The limestone hills of Erawan National Park rise 165 to 996 meters above sea level. Many important streams flow from these hills. On the eastern side of the park, Mong Lai stream and Omtala stream join together above Erawan waterfall. Sadae stream flows through the north side of the park to Si- nakharindra dam. In the west, Nong Kop stream joins Sai Yok river, and these waters then flow through Sai Yok waterfall. Many small streams flow through the southern part of the park, including the Khao Phang stream which boosts the beautiful Khao Phang waterfall, also known as little Sai Yok waterfall.
These mountains protect the park from the eastern monsoon resulting in a low average rainfall. Rainy season starts from May to October, when storms come from the southwest and the northeast. Cold season runs from November to January, when the weather is cool and pleasant. February to April is the hot time and temperature is quite high. The park is open all year.
The main prevalent forest type in Erawan National Park is the mixed deciduous forest covering 81 percent of the park area. Common tree species are Afzelia xylocarpa, Hopea odorata, Pterocarpus macrocarpus, Spondias pinnata, Lagerstroemia spp., Thyrsostachys siamensis, Bambusa bambos etc. Other forest types are dry dipterocarps forest and dry evergreen forest community which possess the area with dominant species like , Shorea obtusa, S.siamensis, Quercus kerrii, Sindora siamensis, Chukrasia tubularis, Polyalthia viridis, Fagraea fragrans and several different bamboo species.
From field observations, the park contains 5 different wildlife habitats for mammals, reptiles,
amphibians, birds and freshwater fauna. The already enlisted animals are Indian elephant, tiger,
Serow, Common muntjac, Sambar deer, Wild boar, White-handed gibbon, PhayreŻs langur, Siamese hare, Red flying squirrel, Kalij pheasant, Grey peacock Pheasant, Red-wattled Lapwing, Crested Serpent-Eagle, King cobra, Banded krait, Asiatic rock python, Asiatic apitting, Greater brook carp, Striped tiger nandid, and waterfall crab (Potamon erawanensis)