EPANET Input Files of New York tunnels and Pacific City used in a metamodel-based optimization study

Metamodels have proven be very useful when it comes to reducing the computational requirements of Evolutionary Algorithm-based optimization by acting as quick-solving surrogates for slow-solving fitness functions. The relationship between metamodel scope and objective function varies between applications, that is, in some cases the metamodel acts as a surrogate for the whole fitness function, whereas in other cases it replaces only a component of the fitness function. This paper presents a formalized qualitative process to evaluate a fitness function to determine the most suitable metamodel scope so as to increase the likelihood of calibrating a high-fidelity metamodel and hence obtain good optimization results in a reasonable amount of time. The process is applied to the risk-based optimization of water distribution systems; a very computationally-intensive problem for real-world systems. The process is validated with a simple case study (modified New York Tunnels) and the power of metamodelling is demonstrated on a real-world case study (Pacific City) with a computational speed-up of several orders of magnitude.

Seawater carbonate chemistry and survival, impairment of three phytoplankton species in a laboratory experiment

Sodium hypochlorite (NaOCl) is widely used to disinfect seawater in power plant cooling systems in order to reduce biofouling, and in ballast water treatment systems to prevent transport of exotic marine species. While the toxicity of NaOCl is expected to increase by ongoing ocean acidification, and many experimental studies have shown how algal calcification, photosynthesis and growth respond to ocean acidification, no studies have investigated the relationship between NaOCl toxicity and increased CO2. Therefore, we investigated whether the impacts of NaOCl on survival, chlorophyll a (Chl-a), and effective quantum yield in three marine phytoplankton belonging to different taxonomic classes are increased under high CO2 levels. Our results show that all biological parameters of the three species decreased under increasing NaOCl concentration, but increasing CO2 concentration alone (from 450 to 715 µatm) had no effect on any of these parameters in the organisms. However, due to the synergistic effects between NaOCl and CO2, the survival and Chl-a content in two of the species, Thalassiosira eccentrica and Heterosigma akashiwo, were significantly reduced under high CO2 when NaOCl was also elevated. The results show that combined exposure to high CO2 and NaOCl results in increasing toxicity of NaOCl in some marine phytoplankton. Consequently, greater caution with use of NaOCl will be required, as its use is widespread in coastal waters.

Coastal Urban Flood Resislience versus Climate Change

Processes of founding and expanding cities in coastal areas have undergone great changes over time driven by environmental conditions. Coastal settlements looked for places above flood levels and away from swamps and other wetlands whenever possible. As populations grew, cities were extending trying to avoid low and wet lands. No city has been able to limit its growth. The risk of flooding can never be eliminated, but only reduced to the extent possible. Flooding of coastal areas is today dramatically attributed to eustasic sea level rise caused by global climate change. This can be inaccurate. Current climate change is generating an average sea level upward trend, but other regional and local factors result in this trend being accentuated in some places or attenuated, and even reversed, in others. Then, the intensity and frequency of coastal flooding around the planet, although not so much as a unique result of this general eustasic elevation, but rather of the superposition of marine and crustal dynamic elements, the former also climate-related, which give rise to a temporary raising in average sea level in the short term. Since the Little Ice Age the planet has been suffering a global warming change leading to sea level rise. The idea of being too obeying to anthropogenic factors may be attributed to Arrhenius (1896), though it is of much later highlight after the sixties of the last century. Never before, the human factor had been able of such an influence on climate. However, other types of changes in sea levels became apparent, resulting from vertical movements of the crust, modifications of sea basins due to continents fracturing, drifting and coming together, or to different types of climate patterns. Coastal zones are then doubly susceptible to floods. Precipitation immediately triggers pluvial flooding. If it continues upland or when snow and glaciers melt eventually fluvial flooding can occur. The urban development presence represents modifying factors. Additional interference is caused by river and waste water drainage systems. Climate also influences sea levels in coastal areas, where tides as well as the structure and dynamic of the geoid and its crust come into play. From the sea, waters can flood and break or push back berms and other coastline borders. The sea level, controlling the mouth of the main channel of the basin's drainage system, is ultimately what governs flood levels. A temporary rise in sea level acts as a dam at the mouth. Even in absence of that global change, so, floods are likely going to increase in many urban coastal areas. Some kind of innovative methodologies and practices should be needed to get more flood resilience cities