Using GIS to Build Hydraulic Models Faster


Courtesy of Innovyze

The use of hydraulic models, already widespread, continues to grow rapidly.  Modeling is used increasingly all around the world to address planning and operational issues in water supply networks, collection systems, and river management.

Much of this growth results from the rapid advances in the capabilities of the best of the hydraulic modeling software solutions, which constantly improve the cost/benefit balance of modeling.  These advances fall into three general categories.  First, the functional scope of modeling software increases constantly – specific features in the software may automate many time-consuming tasks, such as evaluating fire flow capabilities, or carrying out analyses of the risks of sewer overflows. Second, some modeling software now handles very big networks, so that collection system networks of 100,000 pipes can be modeled in full with acceptable run times.  And third, the best modeling software makes models ever quicker and easier to build and use.

This third factor, ease of use, requires two components.  One is an intuitive and effective user interface.  The other is integration with the external data sources that are commonly used in hydraulic engineering.  Perhaps the commonest of these is GIS - the ability to build and update models from GIS, and export data back to the GIS, is a key attribute of a good modeling package.

Sasa Tomic is Senior Vice President at Wallingford Software, producer of data management and network modeling software for the water industry, including the InfoWorks modeling suite.  He explained some of the specifics required of GIS/model integration.  “There are thousands of InfoWorks hydraulic models around the world, many of which are linked to ArcGIS.  All GIS users can greatly leverage the value of their data by using it to build models quickly.

“However, these links require more than the wholesale import of raw GIS data into a model.  To deliver maximum value, the model needs additional functionality to manage GIS data import and export. An example of the complexity of moving data from a GIS into a model occurs when the assets in a model do not map one-to-one with the assets in the GIS – there is often a one-to-many relationship for assets such as valves or pumps.  To automate model updates from GIS, InfoWorks maintains the map of IDs for each element – one for the model, and one for GIS.

“Another feature of GIS integration we offer is the ability to interrogate a GIS database, asset management database, and hydraulic simulation results in a single environment. It is very useful for the user to query and edit GIS data, modeling network and asset database in a single view. GIS and asset data can be used to automatically create or update models and model results can be used to validate and update asset database or GIS.  For example, being able to answer the query ‘Show all hospitals where the pressure difference between Model Run 1 and Model Run 2 is greater than X.’ is a very useful capability.”

These facets of GIS/model integration are also valued by modeling practitioners.  Helen Lu of Hazen and Sawyer has four years experience of sewer modeling, using many of the available modeling softwares, working on the New York City sewer system among other projects.  She said “Hazen and Sawyer is very well known for its extensive expertise in both hydraulic modeling and GIS.  Modeling systems that have good links with GIS are highly beneficial for us.  When I say good links, I look for example for data exchange flexibility.  Being able to import additional information, such as text, from GIS into a model is very useful, as are scripts to help trim the GIS data into the subsets needed for the model.  Another feature I find useful is flagging the data source on import to the model, which helps me to assess the data quality.

“A key factor in the import of GIS data is the ability of the model to process it.  GIS data such as street data or aerial photography is often used as background display for a model, resulting in large amounts of data.  For example, I have worked with a 32,000 pipe network, with a big street layer shape file as background.  That is only manageable if the modeling software has the power to handle big data sets.

“Once digital terrain models are imported, it is useful if the model can use it first to infer missing model parameters, and then to create a ground model that will, in sewer modeling for example, provide an easy way to visualize the subcatchment surface, manhole flooding, and underground sewer layout in 3D view.  For water modeling, I may want to define the pressure boundaries based on the pressure zone GIS polygon, and check the result with a boundary tracing tool.  In my view GIS-model integration will be the trend in models in the future, and InfoWorks, which offers already all the features I have mentioned, exemplifies this.”

Rajan Ray shares these views on the importance of powerful GIS/model integration. He is Services Director with IDModeling, a specialty service company delivering hydraulic modeling solutions for both water/wastewater utilities and engineering consulting firms. IDModeling focuses on hydraulic model construction, GIS-integration, calibration, analyses, and software or system-specific training.  He gave further examples of the snags of GIS data import that modeling software needs to address “The first step in building a hydraulic model is often the integration between the modeling software and the GIS database.  However, raw GIS asset data often has to be adjusted in order to perform hydraulic calculations. For example, obsolete pipes or house connections need to be removed or GIS named domains for pipe materials need to be mapped to the modeling software material codes.  Although this is a simple task in GIS, it often prevents the automated updates of the model from GIS.  The solution is to have pre-processing integrated with the import process.

“Another desirable feature is the automatic correction of common errors when data is imported or updated. Again, this requires the model to remember the specific procedures for the next model update, so that the import routine can become automatic. All these features are within InfoWorks, boosting the productivity of model builders.”

To sum up, users of ESRI and other GIS systems for hydraulic engineering already have much of the data required for modeling.  With good modeling software, much of the build process can be largely automated from GIS data.  Given the right modeling software, every GIS user now has a valuable opportunity to leverage the value of their GIS investment by using it to develop hydraulic models.

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