River bed dynamic monitoring on ephemeral/intermittent rivers – sand-bed  response on topical drylands

2021 ◽  
Author(s):  
Jonas Souza ◽  
Fernando Alexandre ◽  
Gabriel Monteiro
Keyword(s):  
Water Level ◽  
Potential Evapotranspiration ◽  
Extreme Rainfall ◽  
Water Levels ◽  
Dynamic Monitoring ◽  
Tropical Rivers ◽  
Intermittent Rivers ◽  
Ephemeral Rivers ◽  
Rain Events ◽  
Morphology Changes

<p>Intermittent and ephemeral rivers, prevalent in dryland areas, have less monitoring data than perennial rivers worldwide. It hinders studies about hydro-geomorphology dynamics on these streams, which is especially complex in rain-fed flow regime on tropical rivers. Irregular rain patterns characterise the tropical drylands, which reverberate in the hydro-geomorphological dynamic. Unmanned Aerial Vehicles (UAV) survey is an efficient and cheap technic to monitor these streams since the dry periods expose the riverbed surface. This research aimed to analyse the hydro-geomorphology dynamic on sandy bed reaches of an intermittent tropical river. Five UAV surveys were realised on eight sandy reaches, from headwater to the outlet, between 2020 January 7 and December 9 in the Tigre River – Brazilian Drylands –, a 30Km ephemeral/intermittent. The UAV photos from all the surveys were co-aligned to create matching DEMs. We compared the DEMs to identify channel morphology changes, calculating differences in the riverbed and riverbank. The DEMs comparison enabled to calculate the erosion and sedimentation volume to each reach. Simultaneously, we installed crest stages gauges to monitor the peak water level between the surveys. Lastly, we used five rain gauges to identify the necessary rain volume that generates flow events. The 2020 annual rain volume was close to the historical average, between 530mm and 700mm, on the pediments, up to 1000mm on highland headwaters. The average potential evapotranspiration is around 1400-1800mm/year, due to the tropical climate. There was an average of 3.4 extreme rainfall daily events (over 50mm/day) during the year and the rainest period was between March 15 to 26<sup>th</sup> when rained from 134mm to 376mm around the watershed. The surveys between January 18 and March 8 identified insignificant morphology changes on eight reaches. The peak water levels were between no flow to 0.49m; only the outlet reach showed slight erosion and water level reaching 1.1m. The rain events between March 15/26<sup>th</sup> generate the water level annual peaks at all the reaches, from 1.9m to 5.4m (outlet reach). Seven reaches increased the vertical incision around 20/30cm to 80cm, and localised pools were eroded to up 1.7m deep. The outlet part exhibit around 30 to 40cm of sedimentation even with a water level peak of 5.4m. This unusual response could be caused by backwater effect from the Espinho River flood, which Tigre River is a tributary, that trapped sediment in the Tigre River. These results highlight how dynamic intermittent/ephemeral tropical rivers and showed how low-cost UAV High-Resolution DEMs and stage crests are workable and efficient techniques to monitor ungauged intermittent/ephemeral rivers. Simultaneously, narrow the surveys timespan (Covid-19 pandemic hindered most of the monthly planned surveys) is essential to identify which flow events caused erosion and sedimentation and which rain events trigger flow events.  </p><p>Keywords: Sand-bed rivers; UAV HR-DEMs; Brazilian Drylands; Water Level Stage Crest, riverbed erosion</p>

scholarly journals Vision-based system for the control and measurement of wastewater flow rate in sewer systems

2009 ◽  
Vol 60 (9) ◽  
pp. 2281-2289 ◽  
Author(s):  
L. S. Nguyen ◽  
B. Schaeli ◽  
D. Sage ◽  
S. Kayal ◽  
D. Jeanbourquin ◽  
...  
Keyword(s):  
Image Processing ◽  
Water Level ◽  
Water Levels ◽  
Combined Sewer Overflows ◽  
Web Based ◽  
Tier System ◽  
Crucial Information ◽  
Rain Events ◽  
Processing Techniques

Combined sewer overflows and stormwater discharges represent an important source of contamination to the environment. However, the harsh environment inside sewers and particular hydraulic conditions during rain events reduce the reliability of traditional flow measurement probes. In the following, we present and evaluate an in situ system for the monitoring of water flow in sewers based on video images. This paper focuses on the measurement of the water level based on image-processing techniques. The developed image-based water level algorithms identify the wall/water interface from sewer images and measure its position with respect to real world coordinates. A web-based user interface and a 3-tier system architecture enable the remote configuration of the cameras and the image-processing algorithms. Images acquired and processed by our system were found to reliably measure water levels and thereby to provide crucial information leading to better understand particular hydraulic behaviors. In terms of robustness and accuracy, the water level algorithm provided equal or better results compared to traditional water level probes in three different in situ configurations.

scholarly journals Return Level Analysis of the Hanumante River Using Structured Expert Judgment: A Reconstruction of Historical Water Levels

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3229
Author(s):  
Paulina E. Kindermann ◽  
Wietske S. Brouwer ◽  
Amber van Hamel ◽  
Mick van Haren ◽  
Rik P. Verboeket ◽  
...  
Keyword(s):  
Water Level ◽  
Historical Data ◽  
Classical Model ◽  
Expert Judgment ◽  
Water Levels ◽  
Return Level ◽  
Considerable Uncertainty ◽  
Level Data ◽  
Rain Events ◽  
Level Analysis

Like other cities in the Kathmandu Valley, Bhaktapur faces rapid urbanisation and population growth. Rivers are negatively impacted by uncontrolled settlements in flood-prone areas, lowering permeability, decreasing channels widths, and waste blockage. All these issues, along with more extreme rain events during the monsoon due to climate change, have led to increased flooding in Bhaktapur, especially by the Hanumante River. For a better understanding of flood risk, the first step is a return level analysis. For this, historical data are essential. Unfortunately, historical records of water levels are non-existent for the Hanumante River. We measured water levels and discharge on a regular basis starting from the 2019 monsoon (i.e., June). To reconstruct the missing historical data needed for a return level analysis, this research introduces the Classical Model for Structured Expert Judgment (SEJ). By employing SEJ, we were able to reconstruct historical water level data. Expert assessments were validated using the limited data available. Based on the reconstructed data, it was possible to estimate the return periods of extreme water levels of the Hanumante River by fitting a Generalized Extreme Value (GEV) distribution. Using this distribution, we estimated that a water level of about 3.5 m has a return period of ten years. This research showed that, despite considerable uncertainty in the results, the SEJ method has potential for return level analyses.

scholarly journals Estimativas dos Riscos de Chuvas Extremas nas Capitais do Nordeste do Brasil (Estimates of the Risks of Extreme Rainfall in Capitals of Northeast Brazil)

2016 ◽  
Vol 9 (2) ◽  
pp. 430 ◽  
Author(s):  
Francisco De Assis Salviano de Sousa ◽  
Valmir Rocha Vieira ◽  
Vicente de Paulo R. da Silva ◽  
Valneli Silva Melo ◽  
Roni Walter De Souza Guedes
Keyword(s):  
Water Saturation ◽  
Drainage System ◽  
Extreme Rainfall ◽  
Poor Quality ◽  
Water Levels ◽  
Unequal Distribution ◽  
Distribution Of Wealth ◽  
Rain Events ◽  
Unequal Distribution Of Wealth ◽  
Brazilian Northeast

O objetivo deste estudo foi estimar os riscos de chuvas extremas nas nove capitais do Nordeste brasileiro no período de 19910 a 2012. Devido chuvas extremas e ao mau uso do solo, os desastres naturais mais comuns nessas capitais são as inundações, os deslizamentos e os desabamentos. Os desabamentos são consequências da ineficiência do sistema de drenagem, da remoção indiscriminada da cobertura vegetal e do aumento da saturação de água no solo, que reduz sua resistência e provoca sua ruptura. Também, os desmoronamentos devem-se ao mau uso do solo, má distribuição de renda, falta de moradia digna e má qualidade da educação pública. As inundações são acumulações de lâminas de água que podem invadir o interior das edificações e causar transtornos para a mobilidade urbana de pedestres e veículos. Esses eventos dependem de medidas estruturais e não estruturais e não prescindem da boa educação dos habitantes urbanos.  O ajuste dos eventos extremos de chuvas à função distribuição de probabilidade de Gumbel possibilitou as estimativas dos riscos para uma específica magnitude de chuva.      ABSTRACT   The objective of this study was to estimate the risks of extreme rainfall in the nine capitals of the Brazilian Northeast in the period 19910-2012. Due to extreme rainfall and bad land use, the most common natural disasters in these capitals are floods, mudslides and landslides. Landslides are consequences of the inefficiency of the drainage system, the indiscriminate removal of the vegetation and increasing water saturation in the soil reduces its strength and causes rupture. Also, landslides are due to misuse of land, unequal distribution of wealth, lack of decent housing and poor quality of public education. Floods are accumulations of the water levels that can invade the interior of buildings and cause inconvenience to urban mobility of pedestrians and vehicles. These events depend on structural and non-structural measures and of the good education of urban dwellers. After the fit of extreme rain events the Gumbel probability distribution function can be possible to estimate the risks for a specific magnitude of rain. Keywords: Extreme rains, mudslides, landslides and floods   

AUTOMATIC WATER LEVEL MONITORING WITH IOT AND LPWAN

2019 ◽  
pp. 95-103
Author(s):  
Krum Videnov ◽  
Vanya Stoykova
Keyword(s):  
Water Level ◽  
Real Time ◽  
Early Warning ◽  
Water Sources ◽  
Water Levels ◽  
Water Level Fluctuations ◽  
Level Monitoring ◽  
Water Level Monitoring

Monitoring water levels of lakes, streams, rivers and other water basins is of essential importance and is a popular measurement for a number of different industries and organisations. Remote water level monitoring helps to provide an early warning feature by sending advance alerts when the water level is increased (reaches a certain threshold). The purpose of this report is to present an affordable solution for measuring water levels in water sources using IoT and LPWAN. The assembled system enables recording of water level fluctuations in real time and storing the collected data on a remote database through LoRaWAN for further processing and analysis.

Interaction between water pressure in the basal drainage system and discharge from an Alpine glacier before and during a rainfall-induced subglacial hydrological event

1997 ◽  
Vol 24 ◽  
pp. 288-292 ◽  
Author(s):  
Andrew P. Barrett ◽  
David N. Collins
Keyword(s):  
Water Level ◽  
Water Pressure ◽  
Drainage System ◽  
Water Levels ◽  
Drainage Network ◽  
Alpine Glacier ◽  
Hydraulic Conditions ◽  
Borehole Water ◽  
Progressive Growth ◽  
Resultant Increase

Combined measurements of meltwater discharge from the portal and of water level in a borehole drilled to the bed of Findelengletscher, Switzerland, were obtained during the later part of the 1993 ablation season. A severe storm, lasting from 22 through 24 September, produced at least 130 mm of precipitation over the glacier, largely as rain. The combined hydrological records indicate periods during which the basal drainage system became constricted and water storage in the glacier increased, as well as phases of channel growth. During the storm, water pressure generally increased as water backed up in the drainage network. Abrupt, temporary falls in borehole water level were accompanied by pulses in portal discharge. On 24 September, whilst borehole water level continued to rise, water started to escape under pressure with a resultant increase in discharge. As the drainage network expanded, a large amount of debris was flushed from a wide area of the bed. Progressive growth in channel capacity as discharge increased enabled stored water to drain and borehole water level to fall rapidly. Possible relationships between observed borehole water levels and water pressures in subglacial channels are influenced by hydraulic conditions at the base of the hole, distance between the hole and a channel, and the nature of the substrate.

scholarly journals Spatial distribution of water level impact to back-barrier bays

2018 ◽  
Author(s):  
Alfredo L. Aretxabaleta ◽  
Neil K. Ganju ◽  
Zafer Defne ◽  
Richard P. Signell
Keyword(s):  
Water Level ◽  
Sea Level ◽  
Water Levels ◽  
Analytical Models ◽  
Barnegat Bay ◽  
Sea Level Fluctuations ◽  
Flooding Hazard ◽  
Short Period ◽  
Inlet Geometry ◽  
Spatial Estimates

Abstract. Water level in semi-enclosed bays, landward of barrier islands, is mainly driven by offshore sea level fluctuations that are modulated by bay geometry and bathymetry, causing spatial variability in the ensuing response (transfer). Local wind setup can have a secondary role that depends on wind speed, fetch, and relative orientation of the wind direction and the bay. Inlet geometry and bathymetry primarily regulate the magnitude of the transfer between open ocean and bay. Tides and short-period offshore oscillations are more damped in the bays than longer-lasting offshore fluctuations, such as storm surge and sea level rise. We compare observed and modeled water levels at stations in a mid-Atlantic bay (Barnegat Bay) with offshore water level proxies. Observed water levels in Barnegat Bay are compared and combined with model results from the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) modeling system to evaluate the spatial structure of the water level transfer. Analytical models based on the dimensional characteristics of the bay are used to combine the observed data and the numerical model results in a physically consistent approach. Model water level transfers match observed values at locations inside the Bay in the storm frequency band (transfers ranging from 70–100 %) and tidal frequencies (10–55 %). The contribution of frequency-dependent local setup caused by wind acting along the bay is also considered. The approach provides transfer estimates for locations inside the Bay where observations were not available resulting in a complete spatial characterization. The approach allows for the study of the Bay response to alternative forcing scenarios (landscape changes, future storms, and rising sea level). Detailed spatial estimates of water level transfer can inform decisions on inlet management and contribute to the assessment of current and future flooding hazard in back-barrier bays and along mainland shorelines.

scholarly journals The effects of ENSO, climate change and human activities on the water level of Lake Toba, Indonesia: a critical literature review

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Hendri Irwandi ◽  
Mohammad Syamsu Rosid ◽  
Terry Mart
Keyword(s):  
Climate Change ◽  
Water Level ◽  
Human Activities ◽  
Southern Oscillation ◽  
Climatic Conditions ◽  
Water Levels ◽  
Dominant Factor ◽  
Climate Projections ◽  
Continuous Increase ◽  
The Future

AbstractThis research quantitatively and qualitatively analyzes the factors responsible for the water level variations in Lake Toba, North Sumatra Province, Indonesia. According to several studies carried out from 1993 to 2020, changes in the water level were associated with climate variability, climate change, and human activities. Furthermore, these studies stated that reduced rainfall during the rainy season due to the El Niño Southern Oscillation (ENSO) and the continuous increase in the maximum and average temperatures were some of the effects of climate change in the Lake Toba catchment area. Additionally, human interventions such as industrial activities, population growth, and damage to the surrounding environment of the Lake Toba watershed had significant impacts in terms of decreasing the water level. However, these studies were unable to determine the factor that had the most significant effect, although studies on other lakes worldwide have shown these factors are the main causes of fluctuations or decreases in water levels. A simulation study of Lake Toba's water balance showed the possibility of having a water surplus until the mid-twenty-first century. The input discharge was predicted to be greater than the output; therefore, Lake Toba could be optimized without affecting the future water level. However, the climate projections depicted a different situation, with scenarios predicting the possibility of extreme climate anomalies, demonstrating drier climatic conditions in the future. This review concludes that it is necessary to conduct an in-depth, comprehensive, and systematic study to identify the most dominant factor among the three that is causing the decrease in the Lake Toba water level and to describe the future projected water level.

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