computer science

HEC-HMS

HEC-HMS is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand HEC-HMS rather than just read about it. In short: The HEC-HMS (Hydrologic Engineering Center - Hydrologic Modeling System) is a hydrology software of the U.S. Army Corps of Engineers.

Key takeaways

HEC-HMS belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HEC-HMS to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HEC-HMS from memory before moving on to harder problems.

Reference excerpt

The HEC-HMS (Hydrologic Engineering Center - Hydrologic Modeling System) is a hydrology software of the U.S. Army Corps of Engineers. It is designed to simulate the precipitation-runoff processes of dendritic drainage basins. It is designed to be applicable in a wide range of geographic areas for solving the widest possible range of problems. This includes large river basin water supply and flood hydrology, and small urban or natural watershed runoff. Hydrographs produced by the program are used directly or in conjunction with other software for studies of water availability, urban drainage, flow forecasting, future urbanization impact, reservoir spillway design, flood damage reduction, floodplain regulation, and systems operation. The program is a generalized modeling system capable of representing many different watersheds. A model of the watershed is constructed by separating the water cycle into manageable pieces and constructing boundaries around the watershed of interest. Any mass or energy flux in the cycle can then be represented with a mathematical model. In most cases, several model choices are available for representing each flux. Each mathematical model included in the program is suitable in different environments and under different conditions. Making the correct choice requires knowledge of the watershed, the goals of the hydrologic study, and engineering judgement. HEC-HMS was developed beginning in 1992 as a replacement for HEC-1 which has long been considered a standard for hydrologic simulation. It was written in the FORTRAN language and until 1984 could only be run on a mainframe computer. When desktop computers became popular the program was ported to the PC. The new HEC-HMS provides almost all of the same simulation capabilities, but has modernized them with advances in numerical analysis that take advantage of the significantly faster desktop computers available today. It also includes a number of features that were not included in HEC-1, such as continuous simulation and grid cell surface hydrology. It also provides a graphical user interface to make it easier to use the software. The program is now widely used and accepted for many official purposes, such as floodway determinations for the Federal Emergency Management Agency in the United States.

Illustrations

Worked examples

Example 1 — a first encounter with HEC-HMS

Start with the simplest possible case. Write down what HEC-HMS claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to HEC-HMS before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about HEC-HMS ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of HEC-HMS

In research: HEC-HMS appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses HEC-HMS in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: HEC-HMS is common in secondary-school and first-year university syllabi. It links to neighbouring topics Hydrology software, so understanding it makes those chapters shorter.
In everyday life: Look for HEC-HMS outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study HEC-HMS in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HEC-HMS means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain HEC-HMS out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HEC-HMS in simple terms?

The HEC-HMS (Hydrologic Engineering Center - Hydrologic Modeling System) is a hydrology software of the U.S. Army Corps of Engineers.

Why does HEC-HMS matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study HEC-HMS?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on HEC-HMS.