What is the Waterfall Methodology | Process, Advantages and Disadvantages

What is Waterfall Methodology?

Waterfall methodology is designated as a traditional project management method. Among the various existing methodologies, this is the most frequently used method. As the name suggests, the cascade approach follows the logic of a waterfall. Once the water has descended the side of the mountain, it cannot go up again, but only continue its way. Thus, as soon as a stage of the project is finished, the team moves on to the next stage; there is no (or little) backtracking. The idea is to progress naturally, step by step, until reaching the final objective by following a clear and precise direction.

The waterfall methodology comes from heavy industries such as automotive or building. The first description of this approach appears in an article by Winston Royce published in 1970. Since then, cascading methodology has made many followers, including the US Department of Defense.

Process of Waterfall Methodology

The cascade model consists of following a succession of predefined steps in a sequential manner, each step leading to the next one. This model is broken down into a series of six steps:

• Requirements (analysis of client’s needs);
• Conception;
• Planning (timeframe and budget);
• Implementation ;
• Verification;

It is a logical and sequential approach that aims to create the best possible final product.

By applying the waterfall method, the project team follows the specifications to the letter and works on the entire project until it is delivered. There is no interaction with the client who will receive his / her project once it is finished.

Everything must be planned in every detail. The team is committed to a precise schedule and defines all the tasks to be carried out. With this methodology, it is very complex to take into account changes as these will have an impact on all the current and future phases of the project, but also on the phases already validated, which will lead to delays and additional costs.

A Concrete Example

Here is an example to illustrate the waterfall methodology.

For the manufacture of a car, the customer orders the vehicle by catalog, taking care to choose all the details and options: the number of seats, the number of doors, the different materials (leather or fabric for the seats, plastic or wood for the dashboard, etc.), the color of the body, etc.

The car then goes into production where each step is carried out one after the other: stamping, assembly, painting and assembly. Each step must be completed to move on to the next. Indeed, the car cannot be painted if it is not fully assembled, and the interior cannot be mounted if it is not fully painted, and so on.

The customer can not intervene in the production process. He gets the car once it’s finished. If, in the end, the color does not please him, or if he prefers a five-door, rather than a three-door, he will then recommend a new car. He will have to wait again and certainly pay an additional fee depending on the new options.

Advantages and Disadvantages of Waterfall Methodology

Advantages

The waterfall method is simple, easy to set up, logical and structured. It adapts perfectly to projects that meet clearly identified objectives as well as projects where quality takes precedence over cost and time.

From the outset, the entire project is precisely defined and planned, which (in theory) makes it easier to estimate the budget, time and resources needed to complete the project.

The different stages follow one another in a rigorous order according to the deadlines, which allows the project to be delivered on time. This rigidity simplifies the management of the project, as well as the succession of the different phases without any overlap.

Disadvantages

The major disadvantage of this approach is its lack of flexibility due to its sequential operation. Indeed, the waterfall method leaves no room for changes and unexpected.

The risks of customer disappointment are greater. Since he sees the product only at delivery, he may be disappointed with the final result because his expectations have changed or the context has changed, and the project does not meet current needs.

All changes involve reviewing the project in its entirety (or almost all) as all phases will potentially be affected. This will generate significant delays and additional costs. For example, it will cost you much more to add an extra room to your already finished home, than if this room had been planned on the original plan. The cascade method is not suited to complex large projects.

In conclusion

The waterfall method remains one of the most widely used project management methodologies. Simple and logical, its strict organization makes it easier to establish the budget, time and work required for the project. This approach should be favored when the project has a clear vision from the start and the client does not have the opportunity to change the scope of the project once it has started. The waterfall method is often opposed to the agile method.