The physiography of Namdapha National Park and surrounding areas. Important mountain ranges, peaks, passes and rivers are shown.

Namdapha is classified as being in the Eastern Himalayan region. However, the park is actually sandwiched between the Patkai hills, an ancient hill range, in the south and east, and the comparatively young Himalaya to the north. The area lies close to the junction of the Indian and the Eurasian tectonic plates which makes it prone to earthquakes.

The valleys and foothill forests are drained by numerous snow- and rain-fed rivers, all of which form the catchments of the Noa-dihing River. The rain-fed Noa-dihing originate in the Chaka Bum range near the Chaukhan Pass along the Indo-Myanmar border and flows in an east-west direction through much of the park, and join the Brahmaputra river in the Assam plains. The river roughly divides the park into northern and southern halves.

The headwaters of the snow-fed, colder, fast-flowing Namdapha river originates in the snow-capped ranges around Dapha Bum to the north joining the Noa-dihing river near Firmbase. The park is bounded on the west by two big tributaries of the Noa-dihing, the M’pen nala and the Deban nala. Numerous smaller perennial streams and rivulets criss-cross the park.

The southern areas of the park have lower, relatively more undulating hills and shallow valleys, and the north is characteristically Himalayan – with tall peaks and deep gorges. Altitudes range from less than 200 m to over 4500 m above sea level. Dapha Bum, the highest point (4571 m) is a ridge of the Mishmi hills, and is at the park boundary with the Kamlang Wildlife Sanctuary to the north. The higher elevations are snowbound for most of the year, and the lower elevations are covered in forests and bamboo.

Towards the north, there are several peaks and passes (Mugaphi, Gaphuka, Hpungan) of the Himalayan range that are above 3000 m, while towards the southern boundary with Myanmar, there are a number of lower passes (1500 to 2000 m) in the forested Patkai hills.

It is the combination of Namdapha’s location and topography that influences climatic patterns in the area. Although temperatures depend on elevation and location (whether in a valley or on a slope), by and large, the months from November to February are the cold, relatively drier season. Sporadic showers occur in March and April; May is hot and largely rainless. June to October is the wet season. Temperatures at Deban, about 350 metres above sea level, range from 8°C on winter nights to 37°C on summer afternoons. Average winter temperatures range from 15° to 21°C and monsoon temperatures are between 22° and 37°C in the lower elevations. Temperature varies from 5°C to 35°C at lower altitudes and drops to below freezing point at higher altitudes.

Namdapha gets rainfall from both the southwest and the northeast (retreating) monsoons. About three-quarters of the rain (and there is a lot of it!) falls during the prolonged southwest monsoon months of June to October. During these months, most rivers swell and become impassable and the one path (the so-called Miao-Vijaynagar road) through the park becomes a river of mud. Rain from the retreating monsoon occurs in the months of December to March but this is nowhere as heavy and continuous as the wet months. According to Forest Department sources, total annual precipitation is 6300mm.

Namdapha National Park is rich in biodiversity because of its location at the confluence of the Indo-Malayan and Palearctic biogeographic realms and its straddling of two hotspots of global biodiversity (Eastern Himalaya and Indo-Burma). The plants and animals of the Indo-Malayan region are similar or identical with species found in Myanmar, Thailand and mainland southeast Asia. These are plant species such as dipterocarps and animals like clouded leopard, White-winged Wood Duck and several pit vipers. The Palaearctic species are similar to those present in central Asia and Eurasia. These include coniferous trees and birds like the Grey-headed Bullfinch.