[2] Originally Angammedilla was a forest reserve within the Minneriya-Girithale Sanctuary declared on 12 February 1988.

[1] Angammedilla also secures the drainage basins of Minneriya and Girithale irrigation tanks, water sources in Sudu Kanda (Sinhala for "White hill") and habitats and wildlife of the adjacent forests.

Amban river which is sourced by Sudu Kanda forms the southern border of the park.

In the ancient times water has irrigated from Amban river to Parakrama Samudra in a canal done in stone.

Manilkara hexandra (Palu), Cholorocylon swetenia (Burutha), Vitex pinnata (Milla), and Adina cordifolia (Kolon) are common in natural vegetation.