David Ramirez, P.E. Senior Hydrologist Lower Mississippi River Forecast Center Slidell, LA Real-Time Operation of HEC-RAS at the Lower Mississippi River Forecast Center USACE/NWS/USGS Annual Tri-Agency Coordination Meeting Oct. 30 – 31, 2007

Used for locations where hydrologic techniques do not work as wellUsed for locations where hydrologic techniques do not work as well –Storm surge and other tidal effects –Areas affected by backwater –Levee breaches –Off-channel storage areas –Lateral inputs/diversions –Dam breaks LMRFC Hydraulic Modeling

Hydrologic ModelingHydrologic Modeling –Continuity equation and relationship between storage in the reach and discharge at the outlet. Hydraulic ModelingHydraulic Modeling –Continuity equation and the momentum equation. –Unsteady flow routing is more physically based and is applicable to wider range of applications. Hydraulic vs. Hydrologic Modeling

Large number of existing models available from other agencies, state, and local governments.Large number of existing models available from other agencies, state, and local governments. Data format is compatible with many other software packages.Data format is compatible with many other software packages. Excellent technical support, training and user documentationExcellent technical support, training and user documentation Modeling software is continuing to be developed by HECModeling software is continuing to be developed by HEC Why HEC-RAS?

Hydrologic Engineering Center River Analysis System (HEC-RAS) One-dimensional model.One-dimensional model. Current capabilities:Current capabilities: –Subcritical & Supercritical flow –Mixed regime (transcritical flow) –Hydraulic structures, e.g. culverts, bridges, weirs, etc. –Unsteady flow analysis –Mobile Boundary Hydraulics (sediment transport) –Water Quality Modeling

Data Requirements for a Hydraulic Model Geometry data:Geometry data: –cross sections & hydraulic structures: In-channel from field surveys and over bank from LIDAR –distance between cross-sections Surface Roughness (e.g. Manning’s n)Surface Roughness (e.g. Manning’s n) Upstream and downstream boundary conditions (flow, stage, rating curves, normal depth)Upstream and downstream boundary conditions (flow, stage, rating curves, normal depth)

HEC Geo-RAS HEC Geo-RAS New model development can use GIS New model development can use GIS Geo-referenced hydraulic models can be developed using a digital terrain model created with ESRI’s ARCGIS. Geo-referenced hydraulic models can be developed using a digital terrain model created with ESRI’s ARCGIS. Using a DTM for model geometry requires less surveyed cross sectional information. (Saves time and money!) Using a DTM for model geometry requires less surveyed cross sectional information. (Saves time and money!) Geo-referenced hydraulic models can produce inundation maps Geo-referenced hydraulic models can produce inundation maps

HEC-RAS Standard Hydraulic Geometry TIN Processing Cross Sections HEC-RAS HEC-2 Cross Sections Hydrographic Survey Inundated Area Intersect Continuous WS with Land (terrain-based interpolation) ARC/INFO & ArcView River Hydraulics Model Topographic Survey Floodplain & Channel TIN Cross Sections Extraction FLOODPLAIN MAP HEC Geo-RAS

Incorporating HEC-RAS into LMRFC Operations

NWSRFSHydrologicModel StandardHydrologicExchangeFormat(SHEF) HEC-DSS (dss utilities) DSS-Vue (Python) Updated HEC-RAS Flow and Plan files HEC-RAS Model Run (PC) DSS-Vue(Python) Writes TS back to NWSRFS Data Flow NWS Forecast

Pearl River Models Upstream boundary: Discharge from Ross Barnett Dam, Jackson, MS Lateral inflows: JHMM6 - Hanging Moss Creek DLAM6 - Strong River at D’Lo OVWM6 – Whitesand Creek at Oakvale Local flows: JACM6, ROCM6, MTCM6 and CLMM6 Downstream boundary: Stage at CLMM6 NWSRFS hydrologic model NWSRFS hydrologic model FLDWAV FLDWAV HEC-RAS HEC-RAS

HEC-RAS Geometry Pearl River Basin Geometry for both FLDWAV and HEC- RAS models are identical. Geometry data provided to LMRFC courtesy of the Vicksburg District USACE

HEC-RAS/FLDWAV Comparison

Vermilion River Models Upstream boundary: Stage at BVCL1 Bayou Carencro Local flows: VRLL1, VLSL1, VSHL1, and VRPL1 Downstream boundary: Tide gage at VCPL1 at Cypremort Point in Vermilion Bay NWSRFS hydrologic model NWSRFS hydrologic model FLDWAV FLDWAV HEC-RAS HEC-RAS

HEC-RAS Geometry Vermilion River Basin HEC-RAS - geometry uses levees with storage areas. FLDWAV – levee option does not work in OFS, used “cave-in-bank” method to account for storage area represented in HEC geometry. This area is in coastal LA is very flat, tidally influenced and subject to storm surge. VLSL1 Gage Geometry data provided to LMRFC courtesy of the New Orleans District USACE

HEC-RAS/FLDWAV Comparison

Lower Ohio/Upper Miss Junction Models Upstream boundaries: CHSI2, SMLI2, BARK2 and KYDK2 observed/projected flow Local flows: CPGM7, PAHK2, CIRI2, WKLK2, NMDM7, OBOT1 and MEMT1 Downstream boundary: Normal depth DWOPER DWOPER FLDWAV (In-The-Works) FLDWAV (In-The-Works) HEC-RAS HEC-RAS

HEC-RAS Geometry Lower Ohio/Upper Miss Junction Geometry data provided to LMRFC courtesy of the Louisville District USACE Geometry for both DWOPER and HEC- RAS models are identical. Runs as “Proof of Concept” and is not calibrated or used operationally. DWOPER is the current operational model at the LMRFC

Pascagoula River Model Under Development NWSRFS hydrologic model NWSRFS hydrologic model FLDWAV FLDWAV HEC-RAS HEC-RAS Upstream boundaries: WGAM6, MRRM6, AGRM6, BCDA1, VESM6 Local flows: PGFM6, ORAM6 from NWSRFS Downstream boundary: Tide gage

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