Aagh!! Multi-author page redirecting

I am working with a pre-established WordPress site with multiple authors. Each author has their own page accessible through a /author/{user_nicename} url, that displays their latest contributions. I do not know the actual page that is being displayed (i.e. the .php file; each author does NOT have a physical directory). I need to establish an alternate {user_nicename} that each user can be accessible by. There are so many authors that if I try to hard code redirects into the .htaccess file, it brings the site down.