floodplain mapping using av-ras
DESCRIPTION
Floodplain Mapping Using AV-RAS. Esteban Azagra and Francisco Olivera, Ph.D. Center for Research in Water Resources University of Texas at Austin. Objective. AV-RAS is a system of ArcView tools developed in Avenue -- the ArcView programming language -- that: - PowerPoint PPT PresentationTRANSCRIPT
Floodplain Mapping Using AV-RAS
Esteban Azagra and Francisco Olivera, Ph.D.Center for Research in Water Resources
University of Texas at Austin
Objective
• AV-RAS is a system of ArcView tools developed in Avenue -- the ArcView programming language -- that:
• extracts hydrologic data from digital terrain data, and
• maps the HEC-RAS results back on the digital spatial data
Floodplain Mapping Approach
CRWR-PrePro AVRasWatersurfaceprofiles
ArcView
Geometricdata
ParametersSchematic
Flowdischarge
HEC-HMS HEC-RAS
Digital Spatial Data
ArcView
HEC-RASHEC-HMS
• Digital spatial data required:
• Digital elevation model (DEM).
• Vector stream network.
• Land use / land cover
• Soils
Streams and Watersheds
ArcView
HEC-RASHEC-HMS
• CRWR-PrePro is used for:
• Stream and watershed delineation.
• Determination of stream and watershed hydrologic parameters.
HEC-HMS: Flow Determination
ArcView
HEC-RASHEC-HMS
HMS-RAS ConnectionHMS Junctions RAS Cross-sections
ArcView
HEC-RASHEC-HMS
HMS-RAS Connection
ArcView
HEC-RASHEC-HMS
(0500, 3559.6)
HMS Hydrograph
RAS Flow Data
Digital Terrain Model: TIN
ArcView
HEC-RASHEC-HMS
• Observed points and breaklines for constructing a triangular irregular network (TIN).
•TIN components:- nodes- edges- triangles
Digital Terrain Model: TIN
ArcView
HEC-RASHEC-HMS
• 3D display of a TIN.
Digital Terrain Model: TIN
ArcView
HEC-RASHEC-HMS
Digital Terrain Model: TIN
• Embedding Buildings into the TIN.
ArcView
HEC-RASHEC-HMS
Cross Sections
• Stream centerline.• Banks.• Flow paths.• Cross sections.
ArcView
HEC-RASHEC-HMS
• Bridges are not captured by the TIN: cross sections should NOT be defined at the bridges.
ArcView
HEC-RASHEC-HMS
Cross Sections
Hydraulic Modeling with RAS
• RAS stream geometry.
• Cross-sections extracted from the TIN.
ArcView
HEC-RASHEC-HMS
Hydraulic Modeling with RAS
• Water surface elevations.
ArcView
HEC-RASHEC-HMS
Floodplain Mapping
ArcView
HEC-RASHEC-HMS
• Floodplain for 500 cfs.
Floodplain Mapping
• 2-D floodplain animation (500 – 5,000 cfs).
Floodplain Mapping
• 2-D representation of the Central Park detention pond.
Floodplain Mapping
• 3-D floodplain animation.
Limitations
• Bridge and culvert data has to be entered by hand.
CS 9658
490
495
500
505
510
515
520
525
0 20 40 60 80 100 120 140 160
Distance along cross-section (ft)
Ele
vati
on a
bov
e M
LS
(ft
)
Field data
Data extracted from the TIN
Limitations
• The accuracy obtained from TIN data might not be good enough.
Solutions
Source: digital representation of NYCgenerated by ASI and published by ESRI.
• New technologies (i.e. LADAR) are improving the quality of the digital terrain representations.
Source: digital representation of NYCgenerated by ASI and published by ESRI.
Solutions
• New technologies (i.e. LADAR) are improving the quality of the digital terrain representations.
Conclusions
• Automation of floodplain delineation results in time and resource savings.
• The lack of subjectivity provides standardized results.
• Applications include:• Design of control structures (detention
ponds, culverts, bridges, …).• Flood insurance rate determination.• Real-time flood emergency mapping.
• The accuracy of the digital terrain model has to be improved.
• Some field data will be still required.