Modeling interactions between tides, storm surges, and river discharges in the Kapuas River delta

The Kapuas River delta is a unique estuary system on the west coast of Borneo Island, Indonesia. Its hydrodynamics is driven by an interplay between storm surges, tides, and rivers discharge. These interactions are likely to be exacerbated by global warming, leading to more frequent compound flooding in the area. The mechanisms driving compound flooding events in the Kapuas River Delta remain, however, poorly known. Here we attempt to fill this gap by assessing the interactions between river discharges, tides, and storm surges and how they can drive a compound inundation over the riverbanks, particularly within Pontianak, the main city along the Kapuas River. We simulated these interactions using the multi-scale hydrodynamic model SLIM. Our model correctly reproduces the Kapuas River’s hydrodynamics and its interactions with tides and storm surge from the Karimata Strait. We considered several extreme scenario test cases to evaluate the impact of tide-storm-discharge interactions on the maximum water level profile from the river mouth to the upstream part of the river. Based on the maximum water level profiles, we could divide the main branch of the Kapuas River’s stream into three zones, i.e., the tidally-dominated region (from the river mouth to about 4 km upstream), the mixed-energy region (from about 4 km to about 30 km upstream) and the river-dominated region (beyond 30 km upstream). Thus, the local water management can define proper mitigation for handling compound flooding hazards along the riverbanks by using this zoning category. The model also successfully reproduced a compound inundation event in Pontianak, which occurred on 29 December 2018. For this event, the wind-generated surge appeared to be the dominant trigger.

Identification of Marine Debris and Its Distribution Using Unmanned Aerial Vehicle (UAV) on the Cirebon Coastal Area, Indonesia

Marine debris can be a significant problem when it enters the ocean. One of the areas, which has a marine debris problem is Cirebon Coast. Such a problem occurs due to the high human population and activities in this particular coastal area. An effective cleaning method is required to prevent this problem. However, to determine the cleaning method, comprehensive information about the debris condition is required. Therefore, this study aims to identify the dominant types of marine debris and analyze the effect of tides on the characteristics and distribution of debris on the Cirebon Coast. This study carried out marine debris identification by orthophoto obtained from a DJI Phantom 4 Pro Unmanned Aerial Vehicle (UAV)/drone. The dominant types of marine debris on the Cirebon Coast are plastic and styrofoam. Based on the aerial imagery validation results, plastic and styrofoam larger than Ground Sample Distance (GSD) are easily detected. Visually, debris in Karang Anom more than in Rawa Urip. The change in tidal height can affect debris not visible on the orthophoto at the maximum water level. In addition, the tides can also move marine debris varying from 10 to 50 cm from its previous position. The debris area at Rawa Urip Beach when slack before flood tide (55.53 m2) is larger than the area when slack before ebb tide (52.71 m2). The debris area at Karang Anom Beach at low tide (129.89 m2) is larger than when slack before ebb tide (75.79 m2). This study revelaed that the factors affecting debris area on the Cirebon Coast comprise tidal height, seawater visibility, and the beach structure (slope and coast components).

Phreatic Surface Estimation In MSE Wall With Geocomposite Back Drainage

This study proposes a simple mathematic model for approximating the level of phreatic surface inside the protected zone in mechanical stabilized earth wall with back drain installation though the position of phreatic surface at the drainage interface (ho) which reflects the maximum level of phreatic surface in the protected zone. The proposed model was established based on dataset taken from 180 simulation cases caried out in Plaxis environment. Regression results present a combination of significant effects and major role to maximum water level in the protected zone (ho) of a ratio of length from upstream water to the drainage face to the wall height (L/H), a soil permeabilities coefficient (k) and a transmissivity of the drainage material (Tnet). The proposed model can facilitate design of drainage material to achieve desired level of phreatic surface in the protected zone.

Geo-spatial Analysis of Farmland Affected by 2020 Flooding of River Rima, Northwestern Nigeria

The flooding of River Rima is an annual issue affecting farmland located within the floodplains. This phenomena causes loss of farm produce and mass destruction of buildings, including roads and bridges in the area. Estimating the farmland affected by the flood will help the policy makers in decision making on how to mitigate the impact of flooding in the affected areas. The Terra/MODIS satellite image with 7-2-1 bands combination was used to classify the image into four landcover types. The area covered by flood was selected to calculate the flood area using Image Calculator module on QGIS software. The class of water was imposed on Digital Elevation Model that was obtained from Environmental Monitoring Satellite called The Shuttle Radar Topography Mission (SRTM). The result shows that River Rima flood occupies about 17,517 km2, equivalent to 1.7 million hectares of farmland that is below 230 meters (ASL). It was recommended that the local authorities and decision makers may use the flood map to showing flood risk zones so as to deter construction beyond the buffer. Farmers should adhere strictly to NiMet’s advice based on flood predictions. The civil engineers should also take note of the maximum water level during flooding so as to apply professional advice when constructing roads and bridges in the area.

Angka Keamanan Piping di Bawah Tubuh Bendungan dengan Metode Harza

Dams have many benefits such as irrigation, flood prevention, power generation and even tourism, especially in areas where the dam is located. So that the benefits received can last a long time, in the planning, it must be analyzed for stability, seepage discharge that occurs and the safety of the piping. The piping hazard safety figures in this study were calculated using the Harza method for maximum water level conditions, normal water levels, fast receding and empty dams at sta 0 + 150, sta 0 + 200, sta 0 + 250 and sta 0 + 300. Based on the calculation results, it is found that the safety of piping hazards without filters with the grouting method do not meet the requirements safety factor, especially in conditions of maximum water level, normal water level and fast receding. In order for the safety of piping hazard in order to meet the requirements, a filter is applied under the dams. The filter is applied so that the piping hazard safety figure meets the requirements of all water level conditions and all station is 80 cm deep. Keywords: safety factor, piping, Harza method, filter ABSTRAK Bendungan memiliki banyak manfaat seperti irigasi, pencegah banjir, pembangkit listrik bahkan pariwisata khususnya pada wilayah dimana bendungan tersebut berada. Agar manfaat yang diterima dapat berlangsung lama maka dalam perencanaannya wajib dianalisis terhadap stabilitas, debit rembesan yang terjadi maupun keamanan dari piping. Angka keamanan bahaya piping pada penelitian ini dihitung dengan menggunakan metode Harza untuk kondisi muka air maksimum, muka air normal, surut cepat dan bendungan kosong di sta 0+150, sta 0+200, sta 0+250 serta sta 0+300. Berdasarkan hasil perhitungan didapatkan bahwa angka keamanan bahaya piping tanpa penggunaan filter dengan metode grouting tidak memenuhi persyaratan angka keamanan khususnya pada kondisi muka air maksimum, muka air normal dan surut cepat. Agar angka keamanan bahaya piping memenuhi persyaratan maka diaplikasikan filter dibawah tubuh bendungan. Filter yang diaplikasikan agar angka keamanan bahaya piping memenuhi persyaratan diseluruh kondisi muka air dan seluruh sta adalah dengan kedalaman 80 cm. Kata kunci: angka keamanan, piping, metode Harza, filter Abstract Dams have many benefits such as irrigation, flood prevention, power generation and even tourism, especially in areas where the dam is located. So that the benefits received can last a long time, in the planning, it must be analyzed for stability, seepage discharge that occurs and the safety of the piping. The piping hazard safety figures in this study were calculated using the Harza method for maximum water level conditions, normal water levels, fast receding and empty dams at sta 0 + 150, sta 0 + 200, sta 0 + 250 and sta 0 + 300. Based on the calculation results, it is found that the safety of piping hazards without filters with the grouting method do not meet the requirements safety factor, especially in conditions of maximum water level, normal water level and fast receding. In order for the safety of piping hazard in order to meet the requirements, a filter is applied under the dams. The filter is applied so that the piping hazard safety figure meets the requirements of all water level conditions and all station is 80 cm deep. Keywords: safety factor, piping, Harza method, filter ABSTRAK Bendungan memiliki banyak manfaat seperti irigasi, pencegah banjir, pembangkit listrik bahkan pariwisata khususnya pada wilayah dimana bendungan tersebut berada. Agar manfaat yang diterima dapat berlangsung lama maka dalam perencanaannya wajib dianalisis terhadap stabilitas, debit rembesan yang terjadi maupun keamanan dari piping. Angka keamanan bahaya piping pada penelitian ini dihitung dengan menggunakan metode Harza untuk kondisi muka air maksimum, muka air normal, surut cepat dan bendungan kosong di sta 0+150, sta 0+200, sta 0+250 serta sta 0+300. Berdasarkan hasil perhitungan didapatkan bahwa angka keamanan bahaya piping tanpa penggunaan filter dengan metode grouting tidak memenuhi persyaratan angka keamanan khususnya pada kondisi muka air maksimum, muka air normal dan surut cepat. Agar angka keamanan bahaya piping memenuhi persyaratan maka diaplikasikan filter dibawah tubuh bendungan. Filter yang diaplikasikan agar angka keamanan bahaya piping memenuhi persyaratan diseluruh kondisi muka air dan seluruh sta adalah dengan kedalaman 80 cm. Kata kunci: angka keamanan, piping, metode Harza, filter

Slope Stability Analysis of Haditha Dam after Earthquake using Geo-Studio Software

The current study is designed to analyze theslope stability of Haditha damwhich is an earth-fill dam constructed on the Euphrates River in the middle-west of Iraq. Finite element modeling was used in the present study to analyze the combined seepage and post-earthquake slope stability of Haditha earth dam. The maximum water level of a steady seepage case was considered to evaluate seepage. - Three different water levels (maximum, normal, and minimum) were applied, and nine different equilibrium slope stability limits were used to analyze the upstream and downstream slopes of the dam with three horizontal maximum accelerations.The input data given to the software are the dam geometry and its material properties with the earthquake records in the year2019.The dam was investigated by considering the water in the reservoir to be at maximum, minimum and normal water levels in its actual design. It was concluded that the dam is on the safe side in terms of stability even though the change in the earthquake's conditions in Iraq.

Forecasting annual maximum water level for Negro River at Manaus

<p>Variations in water levels of the Negro River, that flows through the Port of Manaus, can cause considerable regional environmental and socio-economic losses. It is therefore critical to advance predictions for water levels, especially flood levels, to provide more effective and earlier warnings to safeguard lives and livelihoods. Variations in water levels in free-flowing river systems, like the Negro follow large-scale precipitation anomalies, which offers an opportunity to predict maximum water levels using observed antecedent rainfall. This study aims to improve the performance and extend the lead time of statistical forecasts for annual maximum water level of the Negro River at Manaus, relative to operational forecasts. Multiple linear regression methods are applied to develop forecast models, that can be issued in March, February and January, with the best possible combinations potential predictors: observed antecedent catchment rainfall and water levels, large-scale modes of climate variability and the linear trend in water levels. Our statistical models gain one month of lead time against existing models, but are only moderately better than existing models at similar lead time. Using European Centre for Medium-Range Weather Forecasts (ECMWF) seasonal reforecast data with our statistical models, further gains an additional month of lead time of skilful performance. Our models lose performance at longer lead times, as expected. Our forecast models can issue skilful operational forecasts in March or earlier and have been successfully tested for operational forecast of 2020. This method can be applied to develop statistical models for annual maximum water level over other free-flowing rivers in the Amazon basin with intact catchments and historical water level record.</p>

Reduce the intensity of siltation of bulk reservoirs for irrigation and hydropower purposes

The results of field studies to study the siltation of a reservoir and the dynamics of their siltation are presented. The article presents designs that allow reducing the amount of sediment entering the reservoir bowl. The structure will contain spillways located perpendicular to the bed of the supply channel, elements of connecting structures, a sediment storage facility, and a lateral water outlet to the sediment storage facility. The reservoir sediment has a mark below the bottom of the supply channel and above the maximum water level in the reservoir and a wall of large pebbles that act as a filter for residual turbid water in the channel. In the basin of the deposit storage, a road is provided for trucks and equipment to carry out its seasonal cleaning.

Sea-level rise impacts on the tides of the European Shelf: mechanisms analysis

<p>Sea-level rise (SLR) can modify not only total water levels, but also tidal dynamics. Several studies have investigated the effects of SLR on the tides of the western European continental shelf (mainly the M2 component). Idier et al. (2017) further investigate this issue using a modelling-based approach, considering uniform SLR scenarios from −0.25 m to +10 m above present-day sea level. Assuming that coastal defences are constructed along present-day shorelines, the patterns of change in high tide levels (annual maximum water level) are spatially similar, regardless of the magnitude of sea-level rise (i.e., the sign of the change remains the same, regardless of the SLR scenario) over most of the area (70%). These changes are generally proportional to SLR, as long as SLR remains smaller than 2 m. Depending on the location, they can account for +/−15% of regional SLR. Changes in high tide levels are much less proportional to SLR when flooding is allowed, in particular in the German Bight. However, some areas (e.g., the English Channel) are not very sensitive to this option, meaning that the effects of SLR would be predictable in these areas, even if future coastal defence strategies are ignored.</p><p>In the present work, we focus on the mechanisms driving these tide changes, especially the bed friction damping, the resonance properties and the reflection at the coast, i.e., local and non-local processes. Additional simulations are done to quantify the effect of these mechanisms on tide changes.</p><p> </p><p>Reference: Idier D., Paris F., Le Cozannet G., Boulahya F., Dumas F. (2017) Sea-level rise impacts on the tides of the European Shelf. Continental Shelf Research, 137, 56-71.</p>