Application of Landsat-7 satellite data and a DEM for the quantification of thermokarst-affected terrain types in the periglacial Lena-Anabar coastal lowland

Extensive parts of Arctic permafrost-dominated lowlands were affected by large-scale permafrost degradation, mainly through Holocene thermokarst activity. The effect of thermokarst is nowadays observed in most periglacial lowlands of the Arctic. Since permafrost degradation is a consequence as well as a signifi cant factor of global climate change, it is necessary to develop effi cient methods for the quantifi cation of its past and current magnitude. We developed a procedure for the quantifi cation of periglacial lowland terrain types with a focus on degradation features and applied it to the Cape Mamontov Klyk area in the western Laptev Sea region. Our terrain classifi cation approach was based on a combination of geospatial datasets, including a supervised maximum likelihood classifi cation applied to Landsat-7 ETM+ data and digital elevation data. Thirteen fi nal terrain surface classes were extracted and subsequently characterized in terms of relevance to thermokarst and degradation of ice-rich deposits. 78 % of the investigated area was estimated to be affected by permafrost degradation. The overall classifi cation accuracy was 79 %. Thermokarst did not develop evenly on the coastal plain, as indicated by the increasingly dense coverage of thermokarst-related areas from south to north. This regionally focused procedure can be extended to other areas to provide the highly detailed periglacial terrain mapping capabilities currently lacking in global-scale permafrost datasets

On hybrid model predictive control of sewer networks

Real-time control (RTC) of sewer-network systems plays an important role in meeting increasingly restrictive environmental regulations to reduce release of untreated wastewater to the environment. This chapter presents the application of hybrid model predictive control (HMPC) on sewer systems. It is known from the literature that HMPC has a computational complexity growing exponentially with the size of the system to be controlled. However, the average solution time of modern mixed integer program (MIP) solvers is often much better than the predicted worst-case-solution time. The problem is to know when the worst-case computational complexity appears. In addition to presenting the application, a secondary aim of the chapter is to discuss the limits of applicability due to real-time constraints on computation time when HMPC is applied on large-scale systems such as sewer networks. By using a case study of a portion of the Barcelona sewer system, it is demonstrated how the computational complexity of HMPC appears for certain state and disturbance combinations