Flood disturbance, recovery, and inter-flood incision on a large sand-bed river

Explosive volcanic eruptions are among the most significant natural disturbances to landscapes on Earth. The widespread and rapid influx of pyroclastic sediment, together with subsequent changes to topography and vegetation cover, drives markedly heightened runoff responses to rainfall and increased downstream water and sediment fluxes; principally by way of hazardous lahars. The nature and probability of lahar occurrence under given rainfall conditions evolves as the landscape responds and subsequently recovers following the disturbance. The relationship between varying sediment supply, rainfall patterns, vegetation cover and lahar activity is complex, and impedes forecasting efforts made in the interest of hazard and land use management. Thus, developing an improved understanding of how these systems evolve in response to volcanic eruptions is of high importance.Here we present SedCas_Volcano[MOU1]&#160;, a conceptual sediment cascade model, designed to simulate the first-order trends, such as magnitude-frequency distributions or seasonal patterns, in lahar activity and sediment transport. We use the Belham River Valley, Montserrat, as a case study. This small (~15km2) catchment has been repeatedly disturbed by five phases of volcanic activity at the Soufri&#232;re Hills Volcano since 1995. The multi-phase nature of this eruption, together with the varying nature and magnitude of disturbances throughout the eruption, has driven a complex disturbance-recovery cycle, which is further compounded by inter-annual climatic variations (e.g. ENSO). Lahars have occurred frequently in response to rainfall in the Belham River Valley, and their occurrence has evolved through the repeated disturbance-recovery cycle. This activity has resulted in significant net valley floor aggradation and widening, consequent burial and destruction of buildings and infrastructure, as well as coastal aggradation of up to ~250m. Within SedCas_Volcano, we account for evolving sediment supply, vegetation cover and rainfall, to simulate the lahar activity and channel change observed in the Belham River Valley since January 2001. Following this, we test the model under different hypothetical eruptive scenarios. [MOU2]&#160;Our goal is to assess the efficacy of such models for reproducing patterns of lahar activity and geomorphic change in river systems that are repeatedly disturbed by volcanic activity.

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Post-disturbance recovery of forest cover and tree height differ with management in Central Europe

Landscape Ecology ◽

10.1007/s10980-019-00921-9 ◽

2019 ◽

Vol 34 (12) ◽

pp. 2837-2850 ◽

Cited By ~ 5

Author(s):

Cornelius Senf ◽

Jörg Müller ◽

Rupert Seidl

Keyword(s):

Central Europe ◽

Forest Ecosystem ◽

Forest Structure ◽

Forest Ecosystems ◽

Tree Cover ◽

Managed Forests ◽

Central European ◽

Stand Height ◽

European Forest ◽

Disturbance Recovery

Abstract Context Recovery from disturbances is a prominent measure of forest ecosystem resilience, with swift recovery indicating resilient systems. The forest ecosystems of Central Europe have recently been affected by unprecedented levels of natural disturbance, yet our understanding of their ability to recover from disturbances is still limited. Objectives We here integrated satellite and airborne Lidar data to (i) quantify multi-decadal post-disturbance recovery of two indicators of forest structure, and (ii) compare the recovery trajectories of forest structure among managed and un-managed forests. Methods We developed satellite-based models predicting Lidar-derived estimates of tree cover and stand height at 30 m grain across a 3100 km2 landscape in the Bohemian Forest Ecosystem (Central Europe). We summarized the percentage of disturbed area that recovered to > 40% tree cover and > 5 m stand height and quantified the variability in both indicators over a 30-year period. The analyses were stratified by three management regimes (managed, protected, strictly protected) and two forest types (beech-dominated, spruce-dominated). Results We found that on average 84% of the disturbed area met our recovery threshold 30 years post-disturbance. The rate of recovery was slower in un-managed compared to managed forests. Variability in tree cover was more persistent over time in un-managed forests, while managed forests strongly converged after a few decades post-disturbance. Conclusion We conclude that current management facilitates the recovery of forest structure in Central European forest ecosystems. However, our results underline that forests recovered well from disturbances also in the absence of human intervention. Our analysis highlights the high resilience of Central European forest ecosystems to recent disturbances.

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Effects of Stochastic Flood Disturbance on Adult Wood Turtles, Glyptemys insculpta, in Massachusetts

The Canadian Field-Naturalist ◽

10.22621/cfn.v123i4.1000 ◽

2009 ◽

Vol 123 (4) ◽

pp. 313 ◽

Cited By ~ 5

Author(s):

Michael T. Jones ◽

Paul R. Sievert

Keyword(s):

Average Rate ◽

Population Connectivity ◽

Flood Frequency ◽

Flood Disturbance ◽

Franklin County ◽

Present Evidence ◽

Glyptemys Insculpta ◽

Riparian System ◽

Flood Intensity ◽

Wood Turtles

The homing ability of non-marine turtles has been studied in a variety of taxa, and many species appear to be capable of short-range homing on the scale of several hundred meters or a few kilometers following experimental displacement. However, the behavioral response of turtles following a naturally caused displacement has seldom been reported. In this paper, we describe the effect of displacement ranging from 1.4 to 16.8 km (average = 4.8 km) by severe floods in a stream system in Massachusetts. We radio-tracked 38 adult Wood Turtles (Glyptemys insculpta) at five separate sites in Franklin County, Massachusetts, for periods ranging from one to four activity seasons and documented the displacement of a total of 12 Wood Turtles during seven floods between 2004 and 2008. Based on the average rate of displacement per flood and annual flood frequency, we estimate that, during our study, floods displaced over 40% of this Wood Turtle subpopulation annually. We present evidence that displacement results in elevated mortality rates and that displaced Wood Turtles mate and nest in the year following displacement at rates well below average; on a longer time scale, however, displacement by flooding may be an important mechanism of population connectivity in some areas. We also present evidence that most Wood Turtles avoid stream segments with stream gradient steeper than 1%; this may in part reflect an adaptation to avoid severe floods. Regional models and empirical data from stream gages suggest that flood intensity may currently be on an increasing trend. Conversion of upland from forest and fields to impervious surfaces and hardening of upstream riverbanks may have exacerbated recent flooding and decreased the resiliency of the riparian system to increased precipitation.

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