Piave River Research Articles

Modeling arboreal vegetation-induced friction and its influence on river flooding using a two-dimensional model

Extensive research on vegetation flow resistance at the laboratory scale has yielded numerous formulations for determining vegetation friction coefficients. However, implementing and validating these equations at the river scale is often complex due to the lack of data on vegetation features and flow characteristics during floods, resulting in a limited number of field application studies. In this research, we use the Telemac-2D hydrodynamic model in a new case study to evaluate the performance of five vegetation friction formulations applied to arboreal vegetation. Employing vegetation data acquired through field surveys and LiDAR, along with flow data collected during one of the highest peak floods recorded on the Piave River, we built a two-dimensional (2D) river model. This model considers existing arboreal vegetation and terrain conditions to compare observed water surface elevations (WSE) during the flood with those simulated using vegetation friction equations. Our findings reveal that all tested equations perform similarly in all simulations. While these equations overestimated WSE throughout most of the flood, they accurately predicted levels at the highest peak and its proximity. Additionally, we explore several vegetation scenarios, varying density and percentage of area covered by arboreal vegetation, to assess their effect on water levels and flood risk.

The Empire Strikes Back: A Chemical Warfare Burn 100 Years After the First World War Ending.

During the First World War, the territories that constituted the front line in North East Italy were the theaters of intense shelling. The military tactics of the time involved the use not only of conventional ammunition but also of special ammunition containing asphyxiating and blistering compounds. However, the technology of the time did not guarantee a high explosion rate, leaving a considerable quantity of unexploded material on the ground. Although more than 100 years have passed since the end of the Great War, it is still common to find unexploded ordnance in the areas that were the site of combat. The demining campaign is still underway by the bomb squad of the Italian army with the medical support of the Military Corps of the Italian Red Cross. This case report reports the case of a young patient who came into contact with a vesicant chemical bomb along the Piave River and was subsequently admitted to the Major Burns Center of the Padua Hospital, where he was treated until full recovery. Although it is a rather rare eventuality, experiences like this provide the opportunity for the admitting surgeon to promptly and competently manage patients exposed to chemical warfare.

Quantifying groundwater recharge in the Venetian high plain between the Brenta and Piave Rivers through integrated surface–subsurface hydrological modeling

Study regionVenetian high plain between the Brenta and Piave Rivers, Northeast Italy. Study focusGroundwater recharge is the process by which aquifers, i.e., the groundwater reservoirs, are replenished. In many regions, recharge fluxes are currently declining due to more frequent hydroclimatic extreme events and unsustainable land use management. In this study, CATHY (CATchment Hydrology), an integrated surface–subsurface hydrological model (ISSHM), is used to estimate current and future recharge fluxes in a study area that represents an important source of drinking water supply for the Treviso province (Veneto Region, Northeast Italy). In particular, we aim to evaluate the impacts on recharge of a scenario with changed irrigation management, planned in compliance with European directive indications, to decrease water withdrawals from the Piave River and preserve its ecological flow. The model was first calibrated through a combination of FePEST and the Shuffled Complex Evolution algorithm, whereby both the bottom of the unconfined aquifer and the hydraulic conductivity field were tuned. After a validation step, the resulting model was used to simulate a scenario in which the flood irrigation method, currently the most widespread in the study area, is fully replaced by sprinkler irrigation. New hydrological insights for the regionOur results show that, in response to a 50 % decrease in water withdrawn from the Piave River, the total recharge decreases by about 10 %, with a local reduction in groundwater head, mainly limited in wells located in the area directly affected by the conversion of the irrigation technique. The model suggests that most of the recharge fluxes occur in irrigated areas where the hydraulic conductivity is higher. Overall, this work resulted in the development of an ISSHM capable to reproduce groundwater dynamics and its drivers at high resolution and large scale. Although it can still be improved, the model represents a useful tool to investigate possible responses of the considered hydrosystem to future land use and climate change.

Monitoring Discharge in Vegetated Floodplains: A Case Study of the Piave River

The accurate assessment of discharge in vegetated floodplains during floods is a persistent challenge in river engineering due to the difficulty of acquiring hydraulic data, the variability in vegetation roughness, and the limitations of on-site vegetation characterization. This study introduces a novel approach that combines the continuous slope-area method with LiDAR-derived vegetation data and water depths measured with piezoresistive sensors to evaluate floodplain discharges while considering variations in roughness coefficients induced by arboreal vegetation. We apply this approach to a specific reach of the Piave River in Italy using data collected during the December 2020 flood event. The study demonstrates the capability of the employed measurement system to record extreme floods and emphasizes the importance of including vegetation roughness variations in floodplain discharge calculations. The proposed approach has the potential to be applied in similar scenarios, providing valuable insights for floodplain discharge estimation in vegetated areas.

The role of in-channel vegetation in driving and controlling the geomorphic changes along a gravel-bed river

Gravel-bed rivers are fluvial systems featuring highly complex morphological and evolutionary patterns because of their configuration characterized by the contemporary presence of many distinct morphological units. Complexity can also be observed in the response of gravel-bed rivers to flow conditions, which can be highly varied. This work aims to analyze the evolution of gravel and vegetated areas in a gravel-bed river during a period of persistent low flow conditions, focusing also on the responses exhibited by the different types of riparian vegetation. To this end, a 2200 m-long segment of the Piave River (NE Italy) was considered. It was surveyed twice by LiDAR (August 2003 and August 2010), permitting the analysis of the spatial-temporal evolution of gravel and vegetated areas through both cover type analysis and the DoD technique. During the study period (August 2003 – August 2010), the flow conditions were constantly ordinary, i.e., under-bankfull. The cover type analysis stressed an increase of +115 % in vegetated areas, which have diffusely colonized the river corridor. However, the low flow conditions also induced geomorphic changes with 54 % of the study area affected by variations in surface elevation. The DoD computed a diffuse deposition over the main and secondary channels, while erosion was observed in specific areas of the main fluvial island and along the right floodplain. In terms of vegetation changes, five eroded patches were identified, which contributed to 60 % of the vegetated area entirely eroded in the study reach. These patches were mainly characterized by mature vegetation taller than the mean vegetation height observed over the study reach. Therefore, the analysis of the response of the Piave River to persistent under-bankfull flows stressed a complex evolution of the gravel and vegetated areas, which can be appreciated also because of low flow conditions, emphasizing the composite dynamics typical of a gravel-bed river. These results could improve riverine management considering vegetation structure and dimension, as well as the geomorphic settings of gravel-bed rivers in view of future low flow conditions.

Modeling dissolved and particulate organic carbon dynamics at basin and sub-basin scales

Dissolved organic carbon (DOC) and particulate organic carbon (POC) play a fundamental role in biogeochemical cycles of freshwater ecosystems. However, the lack of readily available distributed models for carbon export has limited the effective management of organic carbon fluxes from soils, through river networks and to receiving marine waters. We develop a spatially semi-distributed mass balance modeling approach to estimate organic carbon flux at a sub-basin and basin scales, using commonly available data, to allow stakeholders to explore the impacts of alternative river basin management scenarios and climate change on riverine DOC and POC dynamics. Data requirements, related to hydrological, land-use, soil and precipitation characteristics are easily retrievable from international and national databases, making it appropriate for data-scarce basins. The model is built as an open-source plugin for QGIS and can be easily integrated with other basin scale decision support models on nutrient and sediment export.We tested the model in Piave river basin, in northeast Italy. Results show that the model reproduces spatial and temporal changes in DOC and POC fluxes in relation to changes in precipitation, basin morphology and land use across different sub-basins. For example, the highest DOC export were associated with both urban and forest land use classes and during months of elevated precipitation. We used the model to evaluate alternative land use scenarios and the impact of climate on basin level carbon export to Mediterranean.

Assessing 40 Years of Flood Risk Evolution at the Micro-Scale Using an Innovative Modeling Approach: The Effects of Urbanization and Land Planning

The present work is aimed at assessing the change in time of flood risk as a consequence of landscape modifications. The town of San Donà di Piave (Italy) is taken as a representative case study because, as most parts of the North Italy floodplains, it was strongly urbanized and anthropized in the last several decades. As a proxy for flood risk, we use flood damage to residential buildings. The analysis is carried out at the local scale, accounting for changes to single buildings; GIS data such as high-resolution topography, technical maps, and aerial images taken over time are used to track how the landscape evolves over time, both in terms of urbanized areas and of hydraulically relevant structures (e.g., embankments). Flood hazard is determined using a physics-based, finite element hydrodynamic code that models in a coupled way the flood routing within the Piave River, the formation of levee failures, and the flooding of adjacent areas. The expected flood damage to residential buildings is estimated using an innovative method, recently proposed in the literature, which allows estimating how the damage evolves during a single flood event. The decade-scale change in the expected flood damage reveals the detrimental effect of urbanization, with flood risk growing at the pace of a fraction of urbanized areas. The within-event time evolution of the flood damage, i.e., how it progresses in the course of past or recent flood events, reflects changes in the hydrodynamic process of flooding. The general methodology used in the present work can be viewed as a promising technique to analyze the effects on the flood risk of past landscape evolution and, more importantly, a valuable tool toward an improved, well-informed, and sustainable land planning.

Sustainability of an Open-Loop GWHP System in an Italian Alpine Valley

Shallow geothermal systems (SGSs) for building climatization represent an advantageous alternative to traditional air-conditioning systems, resulting in economic and environmental benefits. Installation of these systems requires knowledge of site-specific geological and hydrogeological conditions, which in feasibility studies are often evaluated only at the single plant scale, lacking a comprehensive view and risking not to guarantee the system sustainability over time. In this paper a methodology for the sustainable design of SGSs is presented. The methodology is developed from an example on the aquifer scale in Longarone (Belluno, Italy), where three groundwater heat pumps (GWHPs) were installed in an industrial area located in a mountain basin hosting a coarse-grained phreatic aquifer, characterized by sediments with high hydraulic conductivity and proximal to a large river (Piave River). Open-loop systems were first analyzed through numerical modeling using FEFLOW software, identifying peculiar features of the aquifer, due to its interaction with surface waters, and suggesting the possibility of its greater geothermal exploitation. Subsequently, a relationship between flow rates and thermal plume extensions was obtained, which is useful to providing support in the evaluation of potential interference with neighboring systems. The study at the aquifer scale proved representative of the system, highlighting the criticalities of the area, such as trends of aquifer temperature alteration, interference between plants, and thermal feedback.

Satellite flood detection integrating hydrogeomorphic and spectral indices

ABSTRACT Satellite remote sensing is a highly valuable data source useful in the monitoring of surface water dynamics and an essential tool in flood risk management although several factors can interfere with the detection of water features. This study explores an approach that integrates satellite optical images and DEM-based hydrogeomorphic features to enhance real‐time identification of river flooding. Spectral indices, namely MNDWI and the combination of NDWI/NDTI, were taken from Sentinel-2 images and used to detect flooded areas, while DEMs were used to identify areas more exposed to river flooding using the Geomorphic Flood Index. The integration/overlapping of these layers allowed us to refine the final map with a significant detection improvement compared to those based exclusively on the segmentation of a spectral index. The proposed integrated approach was tested in five areas of the Piave river (Northern Italy) where a flooding event caused by the Vaia storm took place in October 2018. Results have been evaluated against reference maps produced manually in five selected areas, demonstrating good capabilities of the proposed procedure (mean accuracy 0.90), significantly reducing false alarms (Matthews Correlation Coefficient improvements among 0.02–0.43 in 4 out of 5 areas). The key advantages of such a procedure are the rapid application and the free and easy availability of the data that, in turn, allow for the investigation of large areas in the aftermath of an event.

Are Stones Living?

The article addresses a new theme in anthropology, focusing on intra-actions among humans and the mineral world. Within an anthropology of the environment, in the context of the Italian Piave river, where water and stones were described by old gatherers as living beings, my ethnography discerns a European form of animism that attributed subjectivity, intentionality, ability and agency to non-humans, revealing an interspecies network of relationships hidden by the western naturalistic worldview. These data contribute to a reflection on Descolian ontological animism, recomposing the discrepancies of perspectives vised as contrasting, as the Ingoldian perception of the living being, De Castro’s perspectivism, and Barad’s new materialism, towards an anthropology of life.

Textural Characteristics of the Holocene Sandy Ridges in the Eastern Venetian Coastal Plain (North Adriatic Sea, Italy)

In the lower Piave river coastal plain (northeast of the Venice Lagoon, Italy), evidences of ancient sandy ridges testify to both the local coastline progradation and retrogradation that occurred during the Holocene. Their arrangement is recognizable in aerial photographs as they appear as groups of parallel sandy strips. The orientation of each group of ridges differs from the orientation of the others. Even if the ridges have not preserved their original relief and morphology, weak undulations are still locally present. Through the joint interpretation of textural parameters and geomorphological observations and measurements, an attempt has been made to define the depositional processes responsible for the formation of these sandy ridges. The results from grain-size analyses have given evidence of the foreshore and the backshore environments. They have confirmed the presence of both aeolian deposits in most of the sampled sandy ridges and fine-grained filling sediments containing organic matter in the old inter-ridge depressions. The investigations have also confirmed the existence of a well-preserved abandoned Piave river delta and four subsequent main stages of coastal progradation interrupted by episodes of coastal retreat. Therefore, this research has provided new insights into the evolution of the Holocene Venetian coastal plain by adding new information on the different coastal depositional environments and transporting agents.

Imago proelii. La cartografia storica della Prima Guerra Mondiale dal Museo Storico della Terza Armata: spigolature per una analisi tipologica e semiologica

International historiography has extensively assessed the innovations in war practice experienced during the First World War. However, the consequences of trench warfare in military cartographic production have not been fully investigated yet. Following this line, the essay presents the cartographic corpus of the historical archive of the Terza Armata (Third Army); the Terza Armata had a fundamental role in the conflict, settling on the Piave river after Caporetto and leading the final advance towards Istria. The analysis of the collection, which is still unpublished, can open a new front of research aimed at developing categories of semiological analysis and typological classification of military maps as sources produced in fieri, i.e. manuscript IGM maps that were constantly updated during war operations. First, the cartographic corpus is presented; second, a first typological classification and a semiological decoding of maps are proposed, based on the interpretation of the symbols used, of the legend and of the methods of representation. In particular, the contribution focuses on tactical maps, i.e. cartographies that were continuously updated in proelio to document the evolution of war events on the front line.

Shaped by Power

As a piece of larger research which focuses on the relation between the exercise of power over water resources, the contribution examines the current environmental exhaustion of the north-Italian mountain landscape resources exploring the interplay of ecological transformation of the alpine area with the multiplicity of processes of rationalization of the territory. The essay questions the territorial implications of the politics of exploitation of water, focusing on the capitalocene landscapes of the Piave river. Bisecting the region through a valley-section, it describes how its embedded dynamics of production are closely entangled, and consequently dependent upon, the ecologies of specific spaces, often seemingly disconnected or remote. In the current frame of increasingly worsen climate conditions, this contribution attempts to question the socio-political and ecological dynamics that the machinic landscape entails across the territory, would it be urbanised or rural.

An Alpine Energy Transition: The Piave River from Charcoal to “White Coal”

Abstract This article analyzes the environmental history of the Industrial Revolution by examining the evolution of the usage and management of the waters of the Piave, a river stretching from the eastern Alps to the Venetian Plain. In the preindustrial period, the Piave played a fundamental role in defining the flows of raw materials and energy in the region, representing the main route for transporting timber—the most important resource of the time—from Alpine forests to lowland urban areas. The onset of industrialization, especially the development of a railway network, undermined both this role and the economic activities that had been based on the exploitation of Alpine forests. The subsequent rise of hydroelectricity transformed the Piave from a transport route to an energy source. This transformation caused, in a shift applicable to more than just the Italian case, a redefinition of the social and economic relationships between upland and lowland areas: after the energy transition, the Alpine region ceased to be a constituent part of an interdependent system and instead became a periphery to an urban core.

Assessment of the geomorphic effectiveness of controlled floods in a braided river using a reduced-complexity numerical model

Abstract. Most Alpine rivers have undergone significant alterations in flow and sediment regimes. These alterations have notable effects on river morphology and ecology. One option to mitigate such effects is flow regime management, specifically through the reintroduction of channel-forming discharges. The aim of this work is to assess the morphological changes induced in the Piave River (Italy) by two distinct controlled-flood strategies, the first characterized by a single artificial flood per year and the second by higher-magnitude but less frequent floods. This work involved applying a two-dimensional reduced-complexity morphodynamic model (CAESAR-LISFLOOD) to a 7 km long reach, characterized by a braided pattern and highly regulated discharges. Numerical modelling allowed the assessment of morphological changes for four long-term scenarios (2009–2034). The scenarios were defined considering the current flow regime and the natural regime, which was estimated by a stochastic physically based hydrologic model. Changes in channel morphology were assessed by measuring active-channel width and braiding intensity. A comparison of controlled-flood scenarios to a baseline scenario (i.e. no controlled floods) showed that artificial floods had little effect on channel morphology. More channel widening (13.5 %) resulted from the high-magnitude flood strategy than from the application of the other strategy (8.6 %). Negligible change was observed in terms of braiding intensity. The results indicate that controlled floods do not represent an effective solution for morphological recovery in braided rivers with strongly impacted flow and sediment regimes.

Vittorio Veneto: zadnja italijanska ofenziva na reki Piavi leta 1918

Category: 1.01 Original scientific paper Language: Original in Slovene (Abstract in Slovene and English, Summary in English) Key words: Vittorio Veneto, southwestern front, First World War, Austria-Hungary, Italy, Italian offensive Abstract: Based on the study of archival sources and literature, the author analyses the conditions in the Austro-Hungarian Monarchy and on the southwestern front in 1918. This is followed by an analysis of the preparations for and the course of the Italian offensive at Vittorio Veneto which lasted from October 24 to November 4, 1918. The goal of the Italian Armed Forces was to achieve a decisive breakthrough on the front sector Valdobbiadene–Feltre, in the lower part of the Piave river. After initially successes in resisting, the Austro-Hungarian Armed Forces began to fall apart and was forced to withdraw. The Italian victory ended the war on the southwestern front and caused the collapse of the Austro-Hungarian Armed Forces and the signing of an armistice between Italy and Austria-Hungary. The Austro-Hungarian army, then, began to withdraw while the Italian army carefully and slowly followed and occupied all areas promised to them under the London Memorandum.

Glacial dynamics in pre-Alpine narrow valleys during the Last Glacial Maximum inferred by lowland fluvial records (northeast Italy)

Abstract. During the Last Glacial Maximum (LGM), most of the major glaciated basins of the European Southern Alps had piedmont lobes with large outwash plains; only a few glaciers remained within the valley. Piedmont glaciers have left well-preserved terminal moraines, which allow for investigations to be carried out and inferences to be made regarding their evolution and chronology. Valley glaciers' remnants, on the contrary, are often scantly preserved, and changes can only be detected through correlations with glaciofluvial deposits in downstream alluvial basins. The Brenta glacial system's dynamics in the glacier's terminal tract have been inferred through a wide range of sediment analysis techniques on an alluvial stratigraphic record of the Brenta megafan (northeast Italy), and via the mapping of in-valley glacial/glaciofluvial remnants. Glaciers flowing across narrow gorges could possibly be slowed/blocked by such morphology, and glacial/sediment fluxes may then be diverted to lateral valleys. Moreover, narrow valleys may induce glaciers to bulge and form icefalls at their front, preventing the formation of terminal moraines. The Brenta Glacier was probably slowed/blocked by the narrow Valsugana Gorge downstream of Primolano and was effectively diverted eastwards across a wind gap (Canal La Menor Valley), joining the Cismon/Piave glaciers near Rocca and ending ∼2 km downstream. The Cismon and Piave catchments started to contribute to the Brenta system just after 27 ka cal BP until at least ∼19.5 ka cal BP. After the glaciers collapsed, the Piave River once again flowed into its main valley, whilst the Cismon continued to merge with the Brenta. This investigation shows that glacial catchments may vary significantly over time during a single glaciation in rugged Alpine terrains. Sand petrography and the chemical/mineralogical composition of sediments are powerful proxies for tracing such variations, as they propagate through the glacial and glaciofluvial systems and can be recognized in the alluvial stratigraphic record far downstream from the glacier front.

Antifouling properties of different Plasma Electrolytic Oxidation coatings on 7075 aluminium alloy

In this work the antifouling properties of different Plasma Electrolytic Oxidation (PEO) coatings produced on samples of 7075 aluminum alloy were studied and compared with those of samples treated with more commercial treatments, such as traditional anodizing and painting, and untreated ones. After the treatments, the different samples were characterized through scanning electron microscope (SEM) observations. The antifouling tests were carried out immersing the different coated samples in the Piave river for a month, collecting one sample series every week. After the immersion test, to evaluate the colonization by microalgae, the samples were investigated through stereomicroscope, inverted light microscope, and SEM. Results showed that the addition of silver/copper particles in the electrolyte does not modify the PEO process, obtaining thick and adherent coatings that contain particles both inside and outside of the pores. As regards the antifouling properties, surface PEO treated with copper particles exhibited a good effect inhibiting the colonization by microalgae.

Test of methodology for developing a large wood budget: A 1-year example from a regulated gravel bed river following ordinary floods

Wood budgeting is a current approach for quantifying the spatial and temporal variations of in-channel large wood (LW). Despite its importance for a proper LW management, the assessment of LW budget is still a challenge because of the complexity of LW dynamics. Focusing on a 3.7 km-long gravel-bed reach of the Piave River (North-eastern Italy), this study proposes an attempt to assess a short-term (1 year) LW budget as a consequence of ordinary floods (RI < 1 yr). Lateral recruitment, mobilization and deposition of LW were investigated by two field surveys conducted at the beginning and end of the study period. The lateral input was evaluated by measuring, positioning and tagging all standing trees (diameter ≥ 0.1 m) within a 20 m-wide buffer strip along the floodplain and island perimeters. Bank erosion was checked by measuring the riverbanks with a differential Global Positioning System (dGPS), during the first and second survey. Contemporarily, the position and characteristics of each fluvial wood element (diameter ≥ 0.1 m and length ≥ 1 m) within the active channel was determined. These short-term analyses revealed that ordinary floods are not able to induce relevant variations in the LW abundance and redistribution of in-channel wood. Nevertheless, the results highlighted the role of riverbank erosion in supplying LW to the active channel. Episodic inputs of LW from bank erosion were also observed during ordinary flood events, introducing 33% (0.21 m3·km−1) of the total LW input amount. Results on LW transport showed that, in the Piave River, both deposition and mobilization of LW may also occur during low flow conditions (i.e. 14% of bankfull stage) without causing important variations in the wood quantity. However, the low magnitude of floods was reflected in the small amount of LW involved in the input (0.4 m3·km−1) and output (0.7 m3·km−1) processes, pointing out that sites for deposition and mobilization of LW are conditioned by flood magnitude and morphological settings. The combination of recruitment, mobilization and deposition processes resulted in a slight decrease of LW storage (−0.07%), while including also the anthropic removal of LW the amount of wood storage decreased to −9.7%. Despite the short-term investigation, this work sheds further light on LW processes, providing useful results for the management of LW in wide piedmont rivers.

Mobility and fate of Thallium and other potentially harmful elements in drainage waters from a decommissioned Zn-Pb mine (North-Eastern Italian Alps)

The potential impact of decommissioned mining areas on the quality of water resources is an issue of major concern for local communities. Acid mine drainage resulting from hydrolysis and oxidation of metal sulphides associated with mineral veins or mining wastes is often responsible for leaching large amounts of potentially harmful elements (PHEs) in solution, which can be dispersed into the surrounding environment and affect the quality of the recipient water bodies.The aim of the present study was to investigate the geochemical properties of the mine drainage waters at the decommissioned Salafossa mine (North-Eastern Italian Alps), to highlight anomalous concentrations of PHEs outflowing from the currently flooded galleries and to elucidate their speciation.In spite of the Zn-Pb sulphides still present in the body ore, there is no evidence of acid drainage waters from the mine galleries as a result of the buffering effect produced by carbonate host rocks. Due to their high mobility, however, Zn and Tl are present in solution mostly in ionic form. Conversely, the less mobile Pb, is preferably partitioned in the solid phase. Additionally, the oxidising conditions of the drainage waters also allow the precipitation of some PHEs (As, Cd, Pb, Tl, Zn) in the form of Fe-Mn oxy-hydroxides and carbonates, which accumulate at the bottom of the mine galleries as fine “sediments” or concretions. Drainage waters inside the mine were found to be highly enriched in Zn (up to 16mgL‐1), Fe (up to 5mgL‐1) and Tl (up to 260μgL‐1). Their concentrations, however, are partially diluted in the mine due to a mixing with less mineralised waters before being discharged into the Piave River, the major tributary downstream from the mining area. Although drainage waters are still characterised by high concentrations of Tl (about 30μgL‐1) at their outflow, dilution in the Piave River seems to be the only natural process mitigating the impact of PHEs within the drainage basin.