Agricultural colonization of dynamic riverine islands …...Agricultural colonization of dynamic...
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Agricultural colonization of dynamic riverine islands in a tropical wandering river Livia Serrao 1 , Luz Elita Balcázar Terrones 2,3 , Hugo Alfredo Huamaní Yupanqui 2 , Juan Pablo Rengifo Trigozo 4 , Luca Brentari 5 and Guido Zolezzi 1 1 University of Trento, Department of Civil, Engineering and Mechanical Engineering – DICAM, Italy, 2 Universidad Nacional Agraria de la Selva –UNAS, Departamento de Ciencias Agrarias, Peru, 3 Instituto de Investigación de la Amazonía Peruana –IIAP, Perú, 4 Universidad Nacional Agraria de la Selva – UNAS, Departamento de Conservación de Suelos y Agua, Peru, 5 Fondazione Edmund Mach di San Michele all’Adige, Italy. email: [email protected] Introduction and case study Research question Methods Preliminary results: island bio-morphodynamics Conclusions References We investigate the interplay between riverine islands dynamics in a large tropical wandering river and their use by local communities for agricultural production. The study focuses on a piedmont reach of the wandering Huallaga river (76°2’56,69”W, 9°8’38.87”S), which drains the Peruvian Amazon. Riverine islands are characterized by a high space-time variability in active wandering river systems like the Huallaga, which results from biophysical interactions among flow, sediment transport and riparian vegetation. Despite the rapid rates of planform changes, islands in the Huallaga are extensively used by local farmers who mainly rely on rainfed, low tech agriculture. This piece of research is part of the international cooperation project entitled “Alto Huallaga - Sustainable Development and Fight against Climate Change” whose main aim is to enhance resilience of local farmers against climate and environmental changes. (i) Is there a correlation among morpho- dynamics experienced by the riverine islands and chemical and physical characteristics of their soil? (ii) Is morpho-dynamics a positive driver for agricultural vocationality? (iii) Have farmers developed agricultural practices adapted to morpho-dynamics and flood regimes? The identification of the riverine islands has been obtained through Landsat imagery analysis. The number of islands, their size and composition have been evaluated at reach and at sub-reach scale, showing high morphological dynamics and sub-reaches differences. The series of intensity-hue-saturation (IHS) elaborations showing the fluvial dynamics in the third sub-reach, indicates that Soto island formation occurs during 2011-2014. Thus, further Landsat scene have been elaborated at year-time scale in order to detect the several and rapid changes. Land cover changes within the evolving islands surface indicate the high dynamics that characterize this island sub-reach. White areas within the perimeter did not belong to the active bed area in each period. Aknowledgments Riverine Island Anthropic impact Morpho- dynamics Island evolution Shrinkage of wet bed Agriculture depending on flood regime Agricultural use REMOTE SENSING ANALYSES COMPUTING FIELDWORK LABORATORY (1) Coverage classification (water, vegetation, gravel) at reach scale by a semi-automatic procedure in GRASS-GIS environment of 8 Landsat scenes from 1986 to 2018. (2) Analysis of coverage classes changes in GRASS-GIS environment. (1) Elaboration of outputs from the semi-automatic procedure and computation of coverage percentage. (2) Assessment of 2 series of weights: (i) time evolution, with exponential expression, (ii) type of morpho-dynamics change, with eigenvalues of a comparative matrix. (1) Excavation of soil samples homogeneously displaced across the area of the riverine islands. (2) Identification of vertical soil profile with the classification and sampling of each layer. (3) Survey among local farmers. (1) Analyses of the main chemical and physical characteristics of soil samples to assess the agricultural vocationality: Organic Matter, Cation-exchange capacity, pH, N and P available, and texture. Gurnell, A.M., et al. 2002 Island-dominated landscape of large floodplain rivers, a European perspective, Freshwater Biology 47, 581-600. Moretto, J., et al. 2014 Channel Adjustments and island dymanics in the Brenta river (Italy) over the last 30 years, River Res. Applic. 30: 719-732. Spada, D., et al. 2018 Multi-Temporal Image Analysis for Fluvial Morphological Characterization with Application to Albanian Rivers, ISPRS Int J. Geo- Inf, 7(8). Zanoni, L., et al. 2008, Island dynamics in a braided river from analysis of historical maps and air photographs, River. Res. Applic. 24: 1141-1159 A more detailed analysis of three riverine islands in three different sub-reaches has been conducted to observe their generation process and evolution. This poster, focuses on Soto island, in the third sub-reach. Gracias a Breener, Daniel, Daniela, David, Alex, Dihana, Erwin, Fiorela, Mary, Thalia, Treicy, Viktor, Yonel. And thanks to Provincia Autonoma di Trento for supporting the Alto Huallaga cooperation project. Pajaro Bobo Tessaria Integrifolia First excavation Excavation and infiltration test All the three interviewed farmers reported that they use to crop according to the seasonal fluvial dynamics. They do not relate the soil fertility with flood regime, nevertheless two of them reported that they moved to the island due to the fertility of soils. The five sample locations and the three fields of the interviewed farmers are shown in the Figure on the right side. Vertical profiles of some chemical and physical characteristics of the five stratigraphies excavated are presented in the Figures below. Finally, the relation among soil characteristics and fluvial dynamics are presented in the Figures on the last row. M5 M2 M1 M4 M3 The study reach is highly dynamic with rapid turnover of vegetated islands. The relation among soil characteristics and fluvial dynamics is not evident yet. Further results on other two riverine islands in the same Shiringal reach will be key to confirm the preliminary results. However, the preliminary results show, in certain cases, such as pH and available P, a likely correlation. Preliminary results: island soil characteristics erosion vegetation colonization erosion, retreating banks deposit and colonization vegetation removal deposit
Transcript of Agricultural colonization of dynamic riverine islands …...Agricultural colonization of dynamic...
Agricultural colonization of dynamic riverine islands in a tropical wandering riverLivia Serrao1, Luz Elita Balcázar Terrones2,3, Hugo Alfredo Huamaní Yupanqui2, Juan Pablo Rengifo Trigozo4, Luca Brentari5 and Guido Zolezzi1
1 University of Trento, Department of Civil, Engineering and Mechanical Engineering – DICAM, Italy, 2 Universidad Nacional Agraria de la Selva –UNAS, Departamento de Ciencias Agrarias, Peru, 3 Instituto de Investigación de la Amazonía Peruana –IIAP, Perú, 4 Universidad Nacional Agraria de la Selva – UNAS, Departamento de Conservación de Suelos y Agua, Peru, 5 Fondazione Edmund Mach di San Michele all’Adige, Italy.
email: [email protected]
Introduction and case study
Research question
Methods
Preliminary results: island bio-morphodynamics
Conclusions
References
We investigate the interplay between riverineislands dynamics in a large tropical wandering riverand their use by local communities for agriculturalproduction. The study focuses on a piedmontreach of the wandering Huallaga river(76°2’56,69”W, 9°8’38.87”S), which drains thePeruvian Amazon. Riverine islands arecharacterized by a high space-time variability inactive wandering river systems like the Huallaga,which results from biophysical interactions amongflow, sediment transport and riparian vegetation.Despite the rapid rates of planform changes,islands in the Huallaga are extensively used bylocal farmers who mainly rely on rainfed, low techagriculture. This piece of research is part of theinternational cooperation project entitled “AltoHuallaga - Sustainable Development and Fightagainst Climate Change” whose main aim is toenhance resilience of local farmers against climateand environmental changes.
(i) Is there a correlation among morpho-dynamics experienced by the riverine islandsand chemical and physical characteristics oftheir soil?
(ii) Is morpho-dynamics a positive driver foragricultural vocationality?
(iii) Have farmers developed agriculturalpractices adapted to morpho-dynamics andflood regimes?
The identification of the riverine islands hasbeen obtained through Landsat imagery analysis.The number of islands, their size and
composition have been evaluated at reach andat sub-reach scale, showing high morphologicaldynamics and sub-reaches differences.
The series of intensity-hue-saturation (IHS)elaborations showing the fluvial dynamics in thethird sub-reach, indicates that Soto islandformation occurs during 2011-2014. Thus,further Landsat scene have been elaborated atyear-time scale in order to detect the severaland rapid changes.Land cover changes within the evolving islandssurface indicate the high dynamics thatcharacterize this island sub-reach. White areaswithin the perimeter did not belong to theactive bed area in each period.
Aknowledgments
Riverine Island
Anthropic impact
Morpho-dynamics
Island evolution
Shrinkage ofwet bed
Agriculturedepending
on flood regime
Agriculturaluse
REMOTE SENSING ANALYSES
COMPUTING
FIELDWORK
LABORATORY
(1) Coverage classification (water, vegetation, gravel) at reach scaleby a semi-automatic procedure in GRASS-GIS environment of 8Landsat scenes from 1986 to 2018. (2) Analysis of coverage classeschanges in GRASS-GIS environment.
(1) Elaboration of outputs from the semi-automatic procedure andcomputation of coverage percentage. (2) Assessment of 2 series ofweights: (i) time evolution, with exponential expression, (ii) type ofmorpho-dynamics change, with eigenvalues of a comparativematrix.
(1) Excavation of soil samples homogeneously displaced across thearea of the riverine islands. (2) Identification of vertical soil profilewith the classification and sampling of each layer. (3) Survey amonglocal farmers.
(1) Analyses of the main chemical and physical characteristics ofsoil samples to assess the agricultural vocationality: OrganicMatter, Cation-exchange capacity, pH, N and P available, andtexture.
Gurnell, A.M., et al. 2002 Island-dominatedlandscape of large floodplain rivers, a Europeanperspective, Freshwater Biology 47, 581-600.Moretto, J., et al. 2014 Channel Adjustments andisland dymanics in the Brenta river (Italy) over thelast 30 years, River Res. Applic. 30: 719-732.Spada, D., et al. 2018 Multi-Temporal Image
Analysis for Fluvial Morphological Characterizationwith Application to Albanian Rivers, ISPRS Int J. Geo-Inf, 7(8).Zanoni, L., et al. 2008, Island dynamics in a braidedriver from analysis of historical maps and airphotographs, River. Res. Applic. 24: 1141-1159
A more detailed analysis of three riverine islandsin three different sub-reaches has beenconducted to observe their generation process
and evolution. This poster, focuses on Sotoisland, in the third sub-reach.
Gracias a Breener, Daniel, Daniela, David, Alex, Dihana, Erwin, Fiorela, Mary, Thalia, Treicy, Viktor, Yonel.And thanks to Provincia Autonoma di Trento for supporting the Alto Huallaga cooperation project.
Pajaro BoboTessaria Integrifolia
First excavation Excavation and infiltration test
All the three interviewed farmers reported thatthey use to crop according to the seasonalfluvial dynamics. They do not relate the soilfertility with flood regime, nevertheless two ofthem reported that they moved to the islanddue to the fertility of soils. The five samplelocations and the three fields of the interviewedfarmers are shown in the Figure on the rightside. Vertical profiles of some chemical andphysical characteristics of the five stratigraphiesexcavated are presented in the Figures below.Finally, the relation among soil characteristicsand fluvial dynamics are presented in theFigures on the last row.
M5M2
M1
M4
M3
The study reach is highly dynamic with rapidturnover of vegetated islands. The relationamong soil characteristics and fluvial dynamics isnot evident yet. Further results on other tworiverine islands in the same Shiringal reach will
be key to confirm the preliminary results.However, the preliminary results show, in certaincases, such as pH and available P, a likelycorrelation.
Preliminary results: island soil characteristics
erosionvegetation colonization
erosion, retreating banks
deposit and colonizationvegetation removal
deposit
