Networks in Environmental Impact Assessment

The third common method of assessing impacts in EIA is called the Network method (checklists and matrices are the other two). This was first given by Sorenson in 1971, primarily to explain linkages between different environmental aspects. It is solely used to illustrate and understand primary, secondary and tertiary impacts of a developmental activity.

How is it done?

Networks are usually in the form of flow charts or radiation diagrams, as illustrated below.

Network showing effects of vehicular movement during the developmental activity.
Network as a flow chart.

A developmental activity is identified after which, all potential primary impacts are written down. From these primary impacts, secondary and tertiary impacts are identified and connected onto the network.


Networks help us follow the chain of events of a developmental projects, and its associated impacts. It can assess multiple impacts at the same time, helping us identify links that can easily be overlooked in the checklist or matrices forms of impact assessment. It can be aesthetically pleasing and easy to follow if done in a proper way. Often, networks are called “impact trees”.


However, networks do have considerable disadvantages. Unlike matrices, networks give no information at all about the magnitude and the significance of impacts. Further, no matter how hard you try, the networks can get very long and messy. This is especially the case if the project being assessed is a large scale project. In order to identify all levels of impacts, considerable knowledge of the environmental conditions of the project area is required. This puts impetus on the extent of detail in the baseline study. It is only preferred over other methods when multiple levels of impacts are expected at every stage of the development.

So, which to choose? Checklist, matrix or network?

Each form of impact assessment has advantages and disadvantages. Each form provides unique information that can be very beneficial in understand component interactions as well as activity component interactions. Some considerations for the selection of impact assessment method are-

  • The scale of the project- Generally, small scale projects go for checklists as it is comprehensive for that purpose. Medium scale projects can use either matrices or networks, depending on the potential impacts of the project activities. Large scale projects are better off using matrices.
  • Extent of detail required- Checklists tend to be more descriptive, whereas networks are quite simple in appearance. Matrices have the ability to be both descriptive or simple, depending on the type of matrix used.
  • Time available for the project- Sometimes, the EIA team is hard-pressed for time and cannot spend too much time figuring out all the implications of the activities.  They try to go for the most significant impacts and the description of these impacts.
  • Budget involved- This will, again, determine the amount of detail that can be generated from the baseline study. Budget has an indirect influence on the method of analysis used.

However–there is no hard and fast rule saying only one method of impact analysis need to be used. From what you have read in the last three blogs on impact assessment, you will appreciate that a mixture of matrices and networks will give you both, magnitude and significance of impacts, as well as the secondary and tertiary levels of impact. The team, if it considers it a good idea, can certainly go for both forms of impact assessment in order to get the most accurate information about the project area.

At the end of the day, the sole purpose of impact assessment is to identify all the impacts, then identify the important/significant impacts that arise through both direct and indirect relationship between activities and aspects.

This will help us move forward to the next step of the EIA process-prediction and mitigation.

Author: Saurab Babu

Usually found sitting with a good book, nibbling on a piece of dark chocolate. Always ready for a good story.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.