Katarniaghat Wildlife Sanctuary is a part of the Dudhwa Tiger Reserve. It is managed along with the Dudhwa National Park and Kishanpur Wildlife Sanctuary. The Katarniaghat Forests provide strategic connectivity between tiger habitats of Dudhwa and Kishanpur in India and the Bardia National Park in Nepal.

The Gairwa river which flows in the sanctuary area is declared as a sanctuary for Mugger and Gharial. It is also home to rare turtles, freshwater fish and a host of aquatic life. The river presents a scenic view on both banks with long forest tracts running into the distance and overhanging trees on the river bank creating coves that attract visitors on motorboats. The sanctuary has a mosaic of Sal and Teak forests, lush grasslands, numerous swamps, and wetlands.

One of the best places in the world for seeing the gharial in its natural habitat is the Girwa River, where it is found sympatric with the mugger. The population of gharials in this stretch was one of the three that were still breeding when the project to conserve this reptile from the verge of extinction was initiated in 1975. However, between the years of 2001 and 2005, almost all the gharial nests were raided by tribals who consider them a delicacy.

Mugger crocodiles are also seen in small number in the Girwa river, as their favorite haunts are stagnant wetlands like the many taals and baghars that dot the sanctuary. Side by side the serenely swimming gharial can be seen frolicking Ganges dolphins.