xpsolutions 1d-2d review

8/12/2019 XPSolutions 1D-2D Review

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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:

[email protected]

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

xpsolutions 1d-2d review

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