Papers by Dimitris Fotakis
A genetic algorithm and a simulated annealing approach is presented for the guidance of a cellula... more A genetic algorithm and a simulated annealing approach is presented for the guidance of a cellular automaton toward optimal configurations. The algorithm is applied to a problem of groundwater allocation in a rectangular area consisting of adjacent land blocks and modeled as a cellular automaton. The new algorithm is compared to a more conventional genetic algorithm and its efficiency is
Diversity
Plants know no political borders and some of them are restricted to small geographical territorie... more Plants know no political borders and some of them are restricted to small geographical territories of different countries in which they are endemic. In this study, we prioritized plants (PPs) of the cross-border area of Greece and the Republic of North Macedonia that are already threatened or nearly so (PPA), those which occur exclusively on either side of borderline and/or nearby countries (PPB), or those which are uncommon and rare in this region (PPC) with the aim to document in-situ the species-specific risks-threats; offer ex-situ conservation for them as a back-up solution for future re-introductions and sustainable exploitation; and raise public awareness and alertness about the importance of local biodiversity. In the framework of the project Conse-pp, 20 botanical expeditions were performed in 75 selected areas to collect samples and suitable propagation material from 130 PPs (147 accession numbers), also recording all types of threats-identified in-situ for each of them. N...
Hydrological Sciences Journal, 2018
Ten notable meteorological drought indices were compared on tracking the effect of drought on str... more Ten notable meteorological drought indices were compared on tracking the effect of drought on streamflow. A 730-month dataset of precipitation, temperature and evapotranspiration for 88 catchments in Oregon, USA, representing pristine conditions, was used to compute the drought indices. These indices were correlated with the monthly streamflow datasets of the minimum, maximum and mean discharge, and the discharge monthly fluctuation; it was revealed that the 3-month Z-score drought index (Z3) has the best association with the four streamflow variables. The Mann-Kendall trend detection test applied to the latter index time series mainly highlighted a downward trend in the autumn and winter drought magnitude (DM) and an upward trend in the spring and summer DM (p = 0.05). Finally, the Pettitt test indicated an abrupt decline in the annual and autumn DM, which began in 1984 and 1986, respectively.
International Journal of Information and Decision Sciences, 2015
A survey was carried out during a workshop of the Greek National Forest Governance Council to ide... more A survey was carried out during a workshop of the Greek National Forest Governance Council to identify the strengths, weaknesses, opportunities and threats for sustainable forest management assessment in Greece. The National Forest Governance Council was established within the frame of the INFORM project financed through LIFE. Its main role is to support the development process of a knowledge base for development of national forest policy on sustainable forest management assessment and monitoring. This paper presents the important internal and external factors for sustainable forest management assessment identified in the four groups: strengths, weaknesses, opportunities and threats, for the forests of Eastern Macedonia and Thrace region, in Northern Greece. It also discusses the strategies for this area resulting in a good fit between the internal and external factors. SWOT provides a basic frame within which an analysis of the strategic forest planning environment towards sustainable forest management assessment can be performed.
Land use planning is a significant component of environmental management. A characteristic proble... more Land use planning is a significant component of environmental management. A characteristic problem arising in such planning consists in dividing a given area into land blocks for the purpose of optimally assigning a land use to each one of them and distributing resources or commodities over the resulting spatial arrangement. A specific instance of the above generic problem is the allocation of water to the land blocks. Both an extraction and a transport cost are involved in this case, thus resulting in a nonlinear optimization problem. This problem has been treated by the authors by means of genetic algorithms and cellular automata. The present paper gives an alternative approach based on stochastic evolution and on simulated evolution. These are evolutionary methods of the literature employed for the solution of classical combinatorial optimization methods, such as the graph partition and the travelling salesman problem. These methods are adapted for the solution of the water alloc...
Cellular Automata - Simplicity Behind Complexity, 2011
Forest Policy and Economics, 2012
A spatial operator for genetic algorithms is introduced herein, in order to improve their efficie... more A spatial operator for genetic algorithms is introduced herein, in order to improve their efficiency for multiobjective spatial forest planning. Constrained NSGA-II is used as a standard genetic algorithm for the integration and the evaluation of the proposed methodology. A typical harvest scheduling problem is examined with two objectives: a) maximization of timber volume and b) minimization of sediment levels. Two constraints are imposed: a) minimum timber yield and b) even-flows. The proposed algorithm (Spatial NSGA), gives better results for both the constrained and the unconstrained problem. Moreover, it achieves old forest compactness, although it is neither a separate objective nor a constraint, but it renders compactness as an emergent result. The purpose of the suggested approach is to support forestry decision-making by generating a set of optimal management alternatives. The implementation of the method produced a Pareto front consisting of non-dominating solutions and showing the tradeoffs between timber harvest and sediment levels in water runoff. The present approach offers potential applications to a wide spectrum of spatial planning problems beyond the one examined in this paper.
Forest Policy and Economics, 2012
A spatial operator for genetic algorithms is introduced herein, in order to improve their efficie... more A spatial operator for genetic algorithms is introduced herein, in order to improve their efficiency for multiobjective spatial forest planning. Constrained NSGA-II is used as a standard genetic algorithm for the integration and the evaluation of the proposed methodology. A typical harvest scheduling problem is examined with two objectives: a) maximization of timber volume and b) minimization of sediment levels. Two constraints are imposed: a) minimum timber yield and b) even-flows. The proposed algorithm (Spatial NSGA), gives better results for both the constrained and the unconstrained problem. Moreover, it achieves old forest compactness, although it is neither a separate objective nor a constraint, but it renders compactness as an emergent result. The purpose of the suggested approach is to support forestry decision-making by generating a set of optimal management alternatives. The implementation of the method produced a Pareto front consisting of non-dominating solutions and showing the tradeoffs between timber harvest and sediment levels in water runoff. The present approach offers potential applications to a wide spectrum of spatial planning problems beyond the one examined in this paper.
A genetic algorithm and a simulated annealing approach is presented for the guidance of a cellula... more A genetic algorithm and a simulated annealing approach is presented for the guidance of a cellular automaton toward optimal configurations. The algorithm is applied to a problem of groundwater allocation in a rectangular area consisting of adjacent land blocks and modeled as a cellular automaton. The new algorithm is compared to a more conventional genetic algorithm and its efficiency is clearly demonstrated. Also, comparison is made to a simulated annealing scheme. Finally, the proposed genetic algorithm is combined with simulated annealing to yield a new hybrid. The presented cell - based algorithm is different from related algorithms of the literature, as it relies on local interactions among land blocks. Moreover, it offers a framework for application to more general and detailed problems.
Fresenius Environmental Bulletin
Protecting the Nestos/Mesta River is essential because of it encompasses many Natura 2000 sites a... more Protecting the Nestos/Mesta River is essential because of it encompasses many Natura 2000 sites and a RAMSAR wetland. To develop cost-effective management plans the condition of the riparian areas need to be examined. Riparian areas have many ecological functions and can influence the functionality of the adjacent streams and rivers. Using G.I.S. tools the land-use/vegetation cover proportion was estimated at 10, 20, 30, 60, 90 and 120 meter buffers along the streams and rivers in the largest Greek sub-basin of the Nestos River. These estimates were for the different stream orders and for the mountainous and flat portion of the sub-basin. The riparian areas of all the stream orders in the mountainous portion had the largest percentage in woody vegetation and grasslands. In the flat portion of the basin, high order streams had the largest percentage of their riparian areas in natural vegetation whereas the low order streams and the irrigation canals had the largest percentage in agri...
Ecological Informatics, 2015
ABSTRACT The spatial and temporal aspects of forest planning are taken into consideration in this... more ABSTRACT The spatial and temporal aspects of forest planning are taken into consideration in this paper in a forest harvest scheduling problem that is treated with the following two conflicting objectives: (a) maximization of timber volume and (b) minimization of sedimentation. Two realistic constraints are considered: (a) lower bound for timber yield and (b) even flows between management periods. An optimization algorithm based on self-organization is applied through a spatial transition rule. The optimization procedure does not use weighted sum objective functions but it produces a Pareto front. The proposed algorithm manages to overcome the local character of the transition rule and to achieve global, emergent results, such as compactness.
Water, 2014
Watershed simulation software used for operational purposes must possess both dependability of re... more Watershed simulation software used for operational purposes must possess both dependability of results and flexibility in parameter selection and testing. The UBC watershed model (UBCWM) contains a wide spectrum of parameters expressing meteorological, geological, as well as ecological watershed characteristics. The hydrological model was coupled to the MapInfo GIS and the software created was named Watershed Mapper (WM). WM is endowed with several features permitting operational utilization. These include input data and basin geometry visualization, land use/cover and soil simulation, exporting of statistical results and thematic maps and interactive variation of disputed parameters. For the application of WM two hypothetical scenarios of forest fires were examined in a study watershed. Four major rainfall events were selected from 12-year daily precipitation data and the corresponding peak flows were estimated for the base line data and hypothetical scenarios. A significant increase was observed as an impact of forest fires on peak flows. Due to its flexibility the combined tool described herein may be utilized in modeling long-term hydrological changes in the context of unsteady hydrological analyses.
Water Resources Management, 2012
During the last decades, a progressive decrease of water level in shallow Mediterranean lakes was... more During the last decades, a progressive decrease of water level in shallow Mediterranean lakes was recorded. This contribution tried to identify whether the rapid decrease of the Lake Doiran (N. Greece) water level was associated with drought phenomena. Drought characteristics over the study area were revealed by employing the Standardized Precipitation Index (SPI) in different time scales. Negative trends of the SPI drought index were recognized by using the Mann-Kendall non parametric test, which suggested that drought conditions were intensified through time. The impact of the intense drought phenomena to the lake's water level became evident by employing the Pearson correlation coefficient. A year ahead forecast of future drought conditions was achieved by training a hybrid ARIMA/ANN model. The predicted results indicated that mild drought conditions should be anticipated in the future and the water level would further drop as well.
Forest Policy and Economics, 2012
A spatial operator for genetic algorithms is introduced herein, in order to improve their efficie... more A spatial operator for genetic algorithms is introduced herein, in order to improve their efficiency for multiobjective spatial forest planning. Constrained NSGA-II is used as a standard genetic algorithm for the integration and the evaluation of the proposed methodology. A typical harvest scheduling problem is examined with two objectives: a) maximization of timber volume and b) minimization of sediment levels. Two constraints are imposed: a) minimum timber yield and b) even-flows. The proposed algorithm (Spatial NSGA), gives better results for both the constrained and the unconstrained problem. Moreover, it achieves old forest compactness, although it is neither a separate objective nor a constraint, but it renders compactness as an emergent result. The purpose of the suggested approach is to support forestry decision-making by generating a set of optimal management alternatives. The implementation of the method produced a Pareto front consisting of non-dominating solutions and showing the tradeoffs between timber harvest and sediment levels in water runoff. The present approach offers potential applications to a wide spectrum of spatial planning problems beyond the one examined in this paper.
Applied Mathematics and Computation, 2012
Spatial planning is an important and complex activity. It includes land use planning and resource... more Spatial planning is an important and complex activity. It includes land use planning and resource allocation as basic components. An abundance of papers can be found in the literature related to each one of these two aspects separately. On the contrary, a much smaller number of research reports deal with both aspects simultaneously. This paper presents an innovative evolutionary algorithm for treating combined land use planning and resource allocation problems. The new algorithm performs optimization on a cellular automaton domain, applying suitable transition rules on the individual neighbourhoods. The optimization process is multi-objective, based on non-domination criteria and selforganizing. It produces a Pareto front thus offering an advantage to the decision maker, in comparison to methods based on weighted-sum objective functions. Moreover, the present multi-objective self-organizing algorithm (MOSOA) can handle both local and global spatial constraints. A combined land use and water allocation problem is treated, in order to illustrate the cellular automaton optimization approach. Water is allocated after pumping from an aquifer, thus contributing a nonlinearity to the objective function. The problem is bi-objective aiming at (a) the minimization of soil and groundwater pollution and (b) the maximization of economic profit. An ecological and a socioeconomic constraint are imposed: (a) Groundwater levels at selected places are kept above prescribed thresholds. (b) Land use quota is predefined. MOSOA is compared to a standard multi-objective genetic algorithm and is shown to yield better results both with respect to the Pareto front and to the degree of compactness. The latter is a highly desirable feature of a land use pattern. In the land use literature, compactness is part of the objective function or of the constraints. In contrast, the present approach renders compactness as an emergent result.
Annals of Operations Research, 2012
A general framework for a combined land use and water management is described. An optimization pr... more A general framework for a combined land use and water management is described. An optimization problem is formulated that combines combinatorial and spatial characteristics. The aim of the planning is to maximize economic benefit, while minimizing water extraction and transportation cost under ecological constraints. A genetic algorithm is employed endowed with a new neighborhood operator. This operator acts on a local level, but it produces global results. Although the computational scheme does not include compactness as a separate objective, compact patterns are produced as emergent results. The algorithm is tested on a fictive area represented as a grid with 15 × 15 land blocks and, also, on a real-world case study.
Conference Presentations by Dimitris Fotakis
Groundwater allocation is a fundamental planning activity within the more general domains of land... more Groundwater allocation is a fundamental planning activity within the more general domains of land use planning and environmental management. The overall problem is formulated by assigning land uses to a number of land blocks belonging to a certain area and then optimally distributing resources or commodities over the blocks. In particular, groundwater as such a resource, gives rise to interesting and challenging optimization problems, involving simultaneously allocation as well as extraction. This paper presents an integrated allocation and extraction problem, thus giving a new, unified treatment of the two management activities. As in previous publications of the authors, the concept of cellular automaton is utilized, combined with evolutionary methods that guide the cellular structure to optimal arrangements. Two less well-known evolutionary approaches are employed here, namely stochastic and simulated evolution. These methods have not appeared so far in the water resources literature. Moreover, multi-objective versions of these methods are presented, extending previous work of the authors. The optimal solutions obtained are discussed and compared to other competitive methods such as simulated annealing, as well as to a standard multi-objective genetic algorithm of the literature.
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Papers by Dimitris Fotakis
Conference Presentations by Dimitris Fotakis