Understanding how well critical source areas of water or sediment are connected to receiving surface waters, is an essential step towards improvement of land management. For this, it is important to quantify connectivity beyond the conceptual and proportional evaluation that most studies use connectivity for. Most studies measure only the potential of a landscape to allow connectivity to occur; or the connectivity that occurs at a given moment. This fact shows the two opportunities that will make it possible to monitor connectivity: assess the potential connectivity and the water and sediment fluxes through those landscapes. These components finally may result in the desired knowledge on the connectivity of the research area. In this chapter, we identify three spatial levels of connectivity: soil, hillslopes and catchments. In addition, to be able to measure and monitor connectivity the stocks and flow within every spatial level is introduced to allow for the identification of available techniques to actually assess connectivity at the given scale. The chapter ends with a set of key questions that need answering to make measuring connectivity on different scales reliable and useful.

This chapter discusses what is meant by connectivity in fluvial systems and how the connectivity approach differs from preceding research, the way in which it increases understanding of fluvial processes, and how knowledge of mechanisms and dynamics of processes fits into this framework. The focus is on longitudinal connectivity through river systems, mainly in large catchments and river channels and much of the attention is on sediment connectivity. The application of connectivity indices and graph theory are exemplified and the patterns, distributions and controls produced by connectivity analysis are demonstrated. Lateral connectivity is important in relation to the link of channels to floodplains and in maintaining functioning of wetlands. Recent developments of techniques and models have allowed additional factors to be incorporated and controls on connectivity of fluvial processes to be identified. The use of connectivity analysis as a framework is highly beneficial in management of fluvial systems and facilitates targeting of hotspots of sediment accumulation or depletion.

In this chapter, we review approaches to model climate-related migration including the multiple goals of modeling efforts and why modeling climate-related migration is of interest to researchers, commonly used sources of climate and migration data and data-related challenges, and various modeling methods used. The chapter is not meant to be an exhaustive inventory of approaches to modeling climate-related migration, but rather is intended to present the reader with an overview of the most common approaches and possible pitfalls associated with those approaches. We end the chapter with a discussion of some of the future directions and opportunities for data and modeling of climate-related migration.

Modelling connectivity is a three-stage process. Foremost, is the conceptualization of the connectivity problem. Two end-members of connectivity may be defined. The first considers connectivity to be an emergent property of a system. The second imposes on the system a specific definition of what connectivity is. The former conceptualisation is useful for applications where feedbacks between functional and structural connectivity occur over a shorter timescale than the duration of the model application, and for developing understanding based on model development and application. The latter is better used where prediction or application of the model results is required. It is further necessary to answer questions about space and time scales of the application and data available to support it. Once the basic units of spatial scale can be defined, development of the model can move on to considering what data are most appropriate at that scale, and how to collect them. In the final stage, different model structures that reflect the emerging and parameterized connectivity end-members are considered. The chapter gives examples of these stages with reference to modelling of water flows and consequent erosion.

Wind transports particles by creep, saltation and suspension, of which saltation dominates and is responsible for aeolian landforms. Transported particles generally must go around objects, so that the connectivity defined by the spatial distribution of objects on the surface controls sediment transport. Four spatial and temporal scales of sediment transport are defined. At gap to patch scales, vegetation typically defines the structural connectivity. Vegetation remains important at landscape to basin scales but geomorphic features also contribute to defining transport corridors, or structural connectivity, at the coarsest scale. Patterns of aeolian transport through time are essentially constrained by structural connectivity at multiple, embedded scales. Functional connectivity is not well developed in the aeolian realm and, because particles do not travel more than one or two saltation hops during a single event, functional connectivity is only a relevant concept at the finest spatial scales. Aeolian transport must be approached from the multiple spatial (gap to basin) and temporal (single event to longer periods) scales that define structural and functional connectivity.

Periglacial regions and processes are particularly affected by contemporary climate change. These changes modify sediment connectivity and flux significantly. Connectivity is dynamic, evolving in response to the sediment transport processes it itself induces; and connection and disconnection have to be viewed as relative and multi-variate concepts. For most of the time, a landscape is functionally disconnected; sediment does not move. When it does move, at more connected locations it is more likely to move further downstream. However, because such sediment flux (i.e., functional connectivity) may cause landscape changes that in turn change connection, this static structural representations of connectivity also need to be considered as non-stationary. We illustrate these points using examples from the Arolla and Ferpecle-Mont Miné Valleys, located in the Val d’Hérens of Canton Valais, in Switzerland. These examples: (1) illustrate the spatial variability of the functional connectivity; (2) show how structural connectivity interacts with the processes that drive sediment flux; and (3) demonstrate the ways in which sediment flux can lead to evolution of structural connectivity.

Farming has modified the natural dynamic of soil erosion/redistribution in significant parts of landscapes, triggering high rates of soil loss and accelerating sediment connectivity. This chapter provides a review of sediment connectivity in grassland, herbaceous and woody crops from knowledge to management. The first section explores the extension of farmland at a global scale and the process of agricultural land expansion. Regarding herbaceous crops, the second section highlights the importance of cropping intensity (one or two crops per year), water supply (rainfed or irrigated), and crop rotation on the sediment-connectivity magnitude. In the section of woody crops, studies done in vineyards, olive groves and citrus orchards describe the processes of sediment connectivity with and without soil conservation practices (e.g., cover crops). The section of sediment connectivity in grasslands includes examples in alpine hillsides, valley bottom and lakes, emphasizing their role as sediment-trapping features. The last section deals with sediment dis-connectivity in farmland due to soil erosion control practices and governmental programs, with examples from Europe and China.

This chapter reviews how climate change is projected to affect the frequency, severity and/or spatial distribution of tropical cyclones, severe storms that generate tornadoes, and floods; the factors that influence people’s exposure and vulnerability to such events; adaptation options for reducing displacement risks; and, common characteristics of migration and displacement across all categories of extreme weather events. We then focus on specific types of extreme weather and provide more detailed analyses and case studies of migration and displacement events associated with tropical cyclones, tornadoes, and floods.

A number of indices has been proposed to assess hydrological or sediment connectivity. These indices operate at different spatial scales, address different types of connectivity (hillslope-channel vs. longitudinal connectivity), are based on different spatial units (raster cell, landform, channel reach, sub-/catchment) and approaches (geomorphological mapping, digital elevation models, network analysis). Temporal constraints for the application of indices exist as connectivity depends on the magnitude of hydrometeorological forcing, and is subject to changes in landscape properties. Connectivity indices are based on variables and assumptions with respect to space and time. We review existing indices of different characteristics (raster, effective catchment area, networks) together with examples, and distinguish two types of their application: descriptive applications in which indices are used to describe spatial patterns of water and sediment (coupled and decoupled) pathways for a point or period of time; and as predictors of connectivity and its consequences (e.g., sediment transfer, sensitivity to change). Opportunities and challenges for research in connectivity indices are discussed.

The concept of connectivity appeared in several disciplines in the 1950s and 1960s, but did not enter geomorphology until the 1980s. The concept has led to profound insights into the behaviour of systems, and has had significant applications in management. Connectivity may be defined as a structured set of relationships between spatially and/or temporally distinct entities), or as the degree to which a system facilitates (or impedes) the movement of matter and energy through itself. The former definition focuses on the structure of the system, and the latter on the functioning of it. The two definitions give rise to the separate concepts of structural and functional connectivity. A fundamental difference between structural and functional connectivity lies in the fact that, whereas the former can be relatively easily measured, and a variety of tools exists to do so, the latter tends to be inferred from system behaviour, so that measurement is somewhat indirect. Notwithstanding the compelling arguments in favour of studying connectivity, the ability to apply the ideas of connectivity science in any discipline requires a number of challenges to be addressed.

Vegetation cover in drylands tends to be sparse and organised as a mosaic of patches with high biomass interspersed within a bare soil component. Water availability and vegetation are tightly coupled in these environments, where landscape function is determined by hydrologic and sediment connectivity. In this chapter, we analyse and synthesise previous studies describing how understanding, measuring and modifying connectivity can be used to guide the design of management strategies aiming at improving landscape resilience. We describe how drylands are very sensitive to both water and wind erosion, which have the potential to increase connectivity beyond tipping points at which the system transitions abruptly to a degraded state that may be irreversible. We discuss methods for the identification of early warning indicators of transition to degraded states, which could be used as a preventive management tool. We also describe existing strategies and approaches to reduce connectivity at different spatial scales as a way of managing degraded landscapes.