Waterfall Methodology

The Waterfall model organises a project into sequential phases — each one completed and approved before the next begins, like water flowing down a series of steps. It is the classic example of a predictive approach: scope, schedule and budget are planned in detail up front, then executed and controlled against that baseline.

Typical Waterfall phases

1. Requirements — capture and sign off everything the solution must do.
2. Design — define the architecture and detailed design.
3. Implementation — build or construct the solution.
4. Verification — test against requirements.
5. Deployment — release, hand over and train users.
6. Maintenance — support and fix issues in operation.

Each phase ends with a formal review, and changes to an approved phase go through change control.

Advantages

• Predictability: a full schedule and budget early on supports contracts, funding and regulatory approval.
• Clear documentation: useful for audit, handover and large distributed teams.
• Simple to understand and manage for stakeholders used to milestone-based reporting.
• Efficient when change is expensive: it is cheaper to change a drawing than a poured foundation.

Disadvantages

• Late feedback: users often see the result only at the end, when change is most expensive.
• Assumes requirements can be known up front — rarely true for new products.
• Risk accumulates until testing and integration, where surprises cluster.
• Long time to value — nothing is usable until the final phase.

When Waterfall is the right choice

• Construction, manufacturing and infrastructure, where work is physical and sequential.
• Regulated projects requiring full design approval before build.
• Fixed-price contracts with well-understood scope.
• Repeat projects where the team has done the same thing many times.
• Events with an immovable date and a well-known checklist.

Making Waterfall work better

• Prototype early: show mock-ups during requirements to surface misunderstandings.
• Use rolling-wave planning: plan the near term in detail and later phases at a higher level.
• Manage the critical path and protect it with contingency — see the CPM calculator.
• Track with earned value for objective progress (EVM calculator).
• Test continuously instead of only at the end.

If several of these "agile-like" practices appeal, you may be heading toward a hybrid approach.