Network survivability is one of the main design challenges in wireless sensor networks (WSN). Survivability is the ability of the network to provide essential services in the presence of attacks and/or failures, and recover full service in a timely manner. To the best knowledge of us, survivability for WSN has never been studied considering failure effects on network. We consider the network survivability as a composite measure consisting of both network failure duration and failure impact on the network. In this paper we model network survivability in steady state. In this state, network is affected by predicted failures. This modeling is based on network connectivity and coverage, when an area loses its connectivity; it is connected to the main node by using the covering nearby areas.