What is a waterfall model? 

The waterfall model is one of the first and most widely used project management methodologies. It used to be widely used in software development, but because it is less applicable in a volatile environment, agile methodologies are now used instead. However, it is still used today in many industries, such as construction. But what exactly does the waterfall model mean, what are its advantages and disadvantages, and in general: for which projects should this methodology be used? In this article, we've explored the topic.

For which projects should the waterfall model be used?

• Where project requirements are pre-defined, the industry is not characterised by rapid change 
• If the project outcome can be created with existing technology, so no extra R&D is needed
• If you do not need continuous client-side feedback on the results achieved
• If the task is well planned and the expectations are clear and unambiguous 

Such projects could be, for example, construction projects or investment projects for large companies. 

Phases of the waterfall model

The waterfall model uses a sequential way of thinking, which, as the name suggests, resembles a waterfall. As mentioned above, each stage is typically sequential. Each stage may vary from industry to industry, or may be defined by the technical content of the tasks to be performed, or by management and work organisation aspects. For example, what are typical phases? 

#1 Setting requirements and objectives

This is the stage where the project's purpose, key requirements, guidelines and deadlines are broadly defined. There are no concrete implementation plans or process. 

Once this has been done, a feasibility study is carried out, a risk analysis is carried out and it is also checked whether the project will actually pay off. From all this, a so-called business case (business plan) is prepared, and once approved, the project can really start. 

#2 Designing the project

Careful project planning is essential for successful implementation. A common problem is that insufficient time and resources are devoted to the planning phase, leading to cost overruns, delayed deadlines or even non-compliance with requirements. In such cases, unfortunately, the project cannot be considered a success. 

Projektterv

The most important document of the planning phase is the so-called project plan document, the most important elements of which may vary from one organisation or industry to another: 

• Roadmap for action
• WBS structure definition - this refers to the structure of the work breakdown
• Assignment of tasks - task-responsibility matrix
• Resource planning e.g. using an activity-resource matrix and a cost plan
• Scheduling e.g. using a Gantt chart
• Risk analysis
• Communication plan
• Contact management plan
• Managing suppliers

#3 Project implementation

This is the stage where the real work starts, i.e. the practical implementation of the project. The key elements of this phase are risk management and change monitoring and management. It also requires active and lively communication between stakeholders and the project team. 

#4 Inspection and testing

Once the project result is ready, a comprehensive check and testing is needed. This is always done by pre-defined requirements during the design phase of the project. Any errors detected are corrected at this stage. The next, final phase can only start once the client has accepted all the details of the project. 

#5 Completion of the project

Once the project is completed, the project will be formally handed over, commissioned and start operating. At this time, all contracts and documentation need to be reviewed and archived. During the project closure meeting, it is essential to draw lessons learned during the project and to keep them in a repository, if possible, for use in future projects. Part of the project closure is the allocation of project team members to a new project.