While this question is 3 years old, it does not have a sufficient answer. For others concerned with this topic:
Redirection is the least of my concerns here. 301 redirects get applied if there is a replacement destination. Use 404 or 410 if you're deleting a category or have no logical replacement.
Consider this example:
-> SEO // Level 1
-> Technical SEO // Level 2
-> Website Audits // Level 3
The organization of a website is subjective, Google does not care about folder depth. The URL below is long, but it has the same potential as a very short URL.
What Google does care about is the number of clicks from your home page is. Generally, pages that you want to rank should be easy to get to from the home page.
Page Rank Dilution
A reason it needs to be easy to get to from the homepage is because crawlers find pages via links, links are like doors. Your homepage also holds all of your Page Rank, the more doors it takes to get to a page, the less page rank the final URL will receive.
Recall our example:
If you want to rank the
/website-audits page it needs either:
- A lot of incoming internal links from pages within /seo/ or others at the same level
- To have internal links to from home or /blog
- Else, it needs a handful of backlinks from relevant websites
All three of those would be ideal. Also, the 301 redirects will pass page rank, don't worry about losing it.