Coastal urban development incorporates a wide range of development activities that are taking place as a result of the water element existing in the fabric of the city. This element may have different forms (i.e. a bay, a river, or a brook) but in almost all cases the surrounding area constitutes what maybe considered as the heart of the city. Every city that incorporates the water-element in its fabric is confronted with the fundamental requirement of developing policies for driving development in the surrounding area, while balancing between: a) economic growth, b) protection of the environmental, and c) safeguarding social cohesion. This requirement is tightly connected with the concept of Urban Resilience, which is the capacity of individuals, communities, businesses and systems within a city to survive, adapt and grow no matter what chronic stresses and acute shocks they experience. In developing policies that add value to the resilience of a city, we shift the existing paradigm of policy making, which is largely based on intuition, towards an evidence-driven approach enabled by big data. Our attention is placed on policies related to the water element. Our basis is the sensing infrastructures installed in the cities offering demographic data, statistical information, sensor readings and user contributed content forming the big data layer. Methods for big data analytics are used to measure the economic activity, assess the environmental impact and evaluate the social consequences. The extracted pieces of evidence are used to inform, advice, monitor, evaluate and revise the decisions made by policy planners. Finally, effective policies are developed dealing with: a) the economic and urban development of Thermaikos Bay, Thessaloniki, b) the transformation of Düden Brook into a recreation and park area, Antalya, c) the development of a Storm Water Plan, Antwerp, and d) the review of the Country Development Plan in the River Lee territory, City of Cork.