We propose a methodology to calibrate a stochastic model for riparian vegetation dynamics that is based on real data. The methodology integrates various tools that are often used individually in fluvial investigations and it is here applied to the case of the Cinca river (Spain), aiming to explore how its riparian vegetation responds to changing climate conditions

Carlo Camporeale

Matteo Bertagni

Melissa Latella

Paolo Vezza

English

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)

18 October 2022POLITECNICO DI TORINORepository ISTITUZIONALEAn integrated methodology for the riparian vegetation modelling / Latella, Melissa; Bertagni, MATTEO BERNARD;Vezza, Paolo; Camporeale, CARLO VINCENZO. - ELETTRONICO. - (2021), pp. 201-202. ((Intervento presentato alconvegno 6th IAHR Europe Congress tenutosi a Warsaw, Poland nel June 30th – July 2nd, 2020.OriginalAn integrated methodology for the riparian vegetation modellingPublisher:PublishedDOI:Terms of use:openAccessPublisher copyright(Article begins on next page)This article is made available under terms and conditions as specified in the  corresponding bibliographic description inthe repositoryAvailability:This version is available at: 11583/2873422 since: 2021-07-14T10:56:10ZIAHR2 IAHR 2020 – ABSTRACT BOOKEditor-in-ChiefPhD Eng. Monika KalinowskaEditorial BoardProf. Paweł RowińskiProf. Tomasz OkruszkoPhD Michael NonesISBN 978-83-66847-01-9IAHR 2020 – ABSTRACT BOOK 2016th IAHR Europe Congress, June 30th – July 2nd, 2020, Warsaw, Poland  An integrated methodology for the riparian vegetation modelling Melissa LATELLA1, Matteo BERTAGNI1, Paolo VEZZA1, Carlo CAMPOREALE1 1 Department of Environmental, Land and Infrastructure Engineering, Polytechnic of Turin, 10129, Turin, Italy email: melissa.latella@polito.it ABSTRACT We propose a methodology to calibrate a stochastic model for riparian vegetation dynamics that is based on real data. The methodology integrates various tools that are often used individually in fluvial investigations and it is here applied to the case of the Cinca river (Spain), aiming to explore how its riparian vegetation responds to changing climate conditions. 1. Introduction The riparian biome is a transitional habitat that connects aquatic and terrestrial ecosystems, supporting very high biodiversity and offering a wide range of ecosystem services. However, this fundamental and fragile environment is currently threatened by anthropogenic and climate factors. Therefore, models that are able to provide a deeper understanding of the complex and interdependent processes underlying the riparian dynamics and predict future scenarios are urgently needed. 2. Methodology This work aims to combine most of the fluvial approaches adopted in the literature (statistical analysis of field data, analytical and numerical modelling) into an integrated methodology to calibrate a stochastic model and provide riparian vegetation statistics for current and future scenarios.  The theoretical basis of the methodology is the minimalist eco-hydrological stochastic model CR06 (Camporeale and Ridolfi 2006). CR06 describes the dichotomic switching between biomass decay and growth in relation to the topography and the randomness of water stage fluctuations. As output, CR06 gives the analytic steady-state probability density function (pdf) of the vegetation biomass and its moments. In this model, the vegetation behaviour is parametrized by the dimensionless carrying capacity, i.e. the maximum biomass reached in optimal soil conditions, and a flood-induced decay rate. CR06 provides closed solutions for the computation of these biological parameters for very simplified geometries. However, its implementation over real fluvial environments requires a proper calibration, which we defined through a three-step methodology:  1. Collection of hydrological, biological and sediment data for the study site; 2. Definition of the water level statistics through two-dimensional hydrodynamic modelling; 3. Calibration of the biological input parameters of CR06 on the basis of the collected data. Eventually, the calibrated CR06 can be used as a local impact model to investigate how the vegetation distribution varies when the hydrological conditions change. 3. Application to a real case We applied the methodology to two adjacent bars of the Cinca river in Spain, within a segment approximately 9 km long. For this site, a record of the average daily flow rate since 1947 and LiDAR data acquired in 2016 were available. LiDAR data were processed with FUSION/LDV to obtain the site topography and the vegetation heights. In addition, a field survey was carried out on November 26th-28th, 2018 to assess the hydraulic roughness. For this purpose, 520 samples were collected through the Wolman Pebble Count and the grain size distribution was defined with BaseGrain. Data about vegetation height and diameter were also collected to regress site-specific allometric relationships for the biomass estimation.  Starting from the collected sediment and hydrological data, and the LiDAR-derived topography, we carried out two-dimensional hydrodynamic modelling. 19 simulations for different flow rates were launched with Delft3D obtaining the water depth distribution over the two fluvial bars. The probability of inundation was then computed and used as input for the following calibration of the biological parameters of CR06. In the present study we discuss the restoration effort of Karla wetland analyzing the pressures which may affect the restoration process linking them with the wetland’s ES. Our purpose is to correlate in a conceptual manner the basic pressures with the measures implemented to counteract them, the ecosystem actual status and the affected ES. This can be seen as an important lesson for the management of a sensitive ecosystem, including a baseline for further steps. For this reason, the main pressures, the undertaken restoration measures and the current status were summarized by monitoring data and modeling results that have been gathered by officially published researches (eg. Sidiropoulos et al., 2017; Latinopoulos et al., 2020) and regional authorities. As for the ES, these were and described in basic groups proposed by CICES (2015).  3. Results and conclusions Τhe matrix containing the main pressures and the relevant restoration measures that have been undertaken so far, along with the actual present ecosystem status and their effect on ES is presented (Table 1). Table 1. Main pressures with the relevant measures undertaken Pressure Restoration measure Status (based on field monitoring and modelling) Ecosystem Services (Category/Classification according CICES, 2015) Flooding Implementation of flood protection and mountainous water projects and of collectors/ Diversion of flooded water into the reservoir with the pumping stations operation Full operation of pumping stations and reservoirs, absence of mountainous water projects Flood protection (regulating) Agricultural crops (provisioning) Land barren (regulating) Sediment regulation Point and diffuse pollution sources Treatment of inflow water to the reservoir, improvement of water quality/Establishment of riparian zones, operation of a peripheral buffer zone, construction and operation of artificial wetland Slight improvement of water quality, Bad Ecological Status, Dominance of cyanobacteria Water quality Good ecological status (regulating) Recreation (cultural) Biodiversity (regulating) Habitat fragmentation Tree planting project, creation of land corridors, buffer zones Good conservation status on terrestrial habitats, loss of littoral habitat’s connectivity and ecosystem naturalness Raw materials for energy (regulating) Maintaining/Conserving population and habitats (regulating) Water availability (irrigation, drinking water) Creation of the main reservoir and distributing irrigation channels, drinking water system indirect use, after the recharge of groundwater aquifer Complete construction of irrigation system. Incomplete construction of the drinking water system Agricultural crops (provisioning) Drinking water (provisioning) In conclusion, the new created wetland could lie at the very core of Europe’s Green Infrastructure (European Commission, 2013). It could act as an important wetland in terms of sustainability but also could deliver many socio-economic services. Our study shows that we have to review and understand the ecosystem’s processes before and after dryness in order to achieve a successful restoration and a sustainable ecosystem functioning. References  Alexakis D, Kagalou I, Tsakiris G (2013) Assessment of pressures and impacts on surface water bodies of the Mediterranean. Case study Pamvotis Lake, Greece, Environmental Earth Sciences. 70, 687–698 Bullock JM, Aronson J, Newton AC, Pywell RF, Rey-Benayas JM (2011) Restoration of ecosystem services and biodiversity: conflicts and opportunities. Trends in Ecology & Evolution, 26, 541-549 Dufour S, Piegay H (2009) From the myth of a lost paradise to targeted river restoration: forget natural references and focus on human benefits. River Research and Applications, 25, 568–581. Elliott M, Burdon D, Hemingway KL, Apitz S (2007) Estuarine, coastal and marine ecosystem restoration: confusing management and science - a revision of concepts. Estuarine. Coastal and Shelf Science, 74, 349-366 European Commission (2013) Building a Green Infrastructure for Europe, European Union, Belgium doi.org/10.2779/54125 Goldyn R, Podsiadlowski S, Dondajewska R, Kozak A (2014) The sustainable restoration of lakes-towards the challenges of the Water Framework Directive. Ecohydrology and. Hydrobiology, 14, 68–74 Kurth A.M., Schirmer, M., 2014. Thirty years of river restoration in Switzerland: implemented measures and lessons learned. Environ. Earth Sci. 72 (6), 2065–2079 Latinopoulos D, Ntislidou C, Kagalou I (2016) Multipurpose plans for the sustainability of Greek Lakes: emphasis on multiple stressors. Environmental Processes, 3, 589–602 Latinopoulos D, Dimitriou A, Kagalou I (2020) Modelling water related Ecosystem Services in a heavily modified Mediterranean reservoir using the Soil and Water Assessment Tool (SWAT) (submitted)  NRC - National Research Council (1992) Restoration of Aquatic Ecosystems: Science, Technology, and Public Policy. National Academy Press, Washington, DC. Sidiropoulos P, Chamoglou M, Kagalou I (2017) Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece), Ecohydrology & Hydrobiology, 17, 177–189  202 IAHR 2020 – ABSTRACT BOOKDuring the calibration phase, the whole study site was divided into cells, successively ranked in classes according to their probability of inundation. For each class, the average hydrological and topographic parameters were computed and pairs of values for the carrying capacity and decay rate were found through a least square process that optimizes the fit between theoretical and real pdfs. The calibrated decay factor satisfactorily reflects the species zonation along the riparian transects, whereas the resulting carrying capacity values appear consistent with previous field observations, where the deepening of the phreatic surface was considered the major controlling factor for the maximum plant size.  Despite the simplicity of the adopted model, the calibration gives enough information to correctly recreate the biogeography of the riparian zone. Indeed, it provides an excellent match between the map of the spatial distribution of the calibrated and the real pdf first moment (Fig. 1a-b). Numerically speaking, the overall percentage absolute difference between the two maps of the computed and real mean biomass amounts to 9.3% and 3.3%, for the first and second bar, respectively.  Finally, the calibrated model was used as a local impact model to investigate the consequences of mean annual daily flow rate reduction, which is expected to be 40% by 2100 in the study site (Alfieri et al., 2015). To this aim, new hydrological statistics were computed through hydrodynamic modelling and the calibrated CR06 was applied again to provide a forecast of the vegetation evolution in the new scenario. According to the results, the expected hydrological change induces a dramatic drop in the riparian biomass (Fig. 1c), meaning that the negative effect of phreatic lowering largely exceeds the beneficial reduction of flooding. Not even the adoption of adaptation strategies by the vegetation can completely mitigate this negative impact (Fig. 1d). Therefore, these results highlight the controlling role of the phreatic surface on vegetation within the study site.   Fig. 1. Real (a) and computed (b) distribution of the mean vegetation biomass within the two modelled bars for the present scenario. Distribution for the future scenario with (c) and without (d) the adoption of adaptation strategies by the vegetation.  4. Conclusions A methodology to calibrate the minimalist model CR06 was proposed and applied to the real case of the Cinca river. The methodology innovatively integrates different river science tools, ranging from theoretical morphodynamics and stochastic processes to geomatics and field activities. Furthermore, it effectively provides a functional description of the riparian vegetation biomass in the current hydrological conditions and forecasts potential future scenarios. References  Alfieri L, Burek P, Feyen L, Forzieri G (2015) Global warming increases the frequency of river floods in Europe, Hydrology and Earth System Sciences, 19, 2247-2260 Camporeale C, Ridolfi L (2006) Riparian vegetation distribution induced by river flow variability: A stochastic approach, Water Resources Research, 42, W10415   

An integrated methodology for the riparian vegetation modelling

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An integrated methodology for the riparian vegetation modelling

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