Drainage Network Research Articles

Hydrosedimentary behavior of a field combining surface drains and tile drains

In agricultural fields, soil erosion is usually associated to surface runoff. However, in drained fields, tile drains are additional pathways for soil particles. Few studies have quantified erosion in drained fields and they mainly focused on tile drained fields, without considering fields combining surface and tile drainage. These studies show high inter-site and inter-annual variabilities that highlight the need for more annual quantifications of erosion in drained fields. Consequently, it is still difficult to quantify the relative importance of the factors affecting soil erosion in drained fields. In addition to a comprehensive review of the existing studies of erosion through drainage, this study aims at quantifying surface and subsurface erosion in a 5 ha cultivated field combining surface and tile drainage. Suspended sediments (SS) and water fluxes have been monitored during two years (2019–2020 and 2020–2021) at a high temporal resolution (1 min), both at the outlet of the tile drain network and at the outlet of the surface drainage rill. SS yield was 0.49 t ha−1 and 1.08 t ha−1 in 2019–2020 and 2020–2021, respectively. During 2019–2020 and 2020–2021, tile drainage contribution to the total runoff was 46% and 21%, respectively and its contribution to SS yield was 9% and 11%, respectively. High temporal resolution measurements of runoff and SS concentrations showed the suspended sediment concentration in the surface drain runoff only increase by 17% from the first to the second study year. Conversely, for tile drainage, average suspended sediment concentrations increased by 260%. These variations and the increase of surface runoff rate suggest a shift in water and sediment connectivity at the field scale. Cropping practices could have generated a slumping of the soil surface during the second year and, at the same time, the development of a macropore network in the subsoil. Cropping practices induced changes of surface horizon characteristics and their impact on the hydrosedimentary behavior of drained soils need to be further studied. This study confirms previous results concerning the temporal dynamics of SS exports in a drained context under temperate climate and adds a new quantification of hydrosedimentary fluxes in a surface and tile drained field separating surface drains and tile drains contributions.

Stream laws in analog tectonic-landscape models

Abstract. The interplay between tectonics and surface processes defines the evolution of mountain belts. However, correlating these processes through the evolution of natural orogens represents a scientific challenge. Analog models can be used for analyzing and interpreting the effect of such interaction. To fulfill this purpose it is necessary to understand how the imposed boundary conditions affect analog models' evolution in time and space. We use nine analog models characterized by different combinations of imposed regional slope and rainfall rates to investigate how surface processes respond to the presence of tectonically built topography (imposed slope) under different climatic conditions (rainfall rate). We show how the combination of these parameters controls the development of drainage networks and erosional processes. We quantify the morphological differences between experimental landscapes in terms of a proposed Se/R ratio, accounting for both observables and boundary conditions. We find few differences between analog models and natural prototypes in terms of parametrization of the detachment-limited stream power law. We observe a threshold in the development of channelization, modulated by a tradeoff between applied boundary conditions.

Evaluating real-time control of stormwater drainage network and green stormwater infrastructure for enhancing flooding resilience under future rainfall projections

Traditional stormwater control measures are designed to handle system loadings induced by fixed-size storm events. However, climate change is predicted to alter the frequency and intensity of flooding events, stimulating the need to explore another more adaptive flooding solution like real-time control (RTC). This study assesses the performance of RTC to mitigate impacts of climate change on urban flooding resilience. A simulated, yet realistic, urban drainage system in Salt Lake City, Utah, USA, shows that RTC improves the flooding resilience by up to 17% under climatic rainfall changes. Compared with green stormwater infrastructure (GSI), RTC exhibits a lower resistibility, lower flooding failure level, and higher recovery rate in system performance curves. Results articulate that keeping RTC's performance consistent under ‘back-to-back’ storms requires a tradeoff between upstream dynamical operation and downstream flooding functionality loss. This research suggests that RTC provides a path towards smart and resilient stormwater management strategy.

Water Management of Agricultural Lands in Diyala Governorate

The existence of a large water deficit in Diyala Governorate, especially in July and August of the year 2020-2021 AD, and the reasons are due to the natural factors to which Iraq in general and the study area in particular were exposed, such as thermal inclusion and lack of precipitation, and human factors that are specific to the water policies of neighboring countries and events After 2003, a number of factors and field manifestations also combined to complicate the picture of the water deficit in the study area, represented in the pollution and lack of purification of waterways and the disruption of many water barriers and lifting stations. It was found from the results of analyzes of river water samples The drains have a quality within the second category (C 2). As for the drainage water, it was shown that it has a salinity of (2215-2230) micromoz / cm, and it falls within the third category (C3) and it is of high salinity. This water is used only in the presence of an effective drainage network and for crops High tolerance to salinity.

Assessing the benefits of real-time control to enhance rainwater harvesting at a building in Cape Town, South Africa

In the period 2015–2017, the City of Cape Town, South Africa, faced the possibility of taps running dry due to a prolonged drought. To mitigate the impacts of water scarcity, many households installed rainwater tanks to harvest water to use for non-potable purposes such as toilet flushing and washing. The installation of the rainwater tanks was mainly arbitrary, in response to perceived impact of water scarcity rather than a systematic needs assessment. This study was thus undertaken to determine the available opportunity to optimise the use of these rainwater tanks using real-time control (RTC) techniques. Many studies have demonstrated the potential of rainwater harvesting (RWH) systems to supplement potable water supply and minimize stormwater flows to downstream drainage networks. RTC technology can be used to enhance the performance of RWH systems in achieving these two objectives, by receiving a rainfall forecast and initiating pre-storm release in real time. In this study, RTC was applied on the RWH system at the New Engineering Building, University of Cape Town (UCT) to enhance water supply and increase rainwater retention period. The performance with RTC was compared with the conventional management of the RWH system. It was determined that RWH with RTC technology was generally superior in simultaneously achieving water supply and rainwater retention benefits compared to the conventional management approach. RTC provides an active operation which optimizes the performance of the system across varying conditions but requires an assiduous management process designed to meet set objectives. It was concluded that the active release mechanism employing RTC exhibited great potential; the system opens up the possibility of delivering a more robust and reliable system due to its ability to provide failure detection and centralised control. The system can readily be adapted to variation of local climatic conditions in the short and long term.

Study of Characteristics and Management of Drainage Problems in Ubud District

Ubud District is one of the tourism areas in Bali which is growing very rapidly. Ubud District has problems related to inundation and flooding which often occur during the rainy season. The drainage canals cannot accommodate the peak flood discharge. Because the capacity of the channel is insufficient, besides the influence of sediment and garbage, water overflows through the freeboard of the channel. This study aims to determine the characteristics of inundation and drainage in Ubud District. Primary and secondary data are used in this study which will then be used in data analysis. The analytical method used are field survey, identification of inundation and flood locations, inventory of existing drainage system, hydrology and hydraulics analysis, and drainage network planning. The result is 27 inundation locations were found in Ubud District. The inundation locations included 5 points in Lodtunduh Village, 3 points in Mas Village, 2 points in Peliatan Village, 5 points in Petulu Village, 2 points in Sayan Village, and 10 points in Ubud Village. The duration of the inundation that occurs is a minimum of 15 minutes and a maximum of 360 minutes. The height of the inundation that occurs is 12 – 50 cm with an inundation area of 0.032 – 4.67 ha and an inundation length of 12 – 2.309 m. The frequency of inundation is 3 to 10 times per year. Parameters for determining priority for drainage management based on priority scale are determined based on the characteristic parameters of inundation, economic losses, social disturbances and government facilities, transportation disturbances, and losses in residential areas. The recommendations given include normalizing the existing canal with river stone pairs of the required size that are more adequate to accommodate water discharge, especially during rains; making diversion channel with precast box culvert with the required size; and construction of new channels equipped with inlet drains per segment as entry points for inundation on the roads into the drainage channels.

Physical resilience of riverside cities against floods

Human societies today pay attention to natural disaster control more than ever, yet floods are still among destructive hazards. Researchers are constantly seeking solutions to mitigate the damages associated with floods and increase urban resilience against them. This study explored the assessment of urban physical resilience to floods, rapid recovery from flood shocks, and enhancement of urban functioning over time. This was an applied study using a descriptive-analytical method. The research population consisted of experts in urban affairs. First, the research variables and indices were extracted through the theoretical foundations, and then, validity testing was used to identify the most effective indicators. A review of the research literature showed a lack of consensus on a coherent model for flood damage assessment across different urban zones and the identification of effective indices. Therefore, HEC-GeoRAS (a program for inundation mapping) was used for flood Vulnerability zoning of the Cheshmeh Kileh River Region, Based on this, three zones Vulnerable to floods were determined. The proposed model and its algorithms are structured based on GIS statistical modeling, which accurately zones the urban fabric around the river based on Vulnerability severity and accurately identifies vulnerabilities. This model did not follow the current methods that limit river buffer zones to two categories inside and outside the river's buffer zone; rather investigated the zones based on the Vulnerability severity of urban cover classes (e.g., roads and buildings). The research findings suggest that the conditions of the existing buffer zone deviate from those recommended by the modeling results. Meanwhile, a historical analysis of floods shows that the affected areas match those identified by the software. In all studied zones, the primary cause of the Vulnerability is the absence of surface water drainage networks, non-standard constructions, and road network-related restrictions, which exacerbate the crisis conditions. The existence of large area (coarse-grained) plots can be considered a point of strength in all zones, which presents an opportunity to modify the urban fabric in the future.

Hydraulic characteristics of a sluice gate over a broad-crested weir

Vertical sluice gates are commonly used to control and measure flow in irrigation and drainage networks. To reduce their size and associated maintenance and operation costs, they are sometimes installed above broad-crested weirs. To explore the effects of the installation location of the sluice gate and the sill height on the hydrodynamic characteristics of the flow passing through the sluice-gated weir, six laboratory models were tested. The 427 and 449 data points included both free- and submerged-flow conditions, respectively. Analytical relationships were developed for the contraction, head-loss, and Henry's (1950) discharge coefficients. Based on the maximization of the discharge and contraction coefficients and the minimization of the head-loss coefficient, results suggest that a gate should be installed at a distance of L/2 (where L is the sill length) from the upstream end of the weir crest, and the height of 1.25Hd (where Hd is the water depth as referenced from the weir sill elevation) is the optimal height for the weir. By conducting experiments and constructing correlations for determining the contraction and head-loss coefficients under free flow conditions, the average values of these coefficients for the laboratory models were obtained as 0.664 and 0.133, respectively. Applying the average contraction and head-loss coefficients to the developed relationship for estimating the free and submerged discharge coefficients resulted in an error of 4% and 6%, respectively. WinGate alpha 0.2 software was used to estimate the experimental free and submerged discharge coefficient of the gated weir with an average error of 5.4% and 12.7%, respectively. It was done without any consideration of the cross-section shape of the weir or the location of the gate on the weir sill. In addition, an inspection of the submergence threshold of the gated weir showed an increase in the submergence threshold when the gate was moved further downstream from the upstream end of the sill.

The role of thermokarst evolution in debris flow initiation (Hüttekar Rock Glacier, Austrian Alps)

Abstract. A rapid sequence of cascading events involving thermokarst lake outburst, local rock glacier front failure, debris flow development, and river blockage hit Radurschl Valley (Ötztal Alps, Tyrol) on 13 August 2019. Compounding effects from permafrost degradation and drainage network development within the rock glacier initiated the complex process chain. The debris flow dammed the main river of the valley, impounding a water volume of 120 000 m3 that was partly drained by excavation to prevent a potentially catastrophic outburst flood. We present a systematic analysis of destabilizing factors to deduce the failure mechanism. The identification and evaluation of individual factors reveals a critical combination of topographical and sedimentological disposition, climate, and weather patterns driving the evolution of a thermokarst drainage network. Progressively changing groundwater flow and storage patterns within the frozen sediment accumulation governed the slope stability of the rock glacier front. Our results demonstrate the hazard potential of active rock glaciers due to their large amount of mobilizable sediment, dynamically changing internal structure, thermokarst lake development, and substantial water flow along a rapidly evolving channel network.

Investigating the Impact of Flood on Low Lying Settlements of Delhi, India: A Planning Perspective

In the past, the Yamuna River and the Najafgarh Drainage System have flooded the city of Delhi severely. In the past 33 years, Yamuna has 25 times exceeded its risk threshold, which is set at 204.83m. Since 1900, Delhi has suffered six significant floods when the Yamuna River has reached a height of one metre or more above the accidental 204.49m on the old railway bridge (2.66m above the accident level). These floods happened in 1924, 1947, 1976, 1978, 1988, and 1995. The Yamuna recently climbed more than two metres beyond the danger threshold in Delhi, breaking the milestone 207 metres for the first time in 32 years. The second highest point, at 206.92 metres, was on September 27, 1988. There is a direct impact of floods on the Yamuna River and the city drainage network. People who live along the Yamuna River Belt, on the river's banks, and in the drain are impacted by this. The amount of the solid regions causing local floods has increased landslides as a result of deforestation and local floods. Low-lying communities, particularly haphazard colonies that fall into the water, will be most impacted by this. Hathinikund erupts high in Haryana because of the persistent, intense rainfall on the high cliffs, draining water upstream, continuing to flood Delhi and harming the lives of those who live in low-lying areas. Therefore, torrential rains caused severe damage to the city, and even more so to those families built on the wrong side, which were the first and most frequent sightings of their homes and property being flooded. Families had already begun to lose livestock and livestock during this time, before being evacuated and their situation remains so dire that one has to leave the rest of the house to relocate and relocate when the water level drops. The purpose of the study was to explore about the kind of impacts generally inhabitants face during and post flooding and to find out the implementation of strategies. The following methods were used: Site survey of the case study area in which structured questionnaire and observations were conducted through primary survey, analysis and assessment, study of issues and concerns. As a result, flood prevention, preparedness and mitigation strategies with reference to low lying area have been analyzed and planning recommendations have been proposed.

Mio‐Pliocene exhumation of the hinterland and sediments provenance of the Neogene strata from Kumaun Himalaya of northwest India: Insights from detrital fission‐track thermochronology

Fission‐track (FT) thermochronological analysis of detrital apatite and zircon derived from the lower and middle Siwalik Group of the sub‐Himalaya allows the reconstruction of the long‐term exhumation history of the Higher Himalayan Crystalline (HHC) and Lesser Himalayan Sequence (LHS), and also the provenance of the Siwalik sediments. Here, we report 14 detrital apatite and zircon fission‐track (AFT/ZFT) ages of lower and middle Siwalik subgroups of the Kumaun region, northwest Himalaya. Detrital FT ages suggest that all sandstone samples were never buried below the temperature range of 90° to 100°C and remained as unreset to retain a signal of source‐area exhumation. A detrital AFT age from sandstone sample at close proximity to the Main Boundary Thrust (MBT) is 4.4 ± 0.5 Ma (Pliocene time) which is completely reset and younger than the depositional age, while the detrital ZFT ages of the same sample are unrest. The AFT age represents the time of reactivation of the MBT during which ZFT ages were not affected. This study revealed that the provenances of Siwalik sediments are located majorly in the MBT hinterland areas and the nearest sources are Amritpur granite, the outer Lesser Himalayan meta‐sedimentary (LHMS) zone, Almora klippe, Ramgarh thrust sheet, and the overlying Tethyan Himalayan Sequence. These source areas can be attributed to the development of local drainage networks in the Ramganga‐Kosi drainage basin during late Miocene to Pliocene (i.e., ~9 to 4 Ma). Based on detrital FT datasets, it has been envisaged that different tectonic activities in the MBT hinterland area between Miocene and Pliocene Periods cause the tectonic upliftment and exhumation of source areas and supply the sediment to the Siwalik foreland basin.

GEOMORPHOLOGICAL INDICATORS OF SHEAR DISPLACEMENTS ON THE URUP ISLAND (GREAT KURIL RIDGE)

The Urup Island, located in the southern part of the Great Kuril ridge, is an interesting object of study because its relief is very contrasting and has a significant depth of vertical dissection. It was greatly influenced by the recent tectonic processes. Judging by the geological data, the island at the present stage is located in a shear stress field with the southeastern orientation of the axis of maximum compression. It can be explained by the subduction interaction of the Pacific and Sea of Okhotsk lithosphere plates at an acute angle of about 55°. Visual and automated decoding of satellite images and digital terrain models, and the analysis of the erosion network pattern made it possible to identify geomorphologic signs of shear displacements. These include the echeloned arrangement of lineaments as separation cracks in right-lateral shear zone in the area of the Rybnaya River and on the Skvoznyakovyj isthmus, where displacements of unidentified kinematics were previously revealed. The zones, which are oriented in the north-east direction and differ in the asymmetric pattern of the drainage network, were considered: within their limits, small tributaries are located on one side of the watercourse of the highest order as megatracks of separation. In the area of the epicenter of the earthquake of 1989, which occurred under the latitudinal horizontal stretching, a linear lowering of the relief with a feathery pattern of watercourses was recorded, interpreted as a morphostructure of stretching. Similar probably stretching zones, extending mainly along the azimuth of 130-140°, were recorded on the Pacific coast of the island. Their orientation, as well as the kinematics of probable shear displacements identified from the geomorphologic data, correlates with the general ideas about the stress-strain state of the Southern Kuriles, as well as the reconstruction of the main normal stress axes of the Kastricum Peninsula performed by us from the fracture measurements. All this prove that the suggested structural-geomorphologic interpretation of the Urup Island territory is quite reasonable. In general, our new data on the configuration and kinematics of probable active shear faults and extensional morphostructures complement the existing ideas about the latest deformations of the study area.

SuDS as a climate change adaptation strategy: Scenario-based analysis for an urban catchment in northern Italy

Urbanization and climate change effects on precipitation are the leading cause of flood risk increase in urban settlements. Sustainable Drainage Systems (SuDS) are effective strategies to improve city resilience toward flooding but usually they are designed to meet performance standards based on historical climate settings. The reported modeling scenario-analysis strives for investigating the potential of SuDS as adaptation strategy to a projected medium-term climate change affecting Sesto Ulteriano (Milan, Northern Italy). Two drainage models, a benchmark scenario reproducing the drainage network current configuration and a designed scenario involving SuDS retrofitting, were tested under historical (observed) and expected future precipitation extremes (projected) to assess and compare hydrological and hydraulic variables essential for the definition of a Precipitation Variability Adaptation Index (PVAI), which measures the adaptation strategy performance. Results indicate that even though SuDS were confirmed as effective flood control measures, their adaptability potential is affected by changes in rainfall severity indeed. In particular, the multi-variable PVAI, a global index able to take into account the effects of different determinants for an overall assessment of SuDS potential as adaptation strategies to climate changes, decreases when rainfall frequency decreases, among the same climate scenario, or when rainfall intensity increases due to climate changes.

Use of water generated by air conditioners for non-potable purposes

This study aims to evaluate the feasibility of using condensate water from air conditioners for non-potable purposes in a hospital building located in the city of Recife-PE, Brazil. The applied methodology was divided into the following steps: investigation of the amount of water generated by the condensate, where it was used in three ways to observe the volume of water produced, the first through the collection with a graduated cylinder and application of equations, the second through hydrometers installed in the condensate drainage network and the third by installing a rain gauge with arduino in the equipment drain. The second methodological step was to take the non-potable consumption demands of the building to the points that consume garden watering, cooling towers and hospital hygiene by washing and mopping the floors. The results show that the equipment in the building has the potential to generate a significant amount of water, with an estimated value greater than 640 m³ if it were to collect water from all equipment. In some periods, the condensate water from all the equipment would be able to meet 92.6% of the building demand. These results are positive in relation to the amount of water produced by air conditioning equipment, in order to meet the demands that do not require potable water for their activities, thus presenting a new water source for buildings.

ANTHROPOGENIC TRANSFORMATION OF THE LYUTITSA RIVER BASIN

The Liutytsia is a typical small river of the Polissya part of the Volyn region. It flows through the territory of Rozhyshche and Kopachivka united territorial communities. The river is 37 km long, with a catchment area of 208 km2, 3.6% forest cover, 1.4% marshland, and 60.5% ploughed. About 10,000 people live within the basin. The territory has long been developed. Agricultural use predominates. Specialisation: growing potatoes, cereals, industrial crops, dairy and meat farming and processing of agricultural products. In the structure of land use in the basin, 87.6% of the land is used for agricultural purposes. All land available for agricultural use has been ploughed and is actively used. Within the basin, the permissible land use limits are exceeded. This contributes to the aggravation of the environmental situation and requires the implementation of measures for the rational use of natural resources and nature protection. 8.8% of the basin's territory is occupied by settlements, industrial, transport, communications, etc. The basin's water resources are also actively used. Most of the water is used for water supply to the population, industry and agriculture. In a year of 95% runoff availability, total water withdrawals exceed 20% of the annual runoff, and irreversible water consumption in the basin is 15%. In the future, runoff shortages may become a problem in low-water years. The frequency of dry years has been increasing recently. The concentration of most chemicals in the river water does not exceed the maximum permissible concentration. The content of ammonium nitrogen exceeds the per capita values by 15.6 times in the first and 2.92 times in the river channel 2, nitrite nitrogen by 1.7 times and 1.91 times, respectively, and total iron by 16 times and 2.4 times. The excessive content of nitrogen compounds is caused by surface runoff from urban areas, fields, farms, and spontaneous solid waste dumps. The area of drained land within the basin is 8,606 thousand hectares, with a land reclamation rate of 41.4%. There are 5 drainage systems within the basin. Soil overdrainage is widespread within the basin's drainage systems, leading to loss of soil cohesion, loss of vegetation cover and deflation. With distance from the drainage network, water drainage is worse, there are waterlogged areas, rewetting occurs due to inefficient drainage channels that are silted and overgrown with vegetation. Some reclaimed areas have not been ploughed for many years and are overgrown with selfseeding. Hazardous exogenous processes are occurring within the basin: karst, secondary waterlogging, and siltation of the riverbed. Soils are also undergoing negative changes. Erosion processes are occurring, the depth of the humus horizon is decreasing, and the content of humus and plant nutrients is decreasing. Environmental problems in the basin include: violation of water protection zones, ploughing and rewetting of the floodplain; lack of hydroecological monitoring in the river basin; poor condition of drainage systems; lack of soilprotective technologies for growing crops, violation of recommendations for the use of drained land; illegal landfills in the basin; low forest cover, lack of protected areas within the basin, lack of an effective local ecological network.
 Keywords: river basin, geoecological state of the basin, sources of anthropogenic impact within the basin, anthropogenic transformation of the basin.

Impact of lockdowns and possible quantification of pollution sources on the water quality of the Yamuna River

ABSTRACT The COVID-19 lockdown halted industrial and transportation networks, resulting in a change in the level of pollution. In this study, the analysis of pre- and post-lockdown water quality of the Yamuna River is done, and primary causes are identified, by considering five in situ parameters and four Landsat-8-derived parameters. During the 2020 lockdown, pollution-indicating in situ parameters decreased, with chemical oxygen demand decreasing the most, possibly due to reduced industrial impact. All satellite-derived indices improved during lockdown and post-lockdown periods of 2020. Even in segments with uniform flow, floating algal index and normalized difference vegetation index exhibited lower levels. In contrast, the examination of the 2021 lockdown revealed no noteworthy insights. Mapping the observations with the drainage network and location of common effluent treatment plants revealed that industrial effluents were the dominant cause of water quality fluctuations. This demonstrates the impact of industrial effluents on the degrading water quality of Yamuna.

Assessing runoff control of low impact development in Hong Kong's dense community with reliable SWMM setup and calibration

Low impact development (LID) is a sustainable practice to managing urban runoff. However, its effectiveness in densely populated areas with intense rainfall, such as Hong Kong, remains unclear due to limited studies with similar climate conditions and urban patterns. The highly mixed land use and complicated drainage network present challenges for preparing a Storm Water Management Model (SWMM). This study proposed a reliable framework for setting up and calibrating SWMM by integrating multiple automated tools to address these issues. With a validated SWMM, we examined LID's effects on runoff control in a densely built catchment of Hong Kong. A designed full-scale LID implementation can reduce total and peak runoffs by around 35–45% for 2, 10 and 50-year return rainfalls. However, LID alone may not be adequate to handle the runoff in densely built areas of Hong Kong. As the rainfall return period increases, total runoff reduction increases, but peak runoff reduction remains close. Percentages of reduction in total and peak runoffs decline. The marginal control diminishes for total runoff while remaining constant for peak runoff when increasing the extent of LID implementation. In addition, the study identifies the crucial design parameters of LID facilities using global sensitivity analysis. Overall, our study contributes to accelerating the reliable application of SWMM and deepening the understanding of the effectiveness of LID in ensuring water security in densely built urban communities located near the humid-tropical climate zone, such as Hong Kong.

Gully development on the foredune of Pehuén Co (SW Buenos Aires Province, Argentina) and its relationship with rainfall and human activities

Understanding gully development is necessary to protect beach foredunes efficiently against gully erosion. The evolution of gullies on the foredune of Pehuén Co, Argentina, was explained using a combination of satellite images analysis and UAV models. In 16 years, the area covered by gullies increased 2011.4 m2 (5.6 times in size). The runoff due to precipitation is the major natural erosive agent affecting the active gully field, and its expansion is related to annual rainfall and the recurrence of rainy days. However, man-originated elements changed the drainage network and modified gully development, mainly by the construction of an unpaved road. The influence of the installation of Big Bags at the foredune toe, artificial nourishment, and the use of gullies as descents to the beach are also evaluated. Intervention is needed at gully incisions, mainly at the head of the catchments and early stages, particularly where the mass movement and the generation of cliffs have already begun. There is also a need to evaluate the location of road drainage to both reduce gully expansion and the creation of newer ones.

THE NECESSITY, SCIENTIFIC AND PRACTICAL PRINCIPLES OF IMPROVING METHODS OF DRAINAGE SYSTEMS DESIGN AND CALCULATION

The paper presents a new approach to improving the methods of design and calculation of drainage systems and their technical elements in the drainage mode and in the subsoil moistening mode. This was done on the basis of substantiating the connection of all technical elements of the system and taking into account the influence of their work efficiency on the effectiveness of regulating the water regime of drained lands. The existence and structure of the hierarchical and hydraulic relationship between the parameters of soil flow movement, the parameters of the closed collector-drainage network, and the parameters of canals and structures of drainage systems were determined based on the application of the system methodology. A physical model, a structural model, a mathematical model, and a hydraulic model of the drainage system were developed. By using these models, the principles of determining the parameters of the hydraulic characteristics of drainage or water supply (discharge, pressure, velocity etc.) for all elements (drained massif of reclaimed field, collector and drainage network, open canals of the network, main canal, water intake) in the entire range of variation with possible consideration of changes in slopes were obtained. The considered approach will make it possible to evaluate the efficiency of water flow movement simultaneously on every technical element and on the drainage system as their interconnection. In the future, this will make it possible to improve the methods of designing and calculating the technological and structural parameters of drainage systems, and thereby ensure the overall technical, technological, economic, and ecological efficiency of their functioning in accordance with modern conditions and requirements. This is a further improvement of the methods of design and calculation of drainage systems and their technical elements, taking into account the structural, hierarchical, and hydraulic relationship between them in accordance with modern conditions and requirements. This will make it possible to increase the validity and general technical, technological, ecological and economic efficiency of the creation and functioning of drainage systems during the implementation of adaptive measures regarding the changes in climatic conditions and the level of agricultural production in the area of drainage reclamation, for example, in Ukrainian Polissia. It will also provide an opportunity to ensure the necessary level of food security in the region and the country as a whole in the war and post-war periods.

Study on Drainage Network Pattern and Morphometric Analysis by Using Hydrology Support Algorithm

Abstract The degree of accuracy in the extraction of the drainage network and morphometric analysis of the basin plays a vital role in assessing geomorphological characteristics and hydrological processes. The extraction of the exact flow network from SRTM-DEM quantifies the drainage network, and morphometric parameters, which is the main objective of this study. The Thamirabarani river basin in Tamil Nadu, India is taken as the study area. The stream order threshold algorithm is used for stream rasterization to get the pattern of the basin’s drainage network. The hydrology-based algorithm uses a different range of threshold values to determine the stream pattern, which is comparable to the stream vectors of the toposheet. The drainage network distribution with a threshold value of 10000 gives many minor streams which imply dissimilarities with the stream network of toposheet, whereas the threshold value of 20000 shows remarkable similarity to an existing river system. The model with threshold 20000 provides a Stranhler-based drainage network with a basin area of 5664.52 km2. The basin is the fifth-order stream network with many lower-order streams. The drainage pattern is resulted in dendritic and sub-dendritic. The morphometric parameters of the basin are evaluated with the help of an aspect, slope, and contour. The slope of the study area is flat in the east and steeper in the west, along the area of Western Ghats. A bifurcation ratio ranges from 1.05 to 2.42, indicating that the drainage network is not influenced by structural disturbances in that area. The comprehensive evaluation of flow patterns along with morphometric properties obtained from this study provides data support for estimation of the volume of water in the basin, reservoir operation, and construction of hydrological structures. Also, this result can be used to compute watershed attributes normally used in hydrologic and water resources studies. The hydrology-based algorithm can be employed in other river basins to extract drainage network patterns.