The Waterfall model in project management
What is the Waterfall model and how does it work?
The model works with sequential phases that are planned down to the smallest detail, with a clear start and end point that flow into each other. In order to define these clear points, at the beginning of the project the exact requirements of the companies, customers or stakeholders are identified. With this information, the content of each phase can be precisely planned and successfully delivered. This increases efficiency, but also makes the process very inflexible and rigid. As the model is sequential, there is usually no feedback between the individual phases, i.e., the planned phases are carried out until the end of the project without any return. For this reason, it makes sense to use this method if few changes are expected. However, it has advantages and disadvantages, which are discussed below.
The phases of the Waterfall model
- execution and
At the end of the description of each phase, an example of an investment project is given to show how each phase could be designed. For example, a new plant is to be built for the production of a certain material.
The next step is the stakeholder and environment analysis. This involves systematically recording the interests and influence of stakeholders. Not all stakeholders have a positive attitude towards a project or have varying degrees of influence. Once this is known, each stakeholder can be dealt with accordingly. But the internal and external environment can also influence the project, for example through communication with stakeholders. Therefore, it makes sense to link these two points together.
In addition to stakeholders, customers also have expectations of the project, which should be captured in a requirements analysis and prioritisation. It should also be checked whether these expectations can be met.
It is helpful to have a complete specification, which contains all the necessary requirements from the customer and is given to the project manager. This should be as detailed as possible to enable accurate planning. Once the expectations and requirements are known, a risk analysis can be carried out to assess, evaluate and prioritise the risks.
In the event that problems arise during the course of the project, measures to prevent or detect errors should be defined in advance. To do this, it is necessary to plan the project as precisely as possible so that it does not happen in the first place. If it does, it can trigger a cascade that can lead to time delays and additional costs, which will be discussed later.
It is also important to repeat the risk analysis, because even with the most careful planning, new developments can always occur.
Since the project is only tested at the end, change management should be established from the outset to know how to deal with any errors. Even with the most accurate planning, there will always be unforeseen developments that need to be responded to. It is particularly important that changes are clearly communicated to everyone to avoid duplication of effort.
This step also considers the tools, technologies and working conditions required to complete the project, as well as a documentation strategy. This addresses how documents relevant to the project will be managed. Documentation includes creating, identifying and recording, summarising, editing and updating, distributing, archiving and destroying documents. The underlying strategy includes decisions about how the documents produced will be stored and managed, and who will have access to them. The documentation strategy should ensure that all relevant information is accessible and understandable to the responsible person so that the documentation supports and does not hinder the project.
Phase P0, the basic planning, includes the project plan and the plant concept. For the planning, all people involved assume two months, with a budget of 40,000 CHF.
The definition is important because depending on the type there are different approaches, and each has different risks or requires different documents.
The distribution of roles can be as follows: A project leader, who takes on many responsibilities for the duration of the project to make it a success. The project team, which may consist of a few or many team members who contribute to the success of the project through their required expertise. The composition of the project team may vary from phase to phase. For example, at one stage the team may consist only of developers, at another stage of engineers, and at the next stage of builders. And the steering committee, made up of members to whom the project leaders report.
The next step is to agree internally how the project will be organised. This includes the composition of roles and who has what authority. The Waterfall model is often associated with traditional project management, with three organisational structures. In the staff organisation, the project manager has a very limited function. He has no authority to issue directives and is limited to informal exchanges. In the matrix organisation, the project participants have two superiors, the project manager and the head of department, because the competences of the departments overlap. However, this form of organisation is only recommended for larger companies, as it allows for specialisation in several areas. Team members report to both the project manager and the head of department, so the information gets where it needs to go. The third is the autonomous organisation. Here the project manager is solely responsible for the project team, the implementation and the outcome of the project. He is ultimately accountable only to the steering committee. It is advantageous to have a defined communication structure, as the way of communication has a direct impact on the organisation.
Of particular importance is the definition of the project objective, which contains the result to be achieved and is a prerequisite for the fulfilment of the overall task.
The specifications prepared by the contractor are helpful as they contain all the requirements. Once all this is known, the implementation concept can be approved, and the project-specific phase can be planned. The individual milestones of each phase are defined and additional acceptance criteria for changing phases are set. It is also important to create a Work Breakdown Structure (WBS). The WBS is divided into sub-projects and work packages. Work packages are the smallest unit in the WBS and contain the activities required to complete a task, as well as an estimate of duration and cost. This estimate can be used to combine the costs of the sub-projects into the project costs in a bottom-up manner, or to allocate the available budget to the work packages in a top-down manner. By dividing the project into work packages and phases, a schedule can be created that leads to the critical path. This is the longest process chain and is a process without a buffer.
Phase P1, which represents the kick-off. In this phase, details have been carried out, building permits have been obtained and the budget has been discussed. This phase can take up to three months and has a budget of CHF 60,000.
If errors occur, they should be evaluated and corrected. However, if the test went well, a product presentation can be made.
This should be followed by a project review with all stakeholders. This will assess whether the objectives have been achieved, whether there are any outstanding issues, etc.
P2, the implementation phase, and P3, the construction phase, which includes tendering and contracting, which can take up to three months, and implementation, which takes nine months. The budgets are CHF 100,000 and CHF 500,000 respectively.
If the product requires maintenance, this is also discussed.
Phase P4, the project closure. The project is handed over.
Advantages of the Waterfall model
As each phase must be completed before the next one begins, no work is left undone. This makes the method clear, intuitive and requires no special training. Documentation is easy to follow, as all information is documented, making it easy to trace each phase.
Disadvantages of the Waterfall model
It is only at the end that you find out if a project is successful, and if it is not, the worst that can happen is that the project is extended, and the costs explode. In addition, in long-term projects, the final product may already be out of date, and an established change management process may be required to deal with the situation.
Examples for the use of the Waterfall model
Another example of projects that should not take too long because they cannot be changed is software projects, such as the development of a website, because any changes will not add too much time to the overall schedule.
Best practices when using the Waterfall model
The model already contains many approaches that are important for implementation. These include precise project plans with defined start and end points for each phase, risk management that is established at the beginning of the project and updated as necessary throughout the project, regular communication with all stakeholders to keep the project on track and everyone informed, and good documentation so that each step can be traced.