@BangalorewebzoDec 15.2014 — #Yes In single page website dont need HTML and XML sitemaps. Sitemap mainly used for Large number of pages websites only . so dont worry about sitemap.
@anirban09PJan 13.2015 — #An HTML site map is a single HTML page that contains links to all the pages of your website. Normally, this is accessible via a link in your site footer, where it will be displayed on every page. With large sites, it is easy to get lost and struggle to find the page you are looking for. With a well organized HTML site map, your site visitors will be able to use this to easily find the page they are looking for.
An XML sitemap is a document that helps Google and other major search engines better understand your website while crawling it.
In Simple words,A site map is a visual or textually organized model of a Web site's content that allows the users to navigate through the site to find the information they are looking for, just as a traditional geographical map helps people find places they are looking for in the real world.
It does not matter whether where your site is single page or having Multiples pages but If your site is new, or if you have a significant number of new (or recently updated pages), then using a sitemap can be vital to your success.