Rock slope instabilities, such as rockfalls and rockslides, can threaten human life along major transportation networks and recreation coastal areas, affect safety during infrastructure construction and significantly interrupt transportation along highways and railways with substantial economic losses. Accurate predictions of the associated risks and their effective reduction require a thorough collection of rock mass structural conditions and triggering events’ evolution with time to infer appropriate modelling parameters for the design and implementation of the most suitable mitigation measures. Close-range terrestrial photogrammetry and Unmanned Aerial Vehicles (UAVs) have been used to monitor hazardous and hardly accessible rock slopes located above popular recreational areas along the Newcastle coastline in NSW. Valuable inventories of rock mass structural data and rockfall spatial–temporal occurrence and magnitude have been collected to identify major structures affecting rock slope stability and sources of rock instabilities (detachments) over extended periods of time. Their volume and frequency have been accurately estimated. Results highlight the crucial role played by the identification of appropriate input parameters to adequately simulate realistic rockfall scenarios and the significance of the frequency of data collection for accurate predictive modelling.