IMPACT ASSESSMENT AND RISK-BASED IMPACT ASSESSMENT

Hello, everyone. This is my first time writing a new topic.
I want to get to know about impact assessment in Change control. But I dont know how many methods to do impact assessment and is impact assessment different from risk-based impact assessment? . It seems like doing impact assessment is easier than doing risk assement.
Can you recommend some documents abour this for me because i am composing SOPs . Thanks in advance