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Wayne Tschirhart, PE, PMP, CFMXP Software webinar - April 24, 2014
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Topic SummaryBackground
Model Review
Documentation review
Summary
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Background SARA began reviewing CLOMR/LOMR
applications as a FEMA delegate for itsfour-county jurisdiction in 2012.
Questions about 1D/2D and 2D modelreviews prompted development ofregional modeling and review standards.
SARA aligned the standards with software reference manuals,FEMAsAppendix C - Guidance for Riverine Flooding Analysis andMapping, USACE Engineering Manual 1110-2-1416 on RiverHydraulics, and input from experienced 2D modelers.
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Model Review
First Steps Get a copy of the software reference manual
Check the version
Open the model Missing layer files
Most common is .xptin Second most common are GIS/CAD layers
Run the model Note any runtime errors/warnings Request resubmittal if it wont run
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Model Review - 1D Network Nodes
Should be located at significantchanges in stream geometry
Spill crest elevations should beabove the adjoining 2D grid, but nottoo far, and linked to 2D
Links
Represented by a conduit withuniform cross section
Natural cross sections should betruncated at banks or limits of 1Dflow in overbanks
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Model Review - 1D Network Hydraulic Structures
Does the configuration makesense?
1D Boundary Conditions
Upstream - flow hydrograph
Steady continuous flow
Unsteady discontinuous flow Downstream - water level
Are they reasonable?
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Model Review - 2D Geometry Grid Extents
Extend beyond project to allow asolution without edge effects
Boundary elements should not be used
to restrict water from leaving thedomain
Grid Cell Settings Large enough to meet study objectives
without masking important detail Cell elevations should represent an
average of points or TIN under the cell 3 to 4 cells across major 2D flow paths Not used to remove structures or lots
from the floodplain
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Model Review - 2D Geometry Grid Orientation
Should coincide with the generalflow direction through the system
Active Areas
Not necessary if grid default is set toactive
Used to define 2D domain on aninactive default grid
Perform sanity checks - Are theybeing used selectively to avoidproblems?
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Model Review - 2D Geometry Inactive Areas
Not necessary if grid default is set toinactive
Typically used to isolate 1D networkfrom 2D domain on an active defaultgrid
Perform sanity checks - Are they beingused to mask problems?
1D/2D Interfaces Ensure they are snapped to inactive /
active area boundaries Will cause large Total Model Continuity
Error value if not snapped
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Model Review - 2D Geometry 1D/2D Connections
All nodes should be connected Connections should not stray too
far upstream/downstream
2D Head Boundaries Set anywhere flow leaves domain Are they reasonable?
2D Flow Boundaries Set anywhere water is entering the
domain Are they reasonable?
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Model Review - 2D Geometry Rainfall/Flow Areas Community FPA should specifically approve use
Will be considered a change in hydrology if FISflows change
Aerial reduction required if outlet drainage area> 10 mi2
Flow Constrictions Check input
Look for documentation
Land Use Published guidance not readily available outside
software reference manuals
Some experienced users found that 2D n-valuestend to be higher than those used for 1D models
Make sure the n-values are reasonable
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Model Review - Topography Breaklines
Add definition to terrain
Were they used correctly and do
they make sense?
Fill Areas Raise terrain to a specified
elevation
Dynamic Elevation Shapes Simulate elevation-dependent
flooding
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Model Review - Topography DTM
Must be submitted with theproject
Must cover the entire project and2D domain
Should contain sufficient detailfor the purposes of the study
Verify it reasonably reflects actualterrain at the required accuracy
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Model Review - Time Series Outputs Flow
XP Software recommends placing flowlines: Just inside each of the boundaries
Upstream and downstream of key structures,through structures
Areas of particular interest to the community
Should be aligned perpendicular to flowdirection
flows are graphed and conservation of
mass is checked
Head/Velocity Extracts elevation and velocity
information at points of interest
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Model Review - Configuration Check everything under main configuration menu
Global Data
Natural sections 2D Land use Rainfall 2D soil type
others Interface files
If used, ensure they are submitted with the model
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2D Job Control
2D model should be active
Time Step Starting points
Cell size/6 for U.S. customary units Cell size/2 for metric units
Wet/Dry Depth should be reasonable or specified by
community
Smagorinsky factor should be between 0.6 and 1.0
Model Review - Configuration
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Model Review - Results 1D model results are checked through tools under
Resultsmenu
2D model results are checked through Reporting in thelayers box
Do results make sense? Water follows channels, is deeper in channels than
overland areas, etc.
Check flow entering and leaving nodes Must match published FIS flows or the requestor has
changed the hydrology and must provide new hydrology
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Model Review - Results Check for unreasonably high velocities
Look for instability
Instability shows up as rapid variations in flow/elevationwith time
Instability at the ends of the rising and falling limbs maynot be a concern
Instability during the peak should not be present
Check results at time series output lines/points
Check f low over weirs and verify it agrees with expectedflow
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Model Review - Results Check initial conditions
Were they appropriate for the flow regime?
Check volume conservation 2D volume error should be 1%
*.tlf file, bottom
1D continuity error should be 5% Good *.out file, Table E22
Check floodplains Are they reasonable?
Check upstream & downstream boundaries Are water surface elevations within foot of the FIS profile?
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Model Review - Diagnostics Review the .tlf file
Very useful for finding data input problems and identifyinginstabilities
Open the file with a text editor and search for any WARNING,CHECK or NOTE messages
An XY: at the beginning of a line indicateswhether the error,warning, check or other message has also been redirected to a .miffile
Opening the .mif file in the main map window often providesa far more rapid way of locating warning/error messageswithin the model domain(s)
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Model Review - Diagnostics Review the .out file
A list of hydraulic tables located near top of file providesexcellent reference for sections to check for specific 1Dmodel performance and warnings/errors
Nodes with a high number of iterations should beinvestigated and may indicate a problem
Review the messages.csv file
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Documentation Review Primary reason 2D or 1D/2D model additional data letters
at FEMA review level is incomplete documentation
FEMA Appendix C Good source for documentation requirements
Alternative method justification
The study must show that the original model wasinappropriate
Inappropriate means the model was not designed to simulatethe flow regime or model assumptions were violated
Simply stating the original model was inappropriate is notsufficient
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Documentation Review Grid development Extents, cell size, and orientation
Cell size
Orientation
Time step selection
Terrain Data development Modifications through elevations shapes
Roughness parameters
Boundary conditions
Soil moisture & losses Losses should not be added if hydrology already includes them
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Documentation Review Hydraulic structures
Explain hydraulic structure representation and how theyretied to the 2D grid
List the grid cells associated with the structure (if using 2Dhydraulic structures)
Discuss the derivation technique/source methodology ofrating tables
Validate head loss calculations against model head losses
Calibrate to recorded observations or high water marks Use desktop calculations based on theory and/or standard
publications Compare results with another hydraulic software.
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Documentation Review Model Comparisons
Requirements are the same regardless of whether model is 1D, 1D/2D,or 2D
Effective vs. Duplicate Effective Duplicate Effective vs. Corrected Effective Corrected Effective vs. Existing Conditions
Existing Conditions vs. Proposed Conditions
Compare water surface elevations via tables
Compare top widths via tables
Profiles Must be submitted even if software does not produce them
All major flow paths must have a profile
Duplicate effective profile must match effective model within foot
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Documentation Review Floodways
Require pre-approval from the RPO
Floodway methodology must be documented
Errors/Warnings An explanation of all errors, warnings, and notifications
should be included
The modeler may have to open the output files and manually
search for warnings or notifications the model produces
Calibration Should be documented, even if its calibrated to an effective
model
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Workmap Review Requirements are the same as 1D with some additions
Top Widths have to match model top widths
Cross section lengths have to match model sections
Profile from map must match profile plots within 0.1 foot
2D domain coverage must be represented
Cell numbering scheme must be noted
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Summary Use the appropriate level of modeling for the flow regime
The increased complexity of a 1D/2D or 2D model calls fora much higher threshold for documentation
One-dimensional model parameters do not always crossover to multidimensional models
Communities should develop/adopt multidimensionalmodel standards as a reference framework for consistency
Software reference manuals are an awesome resource fordetermining whether model parameters are reasonable
Review is easier if you establish a consistent work f low
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SARA Regional Modeling Standards:
http://www.sara-tx.org/public_resources/library.php
Contact Info:
210-302-3678
LinkedIn @ Wayne Tschirhart
Questions/Resources
http://www.sara-tx.org/public_resources/library.phpmailto:[email protected]:[email protected]:[email protected]:[email protected]://www.sara-tx.org/public_resources/library.phphttp://www.sara-tx.org/public_resources/library.phphttp://www.sara-tx.org/public_resources/library.phphttp://www.sara-tx.org/public_resources/library.php