Quantifying the fragility of coral reefs to hurricane impacts: a case study of the Florida Keys and Puerto Rico

Ecosystems like coral reefs mitigate rising coastal flood risks, but investments into their conservation remain low relative to the investments into engineered risk-mitigation structures. One reason is that quantifying the risk-reduction benefits of coral reefs requires an estimate of their fragility to severe stresses. Engineered structures typically have associated fragility functions which predict the probability of exceeding a damage state with the increasing loading intensity imposed by a stressor, like a hurricane. Here, we propose a preliminary framework for capturing the fragility of coral reefs towards hurricanes in an analogous way to that of an engineered structure. We base our framework on Disturbance Response Monitoring data collected in the Florida Keys and Puerto Rico following hurricanes Irma and Maria. We first establish a qualitatively consistent correlation between hurricane impacts and coral mortality rates using two surveys of coral health. We focus specifically on stony coral mortality as a metric for reef damage, simplifying the effect of coral morphology into a single quantitative index at the site scale. To quantify the loading intensity of a hurricane, we propose a Hurricane Wind Exposure Time that captures spatial variations in the exposure of different coral reef sites to hurricane force winds. We ultimately derive a simple empirical fragility function for the Florida Keys and Puerto Rico to support side-by-side comparisons of the cost-effectiveness of a coral reef and engineered solutions to flood risk reduction in these regions

Development of efficient designs of cooking systems. I. Experimental

In the conventional cooking practice, where a pot or a pan is directly placed on a flame, the thermal energy efficiency is in the range of 10-25%. It was thought desirable to increase this efficiency up to 60% or more. The cooking systems can be of various sizes. In the developing world (85% of the worlds population), open pan cooking is largely still practiced at the family level (4-10 people) or at the community level (50-2000 people or more). The latter requirement is encountered in schools, homes for senior citizens, jails, social and/or religious centers (temples, mosques, churches), social and/or educational functions (conferences, marriages, celebrations, etc.), remand homes, etc. For these different types of final application, in the present work, cooking systems have been developed. A systematic work has has been reported regarding the effect of several parameters on thermal efficiency. The parameters include the cooker size, number of pots, size and aspect ratio of the pots, heat flux, flame size, flux-time relationship, insulating alternatives, etc. Local and global optima of the parameters have been obtained, resulting in thermal efficiency of about 70%. © 2011 American Chemical Society

Development of efficient designs of cooking systems. II. Computational fluid dynamics and optimization

Sections 2-6 of Part I were devoted to the analysis of heat transfer characteristics of cookers. In all the experiments, only water was employed as a working medium. Now, we extend such an analysis to the actual cooking process in order to arrive at an improved cooking device. The major strategies for the optimization of energy utilization is to design appropriate insulation that has been obtained by two cover vessels. In order to select an air gap, the flow and temperature patterns in the air gap have been extensively analyzed using computational fluid dynamics (CFD). The flow pattern and heat transfer in cooking pots have also been analyzed by CFD. This has enabled us to design suitable internals for minimizing the stratification of temperature. The understanding of fluid mechanics has also given basis for selection of heat flux, gap between burner tip and cooker bottom, and temperature of flue gases leaving the cooker. Chemical engineering principles have been used for modeling and optimization. Kinetics have been obtained in batch cookers. The knowledge of kinetics, thermal mixing, axial mixing, and optimum selection of insulation have been employed for the development of continuous cookers. The continuous mode of operation also helps in saving of energy. Systematic data have been collected for the design and scale up of continuous cookers. © 2011 American Chemical Society