The Waterfall methodology—also known as the Waterfall model—is a sequential development process that flows like a waterfall through all phases of a project (analysis, design, development, and testing, for example), with each phase completely wrapping up before the next phase begins.
It is said that the Waterfall methodology follows the adage to “measure twice, cut once.” The success of the Waterfall method depends on the amount and quality of the work done on the front end, documenting everything in advance, including the user interface, user stories, and all the features’ variations and outcomes. With the majority of the research done upfront, estimates of the time needed for each requirement are more accurate, and this can provide a more predictable release date. With a Waterfall project, if parameters change along the way, it’s harder to change course than it is with Agile methodology.
Advantages of the Waterfall methodology
The Waterfall methodology is a straightforward, well-defined project management methodology with a proven track record. Since the requirements are clearly laid out from the beginning, each contributor knows what must be done when, and they can effectively plan their time for the duration of the project.
Other benefits of the Waterfall method include:
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Developers can catch design errors during the analysis and design stages, helping them to avoid writing faulty code during the implementation phase.
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The total cost of the project can be accurately estimated, as can the timeline, after the requirements have been defined.
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With the structured approach, it is easier to measure progress according to clearly defined milestones.
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Developers who join the project in progress can easily get up to speed because everything they need to know should be in the requirements document.
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Customers aren’t always adding new requirements to the project, delaying production.
Disadvantages of the Waterfall methodology
Like any development process, the strengths in one area might mean weaknesses in the other. The Waterfall methodology’s insistence on upfront project planning and commitment to a certain defined progress means that it is less flexible, or agile, later in the game. Changes that come further in the process can be time-consuming, painful, and costly.
Other reasons the Waterfall methodology may not work include:
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Projects can take longer to deliver with this chronological approach than with an iterative one, such as the Agile method.
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Clients often don’t fully know what they want at the front end, opening the door to requests for changes and new features later in the process when they’re harder to accommodate.
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Clients are not involved in the design and implementation stages.
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Deadline creep—when one phase in the process is delayed, all the other phases are delayed.
Who uses the Waterfall model?
The Waterfall process is adopted by project managers who are faced with development projects that:
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Don’t have ambiguous requirements.
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Offer a clear picture of how things will proceed from the outset.
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Have clients who seem unlikely to change the scope of the project once it is underway.
If a project manager prefers clearly defined processes, where cost, design, and time requirements are known upfront, then the Waterfall method is the way to go, as long as the project itself is conducive to those constraints.