What is the waterfall methodology in project management?

When it comes to managing projects, knowing which methodology to use is crucial. By fully understanding what goes into each project management model, you can choose one that reduces cost, minimizes error and maximizes efficiency.

The waterfall methodology was first detailed in 1970 by the American computer scientist Winston W. Royce as a method for software development projects. Since then, it’s been adapted for use in several key industries, from construction to IT.

In this article, we’ll introduce the waterfall methodology, explain its main uses, benefits and drawbacks, and then compare it with some of the other major project management models.

What is the waterfall methodology?

The waterfall methodology involves breaking down each part of a project into clearly defined, sequential phases. The word “waterfall” illustrates the way that water flows in one direction down a waterfall, as you can only complete each project stage in order – no backtracking is allowed.

Imagine a series of pools separated by waterfalls. These pools represent each stage in the project management timeline, from planning to development to release. The water can’t reach the next pool until it is full and overflows into the next. Likewise, using the waterfall method, you only move on to the next stage when the current stage is 100% complete.

There are three basic principles to the waterfall methodology:

• Strict, one-way structure. When using the waterfall method, you split your project into discrete stages. You must complete each stage in order. There’s no going back or changing course if something unexpected happens. Instead, if something goes wrong, you must start at stage one again.

• Little to no stakeholder involvement after the first stage. Due to the structure of the waterfall methodology, you must document all stakeholder interactions in the first stage. After this, due to the strict structure of the waterfall model, there’s no way to implement changes and stakeholder communication ceases.

• In-depth upfront documentation of the entire process. To solve some of the limitations of the waterfall method, documenting each stage in detail upfront is critical. As you won’t be able to receive feedback from clients throughout the process, you need to make sure to document all essential requirements before starting the project.

The waterfall approach has been popular in the construction industry where there needs to be a strict order to activities. In construction, once a stage has been completed, it’s often irreversible. For example, there’s no way to “unpour” concrete. Similarly, you also can’t begin laying bricks until the concrete foundation is down.

However, it has since been adapted more generally to project management as a whole. It’s especially well-known for its use in software development to create products like customer relationship managers (CRMs) and similar project management tools.

The benefits and drawbacks of the waterfall methodology

The waterfall methodology works best in very specific use cases. Due to this, it has several advantages and disadvantages that can make or break your project.

The benefits of the waterfall methodology include:

• A fixed budget and timeline. Using the waterfall model, all goals and requirements for the project are delineated upfront. There is little to no feedback and collaboration, and the project simply progresses through milestones toward completion. This means that your projected budget and timeline are unlikely to change.

• Extensive planning makes implementation easy. Since you put so much effort into documenting and planning your project at the beginning, you’re more likely to invest your time and money optimally. This prevents you from wasting either and ensures that the project will be more streamlined.

• A streamlined process means it’s easy to manage. Due to the rigidity of the process, each phase has specific deliverables and milestones, making it easy to manage (and track).

• A simple structure means you can duplicate projects. The waterfall methodology is straightforward, especially compared with more complex project management methods. If you often conduct similar projects, you can use much of what you developed for previous projects to inform new ones.

• Adaptability to varied applications. Take the demand lifecycle. It can be approached using the waterfall method by adopting key principles – like consistent, upfront documentation – and reframing the sales funnel as a one-way waterfall through the steps of lead generation, marketing qualification, sales qualification and finally closing the deal.

However, there are also several disadvantages to using the waterfall methodology:

• High risk and uncertainty. As the entire project is laid out in advance (and there’s no going backward), there’s a certain level of risk when using the waterfall methodology. For example, if the intake process was rushed or incomplete, stakeholders might not be happy with the final product some time later – meaning wasted time and effort.

• Too rigid for complex or ongoing projects. The waterfall methodology cannot accommodate changing requirements. For this reason, it’s unsuitable for projects where the goals have a decent chance of changing.

• Quality control is late in the process. Many project management methodologies have iterative review stages peppered throughout development. Not the waterfall method. Unfortunately, this means that early mistakes can lead to big problems down the line.

• Clients and stakeholders often don’t fully know what they want. Many clients or stakeholders will realize during development that they need extra functionality from your product. The waterfall methodology leaves no room for this possibility, making it difficult to accommodate requests for changes after completing the first stage.

The benefits of waterfall methodology	The drawbacks of waterfall methodology
A fixed budget and timeline	High risk and uncertainty
Extensive planning makes implementation easy	Too rigid for complex or ongoing projects
A streamlined process means it’s easy to manage	Quality control is late in the process
A simple structure means you can duplicate projects	Clients and stakeholders often don’t fully know what they want
Adaptability to varied applications

When to use the waterfall methodology

While the waterfall methodology is a powerful process for certain projects, it isn’t suitable for all of them. You should use the waterfall methodology when:

• Your project is clearly defined, simple and unambiguous. The waterfall project management methodology works best on small, clear projects where you can lay out everything in advance. If your requirements are vague, you may need to use a different project management technique.

• Your project’s requirements won’t change. If your project might change course halfway through, you’re better off using a more flexible project management methodology. The waterfall project management methodology is a rigid system and changing requirements often means starting over again.

• You have time to plan. The waterfall methodology requires a significant investment of time in the early stages before starting on development. If you don’t have the time to invest at the beginning, you should use a different model.

If your project ticks all three of these boxes, the waterfall model will probably work well for you. However, if you’re unsure about any of them, you’re probably better off choosing a more flexible project management method like the Agile methodology. More on this below.

The five phases of the waterfall methodology

The waterfall methodology follows five different phases: Requirements, design, implementation, verification and maintenance. Here’s what each of the phases looks like.

1. Requirements phase

In the requirements phase, the project team meticulously plans the entire project baseline from start to finish. During this phase, the project team will collaborate with the client to find out everything they need to know to produce the final product without consulting the client again.

The requirements stage is the most important stage in the waterfall methodology because it lays the foundation for your entire project. If you miss pertinent information or fail to document your client’s or stakeholder’s requirements in sufficient detail, you’re going to face a massive headache when they receive a product that isn’t what they wanted.

During the requirements phase, you should determine the following:

• Project scope and timeline. Create a requirements document that lays out the goals for your project, from the functional requirements to the deliverables, dependencies, deadlines and associated costs.

• Stakeholder expectations. You need to work out exactly what your client wants. From functionalities to timeline, it’s important that your client is 100% onboard before starting, as they will have minimal opportunities to chime in once the project has gotten started.

• Market status. Market research is vital for any product development lifecycle. Depending on your product, you will likely have to know about competitors, the market environment and customer needs in order to develop a competitive product.

2. Design phase

In the next phase, it’s time to review all of the information gathered in the first stage and develop a detailed plan. At this stage, you will decide on the overall project plan, including a design for your product.

The system design stage is often split into two separate steps.

• High-level design. Also known as logical design, this is where you and your team come up with possible ideas for the development process. During this stage, you’ll develop a set of theoretical plans for making the final product a reality.

• Low-level design. Also known as physical design, this is where you narrow down your theoretical ideas into a concrete plan. In this step, you will decide on the required tools and techniques and create an overall blueprint for your product. In software development, you would specify the tools, hardware and overall architecture for your project.

After the design phase, you should have a clear idea about what the final product will look like and what steps you need to take to get there.

3. Implementation phase

This is where the fun begins. In the implementation phase, you take everything you’ve planned and put it into action. Your team will take the workflow documentation and begin to produce the final product.

Since most of the work happens at the start of the project with the waterfall method, this may be one of the shorter (if not the shortest) stages in the process.

To begin the implementation phase:

• Assign tasks to team members. With your design plan already produced, assign key team members to each task. It’s a good idea to use capable project management software, like a project management CRM or a Gantt chart.

• Monitor progress. Once you get started, your job as project manager is to ensure that the project continues moving forward. You also need to monitor resources and allocate workload to alleviate bottlenecks if they occur.

• Report to stakeholders. While the waterfall methodology typically limits client interactions after the project outline, you should still report your progress temporarily – especially for longer, more complex projects. This lets your clients know you’re still on track, putting their minds at ease.

4. Verification phase

At the end of the previous phase, you should have a near-completed product – now it’s time to take it through a testing phase. This is arguably the most nerve-wracking phase, as any significant issues could mean starting from scratch.

During the verification phase, you need to ensure that everything is working correctly and all client requirements have been met to high standards. The product also needs to be rigorously tested for issues so you can address them before releasing the product to the client.

If everything is looking good, it’s time to deploy your product.

5. Maintenance phase

This phase of the project occurs after you deliver the final product to your customer. However, this phase will vary significantly depending on the nature of your product and the agreements you made with your clients.

In some cases, maintenance can occur until your client is satisfied with your product. If, on the other hand, you launched your product on the market, maintenance may continue indefinitely.

The main activities of the maintenance phase include:

• Ironing out any issues, bugs and glitches missed during the verification phase.

• Introducing updates to the product that boosts its performance, keeps it up to date or improves it in some way.

Even if you invested significant resources into the quality control process, it’s impossible to find everything. Often, key issues are only noted once the product is in active use. That’s why the maintenance phase relies so heavily on customer feedback.

How the waterfall method compares with other popular methodologies

The waterfall methodology is just one of many project management models and isn’t suitable for every kind of project. Here’s how the waterfall method compares with three other popular project management models: Agile, Kanban and Scrum.

Waterfall methodology vs. Agile

The Agile project management methodology is a flexible, iterative approach to project management. Unlike the waterfall method, the Agile approach is focused on rapid delivery while leveraging a high level of customer involvement.

The Agile method breaks up a project into several smaller parts that teams develop simultaneously and incrementally. Teams typically work on the deliverables over a short period of time – usually 1–2 weeks.

During these weeks, the team and client collaborate to work out what needs to be added to get it closer to the final product. At the end of each increment, the work is reviewed by the project team and customer and new deliverables are defined if need be.

The main differences between the waterfall and Agile methodologies include:

• Agile is flexible and adaptable, while the waterfall process is rigid and well-organized.

• Agile is iterative, improving with each cycle. Waterfall development methodology is linear, progressing in one direction through each phase.

• Agile is divided into increments and the planning, implementation and verification stages occur during each iteration. Waterfall is planned in advance, with planning, implementation and verification occurring once each at distinct times.

• Agile is designed to allow project teams to adapt to changing systems. Waterfall is designed for predictable, reliable outcomes using a predefined process.

Waterfall vs. Kanban

The Kanban project management approach uses Agile methodology principles but implements them in a slightly different way to improve productivity. Teams visualize tasks using a Kanban board, where each activity is assigned a card that moves from column to column as it nears completion.

For example, a task may move through columns labeled “Assigned”, “In progress”, “Testing” and finally “Complete”.

Like Agile, the Kanban method works best for different types of projects than the waterfall method. For example:

• Kanban is focused on continually improving a product, whereas waterfall is designed to create a clearly defined product, without adding improvements.

• Kanban can adjust to mid-project changes, while waterfall cannot.

• Kanban often results in scope creep, where stakeholders’ opinions and requests continually change throughout a project. Waterfall mitigates this by laying out project requirements upfront.

• Without specified timelines, projects using Kanban may take longer than the clearly defined timeframes set out using the waterfall technique.

Waterfall vs. Scrum

Scrum project management is another Agile-based methodology. While Kanban focuses on continually improving processes, the purpose of Scrum is to get work done faster.

Scrum splits increments into two-week sprints. These are planned and tasks are outlined in a backlog. Then, teams execute individual tasks and review progress at the end of the two weeks. Each day, the teams hold a Scrum meeting where they briefly discuss obstacles and plans to keep things on track.

The Scrum approach requires that team members take on key roles. There’s the Scrum Master who facilitates the team (without managing them), moving the project forward and addressing obstacles. Next, there’s the Product Owner, who communicates the client’s expectations to the development team.

Finally, there’s the Development Team, who’s responsible for creating and testing the product until completion.

Here’s where Scrum and waterfall differ:

• Scrum requires a fair amount of familiarity to employ. Your team needs to understand how Scrum works, along with the terminology and roles that are unique to the process. On the other hand, Waterfall is incredibly simple to understand and employ.

• Scrum has no set completion date, introducing the risk of scope creep. With the waterfall method, this isn’t an issue as the requirements phase details everything in advance.

• Scrum can accommodate changes as required after each sprint. Waterfall is inflexible and unable to course-correct as the project continues.

Final thoughts

Deciding on the correct project management methodology is one of the most important aspects of successful projects.

Remember that while it’s generally recommended to follow the major principles of each method, you can adapt them to your requirements.