Elevation Surface Generation for HEC-RAS Modeling Jason Gibbons - - PowerPoint PPT Presentation

Elevation Surface Generation for HEC-RAS Modeling

Jason Gibbons Anderson Perry Natural Resource Tech/GIS Tech

GEKELER SLOUGH

• Surface Water Management Plan (SWMP)

Project Overview

– Located in Grande Ronde Valley, Union County, Oregon – SWMP – Gekeler Slough

• City of La Grande
• Union County

– Focus of SWMP

• Evaluate possible improvements to address:

– Water quality issues – Water quantity issues

PROJECT LOCATION

PROJECT LOCATION

PROJECT STATISTICS

• Study Area:

– Approximately 18,000 Acres

• Gekeler Slough and Associated Tributaries:

– ±11.8 miles – 68 Channel Structures (e.g., culverts, bridges)

• Most efficient and cost-effective way to

perform analysis?

ANALYSIS SOLUTION

• USACE HEC-RAS Software and ArcGIS

Software

– LiDAR data to produce surface in ArcGIS – Import surface elevation data into HEC-RAS – Perform HEC-RAS analysis – Export results to ArcGIS

• Perform analysis to produce visual reference

guides

PROCESS

Source: USACE HEC-GeoRAS GIS Tools for Support of HEC-RAS using ArcGIS User’s Manual. Version 4.3.93. Feb., 2011

SURFACE GENERATION

• Mosaicked LiDAR

DEMs, procured from DOGAMI, to produce new surface in ArcGIS

– Entailed geoprocessing

• perations for projection

transformations and vertical elevation conversion to correspond to NGVD 29 elevations

DEM INPUTS

TRANSFORMATIONS

• DOGAMI LIDAR data for the study area were delivered in the following

geographic coordinate systems and units:

– Oregon Geographic Information Council High Accuracy Reference Network (HARN) Projection: Oregon Statewide Lambert Conformal Conic – Horizontal Datum: North American Datum 1983 (NAD 83) HARN – Vertical Datum: North American Vertical Datum of 1988 (NAVD 88) – Units: International Feet

• One LiDAR dataset is the exception to this, which was delivered in the following

coordinate system and units:

– Projection: UTM Zone 11 – Horizontal Datum: NAD 83 HARN – Vertical Datum: NAVD 88 – Units: Meters

• The Project Raster Tool was used to project the LiDAR DEMs into:

– Projection: Oregon State Plane North Lambert Conformal Conic – Horizontal Datum: NAD 83 – Vertical Datum: NAVD 88 – Units: International Feet

SURFACE GENERATION: MODEL BUILDER

FINAL SURFACE - DEM

File size: 1.09 GB

FINAL SURFACE - TIN

File size: 393 MB

CONCLUSION

• Integration of HEC-RAS and ArcGIS software packages provided the following

benefits for this project:

– Efficient DEM production for large project area. – Ability to analyze data in one program and convert that data to a usable format in another. – Ability to convey specific information related to floodwater elevations and evaluating alternative improvements for the Gekeler Slough. – MAPS – Tools that enhanced communication and collaboration among project partners.