1 Flood risk insurance: the Blockchain approach to a Bayesian adaptive design of the contract. Authors: Augusto Bellieri dei Belliera 1 , Marcello Galeotti 1 , Andrea Jonathan Pagano 2 , Giovanni Rabitti 3 , Francesco Romagnoli 2 , Emanuele Vannucci 4 1 University of Florence 2 Riga Technical University 3 Bocconi University, Milan 4 University of Pisa Abstract Informatics tools underlying cryptocurrencies markets, the so-called Blockchain, is raising up a lot of interest for applications in a wide range of fields. The key function of its use is to collect reliable information that could be used for a dy- namic updating of contracts, that is one of the main opportunity given by smart contracting, with an adequate support of law’s context in which such contracts are merged, that is one of the main issue to be developed for the full functioning of this kind of innovative business model. Blockchain and the connected smart contracting, seem very interesting even for insurance business, in particular for the bayesian adaptive approach which is a classic issue of actuarial science, based on the updating of premium evaluation using the collection of new information of risks phenomena. The new opportunity of collecting offered by the so-called big data even for classic insurance risks as for example, health, driving, climate and seismic events, together with the validating role of Blockchain approach, seem to be the perfect scenario for a massive use of smart contracting in insur- ance business. In this paper we describe the scheme of a flood risk insurance, the bayesian adaptive design of the contract, using Blockchain to validate both new data of risk phenomenon and the effect of mitigation of the faced risk due to infrastructural works. Keywords: Blockchain, smart contracts, flood insurance, bayesian infer- ence. Introduction The insurance sector, among many others, has an increasing interest for the application of blockchain technology, introduced by the milestone paper by the inventor Nakamoto [1], to its business, as shown by many documents of main insurance groups (let see [2], [3]) and consultancy firms ([4],[5],[6],[7]) and we have arrived to the creation, in 2016, of the B3i, the first blockchain-centered in- surance consortium (as described in [8]). The key point for the use of blockchain for insurance business is the feasibility of smart contracts in this sector and the answer seems to be positive almost for the so-called instantaneous insurance, i.e. contracts with short duration which imply an automatism in issuing and in pay- ing the eventual benefit settled in the contract as, for example, the flight delay insurance proposed by AXA, called Fizzy, completely developed on a blockchain platform.