In many application scenarios, wireless sensors are deployed deterministically throughout a wide area to detect and report specific events or monitor environmental parameters. To cover a large area with minimal number of sensors, it is important to determine sensing radius of the operating sensors. Since the emitted energy of a random event is neither predictable nor fixed, accurate sensing radius modelling is a challenging problem. To the best of our knowledge, no work has considered how the event intensity factor reduces probability of event detection while assuming a sensing radius despite its high significance in important areas such as coverage, detection, localization, etc. In this paper, we have proposed a novel stochastic model of the maximum sensing radius to guarantee a user-defined event detection probability from the pdf of average event intensity and the quality of sensors. Comprehensive theoretical and numerical analyses are presented to evaluate the event detection performance of this model against different relevant parameters and these are also verified by simulation. Provision for event location trajectory computation is analysed for high-intensity events.