This paper presents a methodology for examining the net benefit of site rehabilitation after an ecological disaster. While restoration of the site seems reasonable on the face of it, the cost of proactive restoration can be very high. In this article, we present a tool for decision makers to decide on the optimal route to rehabilitation – proactive or natural rehabilitation (or some combination thereof). We present a case study of an ecological catastrophe that occurred in June 2017 at an ephemeral desert stream in the south of Israel. We estimated the restoration costs and the benefits of restoration over the relevant time frame using a contingent valuation method. Comparing the present costs and benefits revealed a net present value of ILS 355.5 million in favor of proactive restoration of the stream. We also demonstrate that not all sections of the stream pass the benefit cost test, so a higher net benefit could be achieved through partial restoration. Our study demonstrates the importance of cost–benefit analysis when policy makers are contemplating proactive versus natural restoration.