A unified swelling potential index for expansive soils

Kariuki, Patrick Chege; Meer, Freek D. van der

doi:10.1016/s0013-7952(03)00159-5

Cited by 37 publications

(18 citation statements)

References 16 publications

(26 reference statements)

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“…Internal shrinkage and swelling of clay minerals such as smectites or vermiculites can cause soil shrinkage (Kariuki and van der Meer, 2004), which is driven by soil moisture changes. In temperate climate regions normal shrinkage is the most relevant mechanism, where volume reduction is approximately proportional to the water loss (Chertkov, 2000).…”

Section: Shrinking and Swelling Soils Overland Flow And Infiltrationmentioning

confidence: 99%

Threshold behaviour in hydrological systems as (human) geo-ecosystems: manifestations, controls, implications

Zehe¹,

Sivapalan

2009

Hydrol. Earth Syst. Sci.

196

139

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Abstract. In this paper we review threshold behaviour in environmental systems, which are often associated with the onset of floods, contamination and erosion events, and other degenerative processes. Key objectives of this review are to a) suggest indicators for detecting threshold behavior, b) discuss their implications for predictability, c) distinguish different forms of threshold behavior and their underlying controls, and d) hypothesise on possible reasons for why threshold behaviour might occur. Threshold behaviour involves a fast qualitative change of either a single process or the response of a system. For elementary phenomena this switch occurs when boundary conditions (e.g., energy inputs) or system states as expressed by dimensionless quantities (e.g. the Reynolds number) exceed threshold values. Mixing, water movement or depletion of thermodynamic gradients becomes much more efficient as a result. Intermittency is a very good indicator for detecting event scale threshold behavior in hydrological systems. Predictability of intermittent processes/system responses is inherently low for combinations of systems states and/or boundary conditions that push the system close to a threshold. Post hoc identification of "cause-effect relations" to explain when the system became critical is inherently difficult because of our limited ability to perform observations under controlled identical experimental conditions. In this review, we distinguish three forms of threshold behavior. The first one is threshold behavior at the Correspondence to: E. Zehe (e.zehe@bv.tum.de) process level that is controlled by the interplay of local soil characteristics and states, vegetation and the rainfall forcing. Overland flow formation, particle detachment and preferential flow are examples of this. The second form of threshold behaviour is the response of systems of intermediate complexity -e.g., catchment runoff response and sediment yield -governed by the redistribution of water and sediments in space and time. These are controlled by the topological architecture of the catchments that interacts with system states and the boundary conditions. Crossing the response thresholds means to establish connectedness of surface or subsurface flow paths to the catchment outlet. Subsurface stormflow in humid areas, overland flow and erosion in semi-arid and arid areas are examples, and explain that crossing local process thresholds is necessary but not sufficient to trigger a system response threshold. The third form of threshold behaviour involves changes in the "architecture" of human geoecosystems, which experience various disturbances. As a result substantial change in hydrological functioning of a system is induced, when the disturbances exceed the resilience of the geo-ecosystem. We present examples from savannah ecosystems, humid agricultural systems, mining activities affecting rainfall runoff in forested areas, badlands formation in Spain, and the restoration of the Upper Rhine river basin as examples of this phenomenon. This fun...

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Section: Shrinking and Swelling Soils Overland Flow And Infiltrationmentioning

confidence: 99%

Threshold behaviour in hydrological systems as (human) geo-ecosystems: manifestations, controls, implications

Zehe¹,

Sivapalan

2009

Hydrol. Earth Syst. Sci.

196

139

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“…Shrinkage and swelling of clay soils can lead to significant changes in the infiltrability and the soil volume and is usually a result of changes in soil moisture. Internal shrinkage and swelling of clay minerals such as smectites or vermiculites may influence shrinkage characteristics of soils or clay pastes [ Kariuki and van der Meer , 2004]. Especially the size and structure of the clay minerals determine the soil porosity [ Chertkov , 2000].…”

Section: Threshold Processes Study Sites and Datamentioning

confidence: 99%

Patterns of predictability in hydrological threshold systems

Zehe

Elsenbeer

Lindenmaier

et al. 2007

Water Resources Research

116

111

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Observations of hydrological response often exhibit considerable scatter that is difficult to interpret. In this paper, we examine runoff production of 53 sprinkling experiments on the water‐repellent soils in the southern Alps of Switzerland; simulated plot scale tracer transport in the macroporous soils at the Weiherbach site, Germany; and runoff generation data from the 2.3‐km2 Tannhausen catchment, Germany, that has cracking soils. The response at the three sites is highly dependent on the initial soil moisture state as a result of the threshold dynamics of the systems. A simple statistical model of threshold behavior is proposed to help interpret the scatter in the observations. Specifically, the model portrays how the inherent macrostate uncertainty of initial soil moisture translates into the scatter of the observed system response. The statistical model is then used to explore the asymptotic pattern of predictability when increasing the number of observations, which is normally not possible in a field study. Although the physical and chemical mechanisms of the processes at the three sites are different, the predictability patterns are remarkably similar. Predictability is smallest when the system state is close to the threshold and increases as the system state moves away from it. There is inherent uncertainty in the response data that is not measurement error but is related to the observability of the initial conditions.

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“…The use of the water content at À33 kPa matric water potential and COLE instead of more elaborate indicators of water holding capacity and shrink-swell potential (Thomas et al, 2000;Kariuki and van der Meer, 2004) in modeling, simplifies representation of the mechanistic shrink-swell processes. First, the laboratorydetermined water content associated with À33 kPa matric water potential would be used as the starting point for cracking as soil dries under field conditions.…”

Section: Introductionmentioning

confidence: 99%