Examinando por Autor "Sandi, Steven G."
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Ítem Acceso Abierto A Framework For The Ecogeomorphological Modelling Of The Macquarie Marshes, Australia(2014-12) Rodriguez, Jose F.; Seoane Salazar, Manuel; Sandi, Steven G.; Saco, Patricia M.; Riccardi, Gerardo A.; Saintilan, Neil; Wen, LiÍtem Acceso Abierto Calibration, validation and predictive capability of a wetland evolution model for subtropical estuaries.(2016-04) Rodriguez, Jose F.; Sandi, Steven G.; Saco, Patricia M.; Riccardi, Gerardo A.Ítem Acceso Abierto Coevolution of hydrodynamics, vegetation and channel evolution in wetlands of a semi-arid floodplain(EGU General Assembly 2015, 2015-04) Seoane, Manuel; Rodriguez, Jose F.; Sandi, Steven G.; Saco, Patricia M.; Riccardi, Gerardo A.; Saintilan, Neil; Wen, LiThe Macquarie Marshes are located in the semi-arid region in north western NSW, Australia, and constitute part of the northern Murray–Darling Basin. The Marshes are comprised of a system of permanent and semi-permanent marshes, swamps and lagoons interconnected by braided channels. The wetland complex serves as nesting place and habitat for many species of water birds, fish, frogs and crustaceans, and portions of the Marshes was listed as internationally important under the Ramsar Convention. Some of the wetlands have undergone degradation over the last four decades, which has been attributed to changes in flow management upstream of the marshes. Among the many characteristics that make this wetland system unique is the occurrence of channel breakdown and channel avulsion, which are associated with decline of river flow in the downstream direction typical of dryland streams. Decrease in river flow can lead to sediment deposition, decrease in channel capacity, vegetative invasion of the channel, overbank flows, and ultimately result in channel breakdown and changes in marsh formation. A similar process on established marshes may also lead to channel avulsion and marsh abandonment, with the subsequent invasion of terrestrial vegetation. All the previous geomorphological evolution processes have an effect on the established ecosystem, which will produce feedbacks on the hydrodynamics of the system and affect the geomorphology in return. In order to simulate the complex dynamics of the marshes we have developed an ecogeomorphological modelling framework that combines hydrodynamic, vegetation and channel evolution modules and in this presentation we provide an update on the status of the model. The hydrodynamic simulation provides spatially distributed values of inundation extent, duration, depth and recurrence to drive a vegetation model based on species preference to hydraulic conditions. It also provides velocities and shear stresses to assess geomorphological changes. Regular updates of stream network, floodplain surface elevations and vegetation coverage provide feedbacks to the hydrodynamic model.Ítem Acceso Abierto Detecting inundation thresholds for dryland wetland vulnerability(Elsevier, 2019-04-19) Sandi, Steven G.; Saco, Patricia M.; Saintilan, Neil; Wen, Li; Riccardi, Gerardo A.; Willgoose, Garry; Rodriguez, Jose F.Ítem Acceso Abierto Estuarine wetland evolution including sea-level rise and infrastructure effects.(EGU General Assembly 2015 © Author(s) 2015. CC Attribution 3.0 License., 2015-04) Rodriguez, Jose F.; Trivisonno, Franco N.; Sandi, Steven G.; Riccardi, Gerardo A.; Stenta, Hernan R.; Saco, Patricia M.Estuarine wetlands are an extremely valuable resource in terms of biotic diversity, flood attenuation, storm surge protection, groundwater recharge, filtering of surface flows and carbon sequestration. On a large scale the survival of these systems depends on the slope of the land and a balance between the rates of accretion and sea-level rise, but local man-made flow disturbances can have comparable effects. Climate change predictions for most of Australia include an accelerated sea level rise, which may challenge the survival of estuarine wetlands. Furthermore, coastal infrastructure poses an additional constraint on the adaptive capacity of these ecosystems. Numerical models are increasingly being used to assess wetland dynamics and to help manage some of these situations. We present results of a wetland evolution model that is based on computed values of hydroperiod and tidal range that drive vegetation preference. Our first application simulates the long term evolution of an Australian wetland heavily constricted by infrastructure that is undergoing the effects of predicted accelerated sea level rise. The wetland presents a vegetation zonation sequence mudflats - mangrove - saltmarsh from the seaward margin and up the topographic gradient but is also affected by compartmentalization due to internal road embankments and culverts that effectively attenuates tidal input to the upstream compartments. For this reason, the evolution model includes a 2D hydrodynamic module which is able to handle man-made flow controls and spatially varying roughness. It continually simulates tidal inputs into the wetland and computes annual values of hydroperiod and tidal range to update vegetation distribution based on preference to hydrodynamic conditions of the different vegetation types. It also computes soil accretion rates and updates roughness coefficient values according to evolving vegetation types. In order to explore in more detail the magnitude of flow attenuation due to roughness and its effects on the computation of tidal range and hydroperiod, we performed numerical experiments simulating floodplain flow on the side of a tidal creek using different roughness values. Even though the values of roughness that produce appreciable changes in hydroperiod and tidal range are relatively high, they are within the range expected for some of the wetland vegetation. Both applications of the model show that flow attenuation can play a major role in wetland hydrodynamics and that its effects must be considered when predicting wetland evolution under climate change scenarios, particularly in situations where existing infrastructure affects the flow.Ítem Acceso Abierto Hydrodynamics, vegetation transition and geomorphology coevolution in a semi-arid floodplain wetland.(EGU General Assembly 2016 © Author(s) 2016. CC Attribution 3.0 License., 2016-04) Sandi, Steven G.; Rodriguez, Jose F.; Saco, Patricia M.; Riccardi, Gerardo A.; Wen, Li; Saintilan, NeilÍtem Acceso Abierto Incorporating Infrastructure and Vegetation Effects on Sea Level Rise Predictions in Low-Gradient Coastal Landscapes(2015-12) Rodriguez, Jose F.; Sandi, Steven G.; Trivisonno, Franco N.; Saco, Patricia M.; Riccardi, Gerardo A.At the regional and global scales, coastal management and planning for future sea level rise scenarios is typically supported by modelling tools that predict the expected inundation extent. These tools rely on a number of simplifying assumptions that, in some cases, may result in important overestimation or underestimation of the inundation extent. One of such cases is coastal wetlands, where vegetation strongly affects both the magnitude and the timing of inundation. Many coastal wetlands display other forms of flow restrictions due to, for example, infrastructure or drainage works, which also alters the inundation patterns. In this contribution we explore the effects of flow restrictions on inundation patterns under sea level rise conditions in coastal wetlands. We use a dynamic wetland evolution model that not only incorporates the effects of flow restrictions due to culverts, bridges and weirs as well as vegetation, but also considers that vegetation changes as a consequence of increasing inundation. We apply our model to a coastal wetland in Australia and compare predictions of our model to predictions using conventional approaches. We found that some restrictions accentuate detrimental effects of sea level rise while others moderate them. We also found that some management strategies based on flow redistribution that provide short term solution may result more damaging in the long term if sea level rise is considered.Ítem Acceso Abierto Macquarie River floodplain flow modeling: implicaitons for ecogeomorphology(CRC Press, 2014) Sandi, Steven G.; Rodriguez, Jose F.; Saco, Patricia M.; Riccardi, Gerardo A.; Wen, Li; Saintilan, Neil; Stenta, Hernan R.; Trivisonno, Franco N.This work presents preliminary results of implementing of a quasi-2D hydrodynamic module (VHHMM 1.0) to simulate flows and flooding patterns throughout the Macquarie Marshes, south east Australia, in order to assess habitat requirements. The model uses an interconnected cell scheme that solves mass conservation and uses simplified versions of the momentum equations to represent flow between cells. This model has been used before to assess geomorphological changes in large river floodplains and vegetation evolution in estuarine wetlands, showing results consistent with cases of gradual floodplain inundation following overbank flow. The simplified characteristics of the quasi-2D model allow for an adequate representation of hydrodynamic processes with similar performance of other higher dimensional models. Model results and computational times are compared with outputs from a conventional 1D/2D model (MIKE FLOOD) applied to the same domain showing that the VHHMM 1.0 is adequate for representation of floods in the Macquarie Marshes.Ítem Acceso Abierto Patch organization and resilience of dryland wetlands(Elsevier, 2020-04) Sandi, Steven G.; Saco, Patricia M.; Rodriguez, Jose F.; Saintilan, Neil; Wen, Li; Kuzcera, George; Riccardi, Gerardo A.; Willgoose, GarryÍtem Acceso Abierto Predicting Sea-level Rise and Infrastructure Effects on Coastal Wetlands(Editorial to conference proceedings of 13th Hydraulics in Water Engineering Conference. HIWE2017, 2017-11-13) Rodriguez, Jose F.; Saco, Patricia M.; Sandi, Steven G.; Saintilan, Neil; Riccardi, Gerardo A.: Climate change predictions for Australia include an accelerated sea-level rise, wich challenges the survival of estuarine wetlands. Furthermore, coastal infrastructure poses and additional constraint on the adaptive capacity of these ecosystems. This paper presents results of wetland evolution based on hydro period and inundation depth experienced by vegetation, and computed using a hydrodynamic model. The application simulates the long-term evolution of wetland on the Hunter Estuary heavily constricted by infrastructure that is undergoing the effects of predicted accelerated sea-level rise. The wetland presents a vegetation zonation sequence mudflats –mangrove –saltmarsh from the seaward margin, but it also affected by compartmentalization due tu internal road embankments and culverts that effectively attenuates tidal inputs. Results of the modelo show that flow attenuation can play a major role in wetland hydrodynamics and that its effects can increase wetland vulnerability under climate change scenarios, particularly in situations where existing infrastructure affects the flow.Ítem Acceso Abierto Resilience to drought of dryland wetlands threatened by climate change(Nature Research, 2020) Sandi, Steven G.; Rodriguez, Jose F.; Saintilan, Neil; Wen, Li; Kuzcera, George; Riccardi, Gerardo A.; Saco, Patricia M.