEC-RAS for Floodplain Mapping - CI4043Andy Carter, PEProject Manager – Halff Associates, Inc – Austin, TX

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Class Summary

In this class you will explore extracting detailed hydraulic floodplain models from a LiDAR terrain and perform quick and accurate floodplain delineations on AutoCAD®

Civil 3D ® surfaces by interacting with RAS Mapper in Hydrologic Engineering Centers River Analysis System (HEC-RAS) version 4.1.0 from the U.S. Army Corps of Engineers.

This class will further explore the use of grading objects for developing quick and iterative floodplain analysis to determine the comparative impacts of proposed grading in the floodplain.

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Before we begin….

We are a big class… so Please hold all questions and comments until the end of the lecture.

Silence your phones now!!

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Learning Objectives

At the end of this class, you will be able to: Develop an existing and proposed HEC-RAS hydraulic model from a LiDAR surface

Use Civil 3D® surfaces with HEC-RAS Mapper to create accurate floodplain delineations

Connect HEC-RAS and Civil 3D® as a full floodplain mapping solution

Use grading objects to create quick and accurate floodplain reclamation analysis

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Programs Utilized in this Tutorial

AutoCAD ® Civil 3D ® 2012

HEC-RAS v4.1.0 – a free and publicly available software. (http://www.hec.usace.army.mil/)

SAGA (System for Automated Geoscientific Automation) – an open source GIS platform available for download (http://sourceforge.net/projects/saga-gis/files/)

Civil3D HEC-RAS Flipper (A small program written specifically for this tutorial and available at the class website)

RASgeoToCAD2011.dvb (An AutoCAD ® VBA that assists with creating a “Water Surface” from files exported from HEC-RAS available from class website)

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Eight is enoughStep 1: Building an Existing Ground Terrain Model from

LiDAR

Step 2: Export a HEC-RAS Model

Step 3: Creating a Hydraulic Model in HEC-RAS

Step 4: Export surface from Civil3D, convert and use HEC-RAS Mapper to delineate the floodplain.

Step 5: Delineating a Floodplain in RAS Mapper

Step 6: Import the floodplain to Civil 3D®

Step 7: Creating a Floodplain Surface

Step 8: Developing a proposed grading plan for a Post-Project HEC-RAS model

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1) Building an Existing Ground Terrain Model from LiDAR

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Raw Point LiDAR point cloud

Sample only the ground

Create an Existing Ground Surface

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2) Export a HEC-RAS Model

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With a surface, alignment and sample lines…

…Export a GEO file to HEC-RAS

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Not so fast my friend! We have some flipping to do…

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4) Export surface from AutoCAD® Civil3D® and convert to FLT for use with HEC-RAS Mapper to delineate the floodplain..

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Export a DEM from AutoCAD ® Civil 3D ®Convert DEM to FLT with SAGA GIS

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HEC-RAS Mapper is picky… Clean up the header (HDR) file of SAGA’s FLT

From this… …to this

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5) Delineating a Floodplain in RAS Mapper

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Delineate on the FLT

RAS Mapper creates a floodplain SHP file

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6) Import the floodplain to AutoCAD® Civil 3D®

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Use “mapimport” and bring in the floodplain shapefile

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7) Creating a Floodplain Surface

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HEC-RAS now outputs Geometry as GML and Output as XML …

GML

XML

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With a custom AutoCAD® VBA, use the XML and GML to construct a water surface

Using the Cross Sections elevated to the floodplain elevation as breaklines and the floodplain limits as a boundary, create a “water surface”.

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8) Developing a proposed grading plan for a Post-Project HEC-RAS model

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Using the “Water Surface” + freeboard, create a feature line of the proposed reclamation limits.

Use slope and infill grading objects to create a proposed regrading surface. Paste the proposed surface to the existing ground and run delineation procedures similar to the existing conditions model. (Steps 1 thru 7)

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Goal 1: A Pre- and Post project HEC-RAS model that reflects the proposed grading

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Goal 2: AutoCAD data to be used in producing hydraulic workmaps.

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Autodesk, AutoCAD* [*if/when mentioned in the pertinent material, followed by an alphabetical list of all other trademarks mentioned in the material] are registered trademarks or trademarks of Autodesk, Inc., and/or its subsidiaries and/or affiliates in the USA and/or other countries. All other brand names, product names, or trademarks belong to their respective holders. Autodesk reserves the right to alter product and services offerings, and specifications and pricing at any time without notice, and is not responsible for typographical or graphical errors that may appear in this document. © 2011 Autodesk, Inc. All rights reserved.