Source: Innovyze Support Portal

Introduction

This article shows how the single valued critical flow of the rational method has been implemented in XP-SWMM. Historically storm water design has been accomplished using the Rational method ensuring that each segment of the system can carry the flow of a return period that matches the time of concentration to that point. Using this method allowed a simple spreadsheet or tabular implementation but it is unable to take in to account storage effects of conduits and ponds etc. …


source: Innovyze Support Portal

A common model building task is importing CAD files into XPSWMM.

Import CAD files is a little different from importing other type of external files. It starts with loading the CAD file as a background.

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source: Innovyze Support Portal

XPTable is very powerful, it can expose almost all of the model parameters, attributes and results in a tabular format. However, from time to time, figuring out where to find the field when building an XPTable can be tricky. Here are a few quick tips.

  1. You can create a table with all the variables into a table, the header will be grouped. If you can identify the value in the table, using the header information you will be able to find the variable.
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2. Hovering your mouse over the text box in the user interface, it will show the variable name in the tooltip


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Delineating subcatchment to most people is not a particularly interesting task. But from time to time, it can be fun. Yesterday I got a call from a customer asking how to import a subcatchment that looks like a donut into the model.

My first reaction was what on earth is this thing? Why does it have a hole?

Eventually I talked to the customer, the time she opened the model, I knew the answer.

It is a treatment plant! Now I remembered the storm water project I did a long time ago for the same plant. For the facilities that process sludge, it needs to have a buffer so that all the storm water from these buffer where sludge can spill drains to the sanitary sewer instead, and that’s why we need these holes in the subcatchments. …


source: Innovyze Support Portal

What is model instability?

Due to the explicit nature of the numerical methods used for Dynamic Wave routing (and to a lesser extent, Kinematic Wave routing), the flows in some links or water depths at some nodes may fluctuate or oscillate significantly at certain periods of time as a result of numerical instabilities in the solution method. SWMM does not automatically identify when such conditions exist, so it is up to the user to verify the numerical stability of the model and to determine if the simulation results are valid for the modeling objectives (Chapter 8.4 of EPA SWMM User Manual).

Time series plots at key locations in the network can help identify such situations as can a scatter plot between a link’s flow and the corresponding water depth at its upstream node. Numerical instabilities can occur over short durations and may not be apparent when time series are plotted with a long-time interval. …


source: Innovyze Support Portal

Calculating the storage volume from a storage curve turned out to be not so straight forward, most people will not remember the Frustum formulas after high school.

XPSWMM reports the storage volume at each storage curve point in the 1D report.

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It is under table E4 with the title “Variable storage data for node” for each storage node.


source: Innoyvze Support Portal

Sometimes the default display setting for XPSWMM can get messed up with 0 size symbols. As a results, after a new node is created, it can disappear.

To fix this issue, we need to reset the node display properties. The easiest way is to “restore Default”.

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Similarly, we can restore the settings for links.


source: Innovyze Support Portal

Present modeling results in maps with symbols and labels is an important task for any modeling projects.

For large models and professional quality figures with unique branding and looks, exporting the modeling results into a GIS package will be needed for the finer touches.

However, for small projects and a quick check of the modeling results, the overhead of exporting results to GIS is simply too high and XPSWMM has all the tools you’ll need to style the map and label the maps with just a few clicks.

To change the symbols of nodes and links, we’ll use the graphical encoding tool, and for advanced labeling, we’ll use the spatial report tool. …


Source: Innovyze Support Portal

For the majority of XPSWMM models, we should no longer use the interface files when generating runoff from rainfall and then route the flow through pipes. It was a feature that was used in the swmm3, swwm4 era when computer was not powerful enough (see this article for more details.). The support for interface files is mostly for backward compatibility, and should be avoided when updating an old model or setup new models.

Below are the procedures to remove interface files and run the runoff and hydraulics mode simultaneously.

Step 1 Remove the references to interface files

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Step 2 Solve Runoff & Hydraulics Mode Simultaneously


source: Innovyze Support Portal

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The flow overtopping a roadway is modeled as a weir in XPSWMM. The corresponding parameters are shown below.

  • weir length: the section of road where flow will overtop
  • weir crown: it is the max WSEL for the bridge, it should be set high enough so that no orifice flow will occur, refer to help for more information.
  • weir coefficient: a constant can be entered, or XPSWMM can use the FWHA chart to determine.

About

Mel Meng

Empowering Water Experts

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