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 operations 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.