Waterfall methodology: advantages and limits of this project management approach

It is always advisable to find the best way to manage a project. Fortunately, the waterfall methodology is one of the most widely used project management methodologies, helping teams manage their projects effectively and optimise their performance. Studying the waterfall model can help you discover how to organise your project in a clear, linear way. But this approach also has weaknesses that it is essential to understand before applying it.

What is the waterfall methodology?

The waterfall methodology is a linear, sequential approach to project management. It relies on a rigid sequence of phases, where each stage must be completed before moving on to the next. The project thus follows a structured course, like a waterfall flowing from top to bottom in successive drops: requirements analysis, design, development, testing, deployment, then maintenance.

This model emerged in the 1970s, at a time when IT projects required strict planning and complete documentation. Its main strength lies in its clarity: each phase is defined from the outset, deadlines are known, and deliverables are precisely specified at each stage.

Still widely used today in sectors such as construction, engineering and embedded systems, the waterfall method remains a historical benchmark in project management. But it is not suited to every situation, particularly in environments where needs can change quickly.

What are the stages of waterfall project management?

The waterfall methodology relies on a succession of logical stages, where you only move on to the next one once the previous one is fully completed. Waterfall project management can be broken down into six main phases.

Defining requirements

This initial stage is crucial: it involves gathering all the requirements of the client or end users. These requirements are then formalised in a detailed specification, which will serve as a roadmap for the whole project. At this stage, it is important not to forget anything, as changes made along the way are hard to incorporate.

Functional and technical design

Once the requirements are clearly defined, the teams draw up the architecture of the project. This includes functional design (what the product or service must do) and technical design (how it will be built). It is a phase of rigorous planning, which will determine the resources needed, the tools used and the deadlines.

Development or implementation

This is where the project takes shape. Developers or operational teams build the solution, following the previous specifications precisely. No major iteration or adaptation is planned at this stage: what has been defined is applied, in order, with discipline.

4. Testing phase
Once development is complete, the verification phase begins. Testing makes sure that the product or service works as intended, without bugs or inconsistencies. Any deviation from the specification is identified so that it can be corrected. It is an essential stage for guaranteeing final quality.

Deployment

After validation, the solution is put into production: it is delivered to the client or deployed in their real operating environment. In the waterfall method, this moment marks the very first encounter between the end user and the finished product.

Advantages and disadvantages of the waterfall method

A clear, rigorous structure

The main advantage of the waterfall method lies in its simplicity of implementation. Each phase of the project follows logically from the previous one, which makes planning and the allocation of tasks easier. For project managers, it is a reassuring model that offers an overall view from the outset.

    
Precise documentation

The very detailed design phase requires a complete specification. This clarifies the expectations of all stakeholders before the start, thereby reducing the risk of differing interpretations.

Better control of costs and deadlines

Because all the stages are defined in advance, the budget and schedule can be estimated more accurately. Surprises are rare... provided that requirements do not change along the way.

Suited to simple or regulated projects

Waterfall works well for short projects that change little or that require strict compliance, such as constructing a building.

The disadvantages of the waterfall method

Lack of flexibility

This is the main criticism levelled at this model. If requirements change or new constraints appear, it is very difficult (and costly) to go back. Waterfall does not adapt easily to changing environments.

Little user involvement during the project

In the waterfall method, the client only sees the product at the end. This can lead to a gap between initial expectations and the final result, particularly if usage has changed in the meantime.

Risk of late error detection

As testing takes place at the end of the project, errors are sometimes detected only when it is too late, which may mean redoing a significant part of the work already completed.

Waterfall methodology vs. the agile method

Faced with the limits of the waterfall method, particularly in uncertain or complex environments, the agile method has established itself as a more flexible and interactive alternative. But these two approaches follow very different logics.

The waterfall method relies on a linear sequence of predefined phases. You move from analysis to design, then to development, testing, deployment and maintenance, with no possibility of going back. Everything is planned from the outset. The agile method, by contrast, relies on short cycles (called "sprints") that allow rapid iteration. The team delivers a working version of the product at each sprint, tests it, corrects it and improves it based on user feedback. This method adapts continuously to changes in the project.

In a waterfall project, changes are hard to incorporate once the development phase has begun. This can be a problem if requirements change along the way.
The agile method, on the other hand, welcomes change as a normal part of the project. It allows the product to evolve step by step, regularly involving the client or end users.

In waterfall, the client is mainly present at the beginning and the end of the project. They express their needs, then approve the final result. This can lead to gaps between what was envisaged and what is delivered.
In agile, the client is an active member of the project, consulted at every stage. They can test intermediate versions, give feedback and adjust priorities. This co-creation strengthens the relevance of the product.

Is the waterfall method right for your project?

It all depends, of course, on your project and on how you wish to run it. The waterfall method can indeed prove very effective in some contexts and entirely unsuitable in others.

As explained above, the waterfall method is particularly suited to well-defined projects whose specifications are clear, stable and unlikely to change along the way. This is the case, for example, in industry, infrastructure and regulatory projects where strict adherence to deadlines, budget and scope is the priority. The linear progression of the method then offers valuable visibility and complete documentation at every stage.

On the other hand, if you are working on an innovative, user-centred project where needs can change quickly, the agile method or a hybrid approach will probably be more appropriate. A framework that is too rigid can slow down decision-making, limit adaptation to change and ultimately compromise the success of the project.

Before choosing your method, ask yourself about several criteria: the project's level of maturity, the clarity of the requirements, your company's culture, the availability of resources, and the degree of collaboration you want with stakeholders.

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Since its creation, the waterfall methodology has been the subject of much debate, for and against. However, it remains highly relevant in today's market, even if other methods, such as the agile methodology, have evolved more quickly. If you have a small team with limited resources and fixed objectives, the waterfall methodology is an excellent way to optimise and streamline the project development cycle and deliver a high-quality finished product. So, ready to start the cascade? Dive in!