Protective measures against torrential floods and lowlands’ floods have been set up since the 19th century in mountainous areas. To help decide on maintenance of numerous existing structures, a better understanding of their objectives and technical functions is needed. Nevertheless, that remains tricky in torrent management context, due to several changes for more than 150 years, either in terms of natural torrential risk (e.g. land-use changes), scientific understanding of complex phenomena (e.g. hillslope-streambed coupling), understanding of protective actions (e.g. influence on the sediment transport), laws and regulations (e.g. increasing of multi-issues problems), and management organization. An archive analysis was done to bridge this gap. Pioneering books of the late 19th century have been reviewed to sum up local and regional objectives of protective measures, but also their technical functions on torrential processes. We recall the first RTM laws and their implementation conditions. An analysis of laws, regulations and public management evolutions helps to understand risk management changes, influencing current maintenance decisions. We finally synthesize the objectives and local technical functions of protective measures. We propose some elements to go towards a quantification of risk reduction even if it remains a key challenge.