Enhancing Flood Protection Strategies in Algeria through the Assessment of Maximum Discharge in Wadis

<p><span>The Surface Water and Ocean Topography CNES and NASA mission, planned for launch in late 2022, will provide a global mapping of the water surface elevation, width and slope of rivers wider than 100m worldwide. The estimation of discharge using solely the SWOT-type observations together with the existing satellite data has received a noticeable attention recently. The attempts to solve this problem have expectedly confirmed that it is ill posed and additional data could be needed, such as the estimates of the mean, minimum and maximum discharge from the available global scale hydrological databases. However, taking into account the accuracy of such estimates and the issue of their relevance to the study period, the problem remains challenging. We suggest a new estimation method, designed specially to reduce the solution bias. It combines Bayesian and Variational approaches to improve the algorithm robustness and stability. In this method the likelihood function is computed, allowing a useful analysis of equifinality often encountered in discharge estimation problems for ungauged basins. The algorithm is designed for global and/or basin-scale applications given the multi-level structure of the methodology. The latter involves different levels of complexity in terms of the representation of the flow dynamics and therefore different computational requirements. Here, we investigate discharge and bathymetry estimation under strong uncertainties from SWOT simulations and their combination with optical (Landsat and Sentinel 2) and altimetry (Jason, ENVISAT, Sentinel 3) data. The global application involves a Python low-cost algorithm that will be run globally through the Confluence platform implemented by UMass with the SWOT Science Team.</span></p><p><span>Keywords: Data assimilation, Bayesian estimation, remote sensing, SWOT, hydraulic modelling, discharge estimation, altimetry, optical imagery, rivers</span></p>

In this paper we focused on the history of floods and extreme flood frequency analysis of the upper Danube River at Bratislava. Firstly, we briefly describe the flood marks found on the Danube River in the region of Bratislava, Slovakia, and provide an account of the floods’ consequences. Secondly, we analyzed the annual maximum discharge series for the period 1876-2012, including the most recent flood of June 2013. Thirdly, we compare the values of T-year design discharge computed with and without incorporating the historic floods (floods of the years 1501, 1682, and 1787 into the 138-year series of annual discharge peaks). There are unfortunately only a few historic flood marks preserved in Bratislava, but there are very important and old marks in neighbouring Hainburg and other Austrian cities upstream to Passau. The calculated T-year maximum discharge of the Danube at Bratislava for the period 1876-2010 without and with historic flood values have been compared. Our analysis showed that without incorporating the historic floods from the years 1501, 1682, and 1787 the 1000-year discharge calculated only with data from the instrumented period 1876- 2013 is 14,188 m3 s-1, and it is lower compared to the 1000-year discharge of 14,803 m3 s-1 when the three historic floods are included. In general, the T-year discharge is higher throughout the whole spectrum of T-year discharges (10, 20, 50, 100, 200, 500-year discharge) when the three historic floods are included. Incorporating historic floods into a time series of maximum annual discharge seems to exert a significant effect on the estimates of low probability floods. This has important implications for flood managements and estimation of flood design discharge.

The occurrence of extreme floods in several river basins of the countries of Central and Eastern Europe over the last thirty years has drawn the attention of the public (as well as the competent authorities) to the problems of flood protection. Although the development and operational use of non-structural measures (such as flood forecasting and warning systems), represents one of the effective flood protection measures, the structural means (flood protection, levees, flood control reservoirs) are of great importance, too. Especially in the upper parts of the river basin, where the time between the detection of the causes of the flood (heavy rainfall) and its consequence (flood) is short and does not affect the effective protective activity (e.g. evacuation). Over the last 30 years, flood protections have been built along the Uh River (Slovakia, Ukraine) to protect the environment from floods. These dams adversely affected the storage capacity of water in the basin. This resulted in flood flows increase on the lower sections of the Uh River in Slovakia. These facts need to be demonstrated by the need to evaluate the proposed design values for those sections. The study presents an analysis of the long-term flood regime of the river Uh in the section Uzhhorod (Ukraine) - Lekárovce (Slovakia). The first part analyses the trend changes in the time series of maximum annual discharge Qmax in the stations Lekárovce and Uzhhorod on the basis of the observed Qmax data in these profiles (period 1931-2019). These Qmax series were subsequently used to estimate the maximum T-year discharge at the Lekárovce station for the changed conditions of the Uzhhorod - Lekárovce section. Using these derived data and the observed form of the summer flood hydrograph from July 1980, a 100-year flood scenario was developed for the Uh River in Lekárovce. The achieved results indicate a further increase in flood risk in Lekárovce.

In this study, the variations of rainfall and river discharges were analyzed in the Chenyulan watershed in Nantou County, central Taiwan. The hydrological data, including rainfall, daily discharges and yearly maximum instantaneous discharge, were collected from the Neimaopu hydrology station for the period from 1972 to 2022, covering approximately 50 years. According to the data analysis, when the rainfall exceeds the average, the river discharges in the Chenyoulan catchment increases, with larger rainfall events leading to more significant changes. Upon comparing the long-term data, it was found that the maximum instantaneous discharge occurred on August 1, 1996, during the Herb Typhoon. Though this event did not coincide with the historical maximum for total rainfall, rainfall intensity or average rainfall intensity, it resulted in the maximum instantaneous discharge.  All of the rainfall events, daily average discharge and yearly maximum instantaneous discharge are preliminarily analyzed as follows: 1. Rainfall in the catchment shows a positive correlation with river discharge; 2. The increase in rainfall characteristics in the catchment and the increase in discharge are not linearly related; 3. The non-linear reasons for the relationship between rainfall and maximum instantaneous discharge are preliminarily summarized as being related to soil conditions, different rainfall intensity locations and the runoff coefficients of various catchment units; 4. This study will subsequently estimate the average runoff coefficient of the catchment based on the relationship between individual rainfall and discharge, and conclude rational formula.

Changes in watershed land use are a concern due to the increase of flood from year to year which can harm the community both material and non-material. Meanwhile, during the dry season there was a significant decrease and causes irrigation water supply and clean water for daily needs to decrease and even to dry. Surface runoff and infiltration in a watershed area becomes an inseparable unit, with increasing surface runoff causing big flooding, flash floods and reducing infiltration, causing less groundwater supply to maintain river availability tend to decrease. The testing of vegetation effect on watershed areas on surface runoff and infiltration with a rainfall simulator was to analyze the extent of the role of vegetation in rainfall intensity with surface runoff and infiltration on rainfall intensity. Tests were carried out using a rain fall simulator using intensities I2 and I5 on two types of vegetation selected at the location of Maros watershed, namely mango and bamboo vegetation. The results show that changes in land cover increase surface runoff and reduce infiltration. So that land use should not be carried out carelessly and still have to pay attention to the sustainability of the function of the forest as river water retention. Land damage will be responded to by unexpected flooding and disruption of the land ecosystem, causing the extinction of flora and fauna habitat to become an indicator of increasingly critical land damage.

Extended Abstract Introduction:The erodibility of watershed area is a function of several factor, one of these factors is topography. Including main topography features is slope aspect of which directly or with the effect on other environmental factors is caused changes in soil hydrological processes particularly the potential for runoff and sediment production. Soil erosion is the most important environmental factor in the world that adversely affects all-natural ecosystems as well as those under human management. Although soil erosion has existed throughout history, it has been intensified in recent years due to improper land use. Environmental factors, such as climate situation, topography, soil, and land use affect sediment formation in watershed areas. Aghajari formation is among the most erodible in Iran. Aghajari formation, covered with Bakhtiari conglomerate, is located on Mishan marl formation. This marl formation was formed between Pliocene and Miocene. Aghajari formation consists of gray and brown calcareous sandstone, gypsum red marl, and siltstone. Its main section spreads from Omidiyeh to the Aghajari oil field and it has a thickness of 2965 meters. The presence of gypsum marls has made Aghajari formation apt to erosions of different kinds, especially surface erosion, rill erosion, badland, and mass movement. One of the most eridibility of Iran is the Gahsaran formation. Gahsaran formation has oil industries that yearly thousands of tons of sulfur and carbon dioxide interpolate into the air. And it can be caused by acidic rainfall. Thus investigating the role of acidic rainfall on soil erosion and sediment production in these areas is necessary. Gahsaran formation has a thickness of about 1600 meters. A viewpoint of lithology is consisting of salt, anhydrite, colorful lime, and some shale. Gahsaran formation age is lower Miocene.Materials and methods:In this investigation in order to investigate sensitivity to the erosion and sediment yield the main aspect of slope of Aghajari and Gachsaran formation deposits, part of margha and kuhe gach watershed areas in Izeh Township respectively with the area of 1202 and 1609 hectares was elected. In this investigation in order to determine productivity runoff and sediment in 8 points and with 3 replicates in Gachsaran formation and in 8 points and with 3 replicates in Aghajari replicates in rainfall intensities 1 and 1/25 mm in min in 4 slope aspect; northern, southern, eastern and western with using of kamphorst rain simulator was done. In order to analyze statistical from SPSS and EXCELL was used. The study utilized the Kamphorst rainfall simulator. This fully standardized, easily portable rainfall simulator was designed to cover a plot area of 625 cm2. The rainfall simulator is used to determine the characteristics of soil, erosion, water infiltration, and is also suitable for soil research. It is a standard method to use it to determine the erodibility of surface deposits. The experimental plot area of 625 cm2 with a smooth gradient was selected, which was the representative of the main slope aspects. Meanwhile, the Kamphorst rainfall simulator was installed at the height of 200 cm to reach to raindrop boundary velocity.Results and discussion:The highest of sediment rate in both Gachsaran and aghajari formations in rainfall intensities 1, 1/25 mm in min is belonged to eastern slope aspects. The highest of runoff rate in aghajari formation is belonged to northern slope aspect and in Gachsaran formation is belonged to southern slope aspect. There was a significant difference in the south-east, south-west slopes in comparison of the amount of sediment produced in different aspects of the slope in the Aghajari Formation at the intensity of 1 mm/min. But, there was a significant difference in the amount of runoff produced and permeability of north-west slopes. And at 1.25 mm/min intensity, sediment production in south-east and south-west slopes showed a significant difference. But runoff was significantly different in north-south, north-east and north-west slopes. In terms of sediment production in Gachsaran and Aghajari formations, the total rate was highest at two intensities of 1 and 1.25 mm/min in the eastern slope. But, in terms of runoff in Aghajari Formation, the northern slopes have the highest runoff and in Gachsaran Formation, the southern slopes have the highest runoff. And, in terms of permeability in Aghajari Formation, the southern slopes and in the Gachsaran Formation, the western slopes have the highest penetration rate in the two intensities.Conclusion:The rate of productivity sediment also in Aghajari formation in both mentioned intensities is more than Gachsaran formation. But the rate of productivity runoff in mentioned intensities in Gachsaran formation is more than Aghajari formation. The rate of changes in productivity sediment and runoff in various slope aspects in both formations also significance difference showed.Key words: Soil erosion, Sediment production, Aghajari formation, Rain simulator, Gachsaran formationConclusion:The rate of productivity sediment also in Aghajari formation in both mentioned intensities is more than Gachsaran formation. But the rate of productivity runoff in mentioned intensities in Gachsaran formation is more than Aghajari formation. The rate of changes in productivity sediment and runoff in various slope aspects in both formations also significance difference showed.Key words: Soil erosion, Sediment production, Aghajari formation, Rain simulator, Gachsaran formationConclusion:The rate of productivity sediment also in Aghajari formation in both mentioned intensities is more than Gachsaran formation. But the rate of productivity runoff in mentioned intensities in Gachsaran formation is more than Aghajari formation. The rate of changes in productivity sediment and runoff in various slope aspects in both formations also significance difference showed.Key words: Soil erosion, Sediment production, Aghajari formation, Rain simulator, Gachsaran formationConclusion:The rate of productivity sediment also in Aghajari formation in both mentioned intensities is more than Gachsaran formation. But the rate of productivity runoff in mentioned intensities in Gachsaran formation is more than Aghajari formation. The rate of changes in productivity sediment and runoff in various slope aspects in both formations also significance difference showed.Key words: Soil erosion, Sediment production, Aghajari formation, Rain simulator, Gachsaran formationKey words: Soil erosion, Sediment production, Aghajari formation, Rain simulator, Gachsaran formation

With regard to minimizing flood damage, there are measures of different character each of which has its justification and plays an important role in flood protection. Implementation of traditional flood protection measures is still very important; however, an increasing role should be played particularly by flood prevention and flood risk management. The paper presents a case study on flood hazard and flood risk assessment at the local spatial scale using geographic information systems, remote sensing, and hydraulic modelling. As for determining flood hazard in the model area, which has 3.23 km2, the estimation of maximum flood discharges and hydraulic modelling were important steps. The results of one-dimensional hydraulic modelling, which are water depth and flow velocity rasters, were the basis for determining flood hazard and flood risk. In order to define flood risk, the following steps were applied: determining flood intensity on the basis of water depth and flow velocity rasters, determining flood hazard using three categories (low, medium, and high) based on flood intensity, defining vulnerability for the classes of functional areas using three categories of acceptable risk (low, medium, and high), and lastly determination of flood risk which represents a synthesis of flood hazard and vulnerability of the model area.

Water scarcity, unequal access to water resources, and the impact of climate change on water availability are among the major global environmental concerns. As dynamic and vulnerable water subjects, rivers are constantly exposed to the pressure of natural conditions variability (primarily climatic) and direct anthropogenic influences. Therefore, it is necessary to investigate river regime dynamics over longer periods to adapt the water management sector, and human demands to any observed variations in river discharge. Observing the periodicity or cyclicity of the occurrence of certain discharge values is an important topic of modern physical geography and hydrology research. Statistics and hydrologic modelling provide great opportunities for observing cyclicality and forecasting future trends. The aim of this paper is to indicate the importance of specific statistical methods of autocorrelation and spectral analysis to study the repeatability of mean annual and maximum discharges. The South Morava River in Serbia (HS: Mojsinje, Korvingrad, Grdelica) has been selected as a case study. The obtained results (period: 1924-2021) indicated the significant cyclicity of mean annual discharges, especially pronounced at the upstream hydrological station Grdelica (3.5-year cycle) and downstream hydrological station Mojsinje (19.5-year cycle). These cyclicities are mostly influenced by variations in the amount of precipitation received from the upper part of the river basin (R > 0.6). In contrast, no regular cycles of maximum annual discharge values were determined in the studied period. The obtained results can be important for future detailed geographic and hydrologic studies as well as for the development of strategies and plans in the field of water management, environmental protection, spatial planning, prevention of floods and droughts, etc.

One of indicators which represent watershed condition is hydrology condition that can be represented by the value of monthly discharge, maximum discharge, minimum discharge, and river regime coefficient. This study aims to estimate the monthly discharge value of Sei Petani Sub-Watershed using the Mock Hydrology Model. The application of the Mock Model require some input data such as rainfall, climate data, and area of watershed. Optimum parameters could be obtained by model calibration and validation that was carried out by statistical and graphical test. Optimal parameters that has been obtained would be used to estimate discharge value in existing condition. The result showed that the model accuration for calibration and validation process has the coefficient correlation (R) value more than 0.75, with volume error (VE) less than 0.05 that means there were strong relationship among calculated data and observed data. The optimum parameters value accomplished to estimating discharge value for existing condition. The watershed health based on hydrology indicators on Sei Petani Subwatershed could be seen with the value of specific maximum discharge, specific minimum discharge, and river regime coefficient that shown this watershed in well condition.

Formulation of a country’s flood protection s trategy in every case depends on the technical-socio-economic conditions of the given country. The flood safety requirements are highly influenced by the country’s performance and financial situation. On the Hungarian rivers, flood safety is based on the 100-year return period maximum flood events and the flood safety requirements must be developed accordingly. The state must guarantee the success of the flood protection up to this flood safety level. The water management sector has also formed the Hungarian flood protection strategy to this flood safety level as an operator of primary flood protection structures. In the past decades, due the changes in socio-economic conditions and the rise of extremities caused by climate change have caused that flood protection strategy had to be changed several times. In my article I show the changes and the effects of changes on the operational flood protection activities and preventive flood protection strategy.

Este trabalho trata da aplicação de um modelo hidrológico que transforma chuva em vazão, atrelado àutilização de técnicas de tratamento de dados em ambiente SIG, para quantificar e representar a distribuiçãoespacial dos componentes hidrológicos de uma bacia hidrográfica de médio porte. O modelo hidrológico que tempor base a análise dos efeitos dos impactos da urbanização sobre o sistema de drenagem, utiliza a técnica dequantificação de áreas impermeáveis e da representação das características superficiais do terreno para simularpicos de vazão de cheias, em bacias hidrográficas urbanas a parcialmente urbanizadas. Para a quantificaçãodas áreas impermeáveis foram confeccionadas cartas temáticas da cobertura superficial do terreno através detécnicas de fotointerpretação digital. O aumento do escoamento superficial e do pico de vazão de cheias foramquantificados a partir da aplicação da fórmula racional, modificada e adaptada para bacia de médio porte. Paratais cálculos, foi necessário definir alguns parâmetros hidrológicos tais como intensidade da chuva, tempo deconcentração, grupos hidrológicos de solos, coeficiente de retardo por armazenamento e o coeficiente de escoamentosuperficial do terreno. Todos os parâmetros considerados foram analisados em conjunto e integradosem ambiente SIG, tendo como resultado final, a quantificação dos coeficientes de escoamento superficial e aanálise dos picos de vazão de cheias, dentro de uma visão multitemporal e de uma projeção futura. O procedimentometodológico desenvolvido provou ser uma boa alternativa para a distribuição espacial dos parâmetroshidrológicos e da estimativa de vazão de cheias em bacias hidrográficas de médio porte, que não possuam dados fluviométricos.

Abstract. The Volcán de Colima, one of the most active volcanoes in Mexico, is commonly affected by tropical rains related to hurricanes that form over the Pacific Ocean. In 2011, 2013 and 2015 hurricanes Jova, Manuel and Patricia, respectively, triggered tropical storms that deposited up to 400 mm of rain in 36 h, with maximum intensities of 50 mm h −1. The effects were devastating, with the formation of multiple lahars along La Lumbre and Montegrande ravines, which are the most active channels in sediment delivery on the south-southwest flank of the volcano. Deep erosion along the river channels and several marginal landslides were observed, and the arrival of block-rich flow fronts resulted in damages to bridges and paved roads in the distal reaches of the ravines. The temporal sequence of these flow events is reconstructed and analyzed using monitoring data (including video images, seismic records and rainfall data) with respect to the rainfall characteristics and the hydrologic response of the watersheds based on rainfall-runoff numerical simulation. For the studied events, lahars occurred 5–6 h after the onset of rainfall, lasted several hours and were characterized by several pulses with block-rich fronts and a maximum flow discharge of 900 m3 s −1. Rainfall-runoff simulations were performer using the SCS-curve number and the Green–Ampt infiltration models, providing a similar result in the detection of simulated maximum watershed peaks discharge. Results show different behavior for the arrival times of the first lahar pulses that correlate with the simulated catchment's peak discharge for La Lumbre ravine and with the peaks in rainfall intensity for Montegrande ravine. This different behavior is related to the area and shape of the two watersheds. Nevertheless, in all analyzed cases, the largest lahar pulse always corresponds with the last one and correlates with the simulated maximum peak discharge of these catchments. Data presented here show that flow pulses within a lahar are not randomly distributed in time, and they can be correlated with rainfall peak intensity and/or watershed discharge, depending on the watershed area and shape. This outcome has important implications for hazard assessment during extreme hydro-meteorological events, as it could help in providing real-time alerts. A theoretical rainfall distribution curve was designed for Volcán de Colima based on the rainfall and time distribution of hurricanes Manuel and Patricia. This can be used to run simulations using weather forecasts prior to the actual event, in order to estimate the arrival time of main lahar pulses, usually characterized by block-rich fronts, which are responsible for most of the damage to infrastructure and loss of goods and lives.

The development and management of irrigation, drainage and flood protection schemes are confronted with rapidly changing conditions, especially in the least and emerging developing countries. Issues at stake are the need to increase food production significantly, the development of water shortages, pollution of water resources, the increased requirement for flood management and flood protection schemes, the need for sustainable development and possible impacts of climate changes.In this paper focus is on how these issues may play a role in the development of irrigation, drainage and flood protection measures and schemes under different climatological and socio‐economic conditions. In line with this the Strategy for Action of the International Commission on Irrigation and Drainage (ICID) is presented, showing the contributions the ICID is making in answer to these challenges. Copyright © 2001 John Wiley & Sons, Ltd.

Over-the-horizon (OTH) radar uses the refractive properties of high-frequency radiowave propagation through the ionosphere for wide-area surveillance at long ranges. Ionospheric propagation often gives rise to multiple raymodes between the OTH radar and a target which results in multiple slant tracks from a single target. Multipath and multiple target ambiguities are typically resolved by assuming that the down-range ionosphere is known precisely and then using ray tracing to determine the coordinate registration (CR) transformations from slant coordinates to target locations in ground coordinates. To achieve greater robustness to the uncertainty in down-range ionospheric conditions, this paper presents a maximum a posteriori (MAP) mode linking method for track association that employs statistical modeling of the down-range plasma frequency profile and corresponding multipath slant track measurements. To determine the statistical model parameters from quasi-vertical incidence (QVI) ionogram and wide-sweep backscatter ionogram (WSBI) measurements, the plasma frequency profile is approximated as a homogeneous random process over the region near the mid-point between the radar and the dwell illumination region. Using samples of a 3-D ionospheric model fitted to the and QVIs and WSBIs, statistical propagation model parameters are obtained by smoothed bootstrap resampling combined with Monte Carlo evaluation of a ray tracing propagation model. Simulation results indicate that the MAP mode linking method can achieve nearly a 3:1 improvement in ground coordinate accuracy over conventional mode linking methods with much higher probabilities of correct raymode identification and slant-track-to-target assignment. Real data results from roughly 90 minutes of OTH radar slant track data demonstrate that the MAP mode linking method can provide as much as a 4:1 improvement in ground coordinate accuracy over conventional methods.

An innovative soft water level sensor is proposed to characterize the hydrological behaviour of agricultural catchments by measuring rainfall and stream flows. This sensor works as a capacitor coupled with a capacitance to frequency converter and measures water level at an adjustable time step acquisition. It was designed to be handy, minimally invasive and optimized in terms of energy consumption and low-cost fabrication so as to multiply its use on several catchments under natural conditions. It was used as a stage recorder to measure water level dynamics in a channel during a runoff event and as a rain gauge to measure rainfall amount and intensity. Based on the Manning equation, a method allowed estimation of water discharge with a given uncertainty and hence runoff volume at an event or annual scale. The sensor was tested under controlled conditions in the laboratory and under real conditions in the field. Comparisons of the sensor to reference devices (tipping bucket rain gauge, hydrostatic pressure transmitter limnimeter, Venturi channels…) showed accurate results: rainfall intensities and dynamic responses were accurately reproduced and discharges were estimated with an uncertainty usually acceptable in hydrology. Hence, it was used to monitor eleven small agricultural catchments located in the Mediterranean region. Both catchment reactivity and water budget have been calculated. Dynamic response of the catchments has been studied at the event scale through the rising time determination and at the annual scale by calculating the frequency of occurrence of runoff events. It provided significant insight into catchment hydrological behaviour which could be useful for agricultural management perspectives involving pollutant transport, flooding event and global water balance.