Floodplain Mapping using TINs

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Triangulated Irregular Networks (TINs)

• Representation of stream channels using TINs • Floodplain delineation using HEC-HMS, HEC-RAS and ArcView

TIN with Surface Features Classroom UT Football Stadium Waller Creek

A Portion of the TIN

Input Data for this Portion Mass Points Soft Breaklines Hard Breaklines

TIN Vertices and Triangles

TIN Surface Model Waller Creek Street and Bridge

3-D Scene

3-D Scene with Buildings

Floodplain Mapping using TINs

• • Triangulated Irregular Networks (TINs)

Representation of stream channels using TINs

• Floodplain delineation using HEC-HMS, HEC-RAS and ArcView

River Modeling 

River hydraulic modeling provides a tool to study and gain understanding of hydraulic flow phenomena

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Topographic data describe the geometry of the simulated river system and permit the establishment of model topology

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HEC-RAS, MIKE 11 all hydraulic models require channel information for model development

River Morphology

Flood Inundation

Floodplain Delineation

Floodplain Delineation

Channel and Cross-Section Direction of Flow Channel Cross-Section

ProfileLines

Types

1- Thalweg 2- LeftBank 3- RightBank 4- LeftFloodLine 5- RightFloodLine

ProfileLines and CrossSections are linked through Channel_ID

TIN as a source of cross-sections

CrossSections

Floodplain Mapping using TINs

• • Triangulated Irregular Networks (TINs) • Representation of stream channels using TINs

Floodplain delineation using HEC-HMS, HEC-RAS and ArcView

Floodplain Mapping Approach HEC-HMS HEC-RAS

Flow discharge

HEC-GeoHMS

Parameters Schematic Geometric data

HEC-GeoRas

Water surface profiles

ArcView

Purpose • Integrate/Validate existing tools for floodplain determination and visualization.

– Reduce the dependence on field data .

– Improve the floodplain analyses capabilities (lower costs and more accuracy).

Digital Spatial Data • Digital elevation model (DEM).

• Stream definition.

HEC-HMS HEC-RAS ArcView

CRWR-PrePro • Watershed delineation.

• Reach/Watershed parameters determination.

HEC-HMS HEC-RAS ArcView

HEC-HMS: Flow Determination

HEC-HMS HEC-RAS ArcView

HMS-RAS Connection HMS Junctions RAS Cross-sections

HEC-HMS HEC-RAS ArcView

HMS-RAS Connection HMS Hydrograph RAS Flow Data (0500, 3559.6)

HEC-HMS HEC-RAS ArcView

Digital Terrain Model: TIN • Observed points and breaklines for constructing a triangular irregular network (TIN).

HEC-HMS HEC-RAS ArcView

Digital Terrain Model: TIN • Embedding Buildings into the TIN.

HEC-HMS HEC-RAS ArcView

GIS-RAS Connection • Stream centerline.

• Banks.

• Flow paths.

• Cross sections.

HEC-HMS HEC-RAS ArcView

GIS-RAS Connection • Location of cross sections.

HEC-HMS HEC-RAS ArcView

Hydraulic Modeling with HEC-RAS • RAS stream geometry.

• Cross-section extracted from the TIN.

HEC-HMS HEC-RAS ArcView

Hydraulic Modeling with HEC-RAS • Resulting water elevations.

HEC-HMS HEC-RAS ArcView

Floodplain Mapping • Floodplain for 500 cfs.

HEC-HMS HEC-RAS ArcView

Floodplain Mapping • 2-D floodplain animation (500 – 5,000 cfs).

Floodplain Mapping • 3-D floodplain animation.

• Bridges/culverts: - depend on field data.

- data input by hand.

Limitations

• The accuracy obtained from our TIN is not good enough.

Limitations

• New technologies (i.e. LADAR) are improving the quality of the digital terrain representations.

Solutions

Source: digital representation of NYC generated by ASI and published by ESRI.

Michael Schultz NWS River Forecast Center Fort Worth, Texas 1998 Guadalupe Flood

Cross-Sections developed using HEC-GeoRAS and National Elevation Dataset

Hydrologic simulation Using NWS Fldwav model