Vonnie
Yes you should declare and provide as much information as you have available. What caused the flood in the Garden?
See other thread for related question/answer.
http://www.moneysupermarket.com/community/forums/t/home-insurance-what-is-classed-as-flooding-35737.aspx
Have you asked the Insurance company why the premium has increased by £150? If,so what reason did they give you? In theory if you declared the flooding the premium you paid took this into account. If 12 months has passed and you have not claimed on policy why would Insurers increase the premium by this amount? Is there a flood risk in your postcode area and this has led to Insurers increasing the premium rate? Insurers do compile alot of risk information, taking into account a lot of factors, including flooding. Insurers may therefore know from your postcode whether there has been a problem in your area.
huckster