Undercut Banks Research Articles

Same streams in a different forest? Investigations of forest harvest legacies and future trajectories across 30 years of stream habitat monitoring on the Tongass National Forest, Alaska.

The effects of timber harvest practices and climate change have altered forest ecosystems in southeast Alaska. However, quantification of patterns and trends in stream habitats associated with these forests is limited owing to a paucity of data available in remote watersheds. Here, we analyzed a 30-year dataset from southeast Alaska's Tongass National Forest to understand how these factors shape stream habitats. First, we examined differences between broad management classes (i.e., harvested and non-harvested) that have been used to guide stream channel restoration goals. Second, we assessed associations between intrinsic landscape characteristics, watershed management, and timber harvest legacies on aquatic habitat metrics. And third, we examined trends in stream habitat metrics over the duration of the dataset to anticipate future management challenges for these systems. Small effect sizes for some harvest-related predictors suggest that some stream habitat metrics, such as pool densities, are less responsive than others, and management practices such as protecting riparian buffers as well as post-harvest restoration may help conserve fish habitats. Large wood densities increased with time since harvest at sites harvested >50 years ago, indicating that multiple decades of post-harvest forest regrowth may contribute large wood to streams (possibly alder), but that it is not enough time for old-growth trees (e.g., spruce, Picea, or hemlock, Tsuga,), classified as key wood, to develop and be delivered to streams. The declining trend in key wood (i.e., the largest size class of wood) regardless of management history may reflect that pre-harvest legacy old-growth trees are declining along streams, with low replacement. The introduction of wood to maintain complex stream habitats may fill this gap until riparian stands again contribute structural key wood to streams. Trend analyses indicate an increasing spatial extent of undercut banks that may also be influenced by shifting hydrologic regimes under climate change.

GEOLOGIA, MINERALOGIA, GEOQUÍMICA, FERTILIDADE E POTENCIAIS IMPACTOS AMBIENTAIS EM PRAIAS, BARRANCOS E ÁGUAS FLUVIAIS E LACUSTRES (BACIAS DOS RIOS PURUS E JURUÁ) NO ESTADO DO ACRE: TEXTO DE APRESENTAÇÃO

This text explains why the results of research carried out in the State of Acre in the years 2002 to 2008 were released late, with financial support from two research projects financed by the CNPQ (SelenMerAs and Geosedintama) and a third (Ageopam) which also had a slight facet towards the region of this State. Although several works were published through communications at events and journals, much was restricted to dozens of dissertations, TCCs and reports from IC/PIBIC and others. It was concluded that even after almost 20 years, it was still opportune to disseminate these results and discussions, mainly because they are focused on the geological, mineralogical, multi-element chemical and fertility characterization of sediments on river cliffs, beach sands (bars in Pontal) and suspended sediments from rivers and lakes, in addition to environmental impacts, mainly on the wave of mercurial problem announced loudly in those years, which covered the entire Amazon. The BOMGEAM bulletin was chosen to disseminate unpublished results, due to its low cost, speed and accessibility. There will be two issues dedicated to the topic: BOMGEAM – ACRE 1 and BOMGEAM – ACRE 2. Issue 1 is dedicated more to the geology, mineralogy and geochemistry of sediments in ravines and bars; and number 2 to sediment fertility and potential environmental impacts. There are 13 contributions, involving dissertations, TCCs and monographs from IC/PIBIC and PDR.

Evaluation of speculated reproductive habitat for Somatochlora calverti (Corduliidae), a rare and range-restricted dragonfly

Globally, freshwater ecosystems and the organisms that depend on them are at risk. Dragonflies and damselflies (collectively, “odonates”) have a history of being used as bioindicators of freshwater habitat quality due to their wide range in environmental sensitivities across species and because they are relatively accessible. However, the nymphal stage is severely understudied compared to the adult stage, which inhibits conservation efforts. Somatochlora calverti is a rare species of dragonfly in the family Corduliidae; members of the genus Somatochlora are notoriously difficult to find and collect in the field as nymphs and adults. Somatochlora calverti is known primarily from the Florida panhandle but has been documented in Alabama, Georgia, and South Carolina. The nymph of this species is speculated to use seepage streams analogous to sympatric congeners; however, the nymph has never been collected in the field and, therefore, its specific microhabitat is unknown. We conducted a review from a suite of informational sources to generate a holistic consensus on what is defined to be suitable reproductive habitat for S. calverti. Sources identified eight major environmental characteristics that are likely to harbor S. calverti: shallow seepage streams, including steephead ravines, with undercut banks and mats of Sphagnum moss adjacent to intact sandhill forest. These ecosystems are being lost and degraded by anthropogenic activity, which has considerable impacts on the persistence of habitat specialists, including S. calverti, and managers’ ability to conserve them.

The Relationship of Physical Properties of Rock to The Slope Stability of The Progo River Cliff in Sentolo-Sedayu, Kulon Progo, Yogyakarta, Indonesia

To support the increasingly advanced development of the Kulon Progo area, road access via the Progo River bridge needs to be maintained in instability. To support this, an engineering geological survey was carried out to find out the relationship between the physical properties of rocks and the stability of slopes on the cliffs of the Progo River. The research method begins with a field survey to obtain lithology and slope geometry data. Scanlines at selected locations were carried out to determine discontinuity areas and interpret rock weathering using a Schmidt hammer. Physical laboratory tests are useful for determining the bulk density and porosity of rocks, while from rock mechanical tests (shear strength) cohesion and friction angle values are obtained. The results of the safety factor analysis using the Slide program show that the slopes generally have a medium-high level of severity (Fk 1.2), supported by quite a lot of joint areas, varying porosity (4.12 – 25.10%) and the level of weathering is at level III-IV. Rock porosity is less related to slope strength, while weathering generally reduces slope stability.

Assistance in Designing Citarum River Cliff Protection to Control River Erosion in Atirompe Village, Majalaya District, Bandung Regency

Rivers are often used as a water source for agriculture, transportation, and water supply needs. One of the causes of riverbanks' damage is scouring the cliff's foot, which cannot withstand scouring currents. If not addressed immediately, it will cause more severe damage. Citarum River is one river that passes through Atirompe Village, Majalaya District. The riverbanks in the area have a risk of cliff failure. The study objective was to analyze the problem, design the protection, and calculate the budget. The hydrology and riverbank analysis of the Majalaya River has been performed. The steps are important to analyze the depth and width of the scour caused by the flow of the Citarum River water. Sediment data were collected at three locations, namely the upstream, middle, and downstream of the river segment that will be reviewed. In data processing, to obtain a sediment rating curve, it is necessary to measure the flow velocity, which will later be calculated and used as the flow rate that flows during TSS data collection. Using the HEC – RAS 6.2 software, the calculations with the Ripley Equation were compared to obtain the scour depth. For the design alternative, constructing a steel sheet pile-type cliff protection structure is one form of planning to protect riverbanks. This study also analyzes the recapitulation of the budgeting for protecting the Citarum riverbanks in Atirompe Village, Majalaya District. Using standardized unit price, the total price for the protection is 1,8 billion rupiahs.

Sedimentary texture of crevasse splays formed by present-day and palaeofloods against the background of floodplain geomorphology and lithofacies exposed in channel cut banks (in the Vistula River valley between Warsaw and Płock, Poland)

Abstract On the floodplain of a sandy, braided river in the Central European Lowland, we studied the sedimentary texture of two crevasse splays, which were: (1) formed due to a levee breach in the 2010 flood, and widely documented by hydrological, bathymetric and LIDAR data, (2) developed under natural conditions when the channel was not embanked by artificial levees (dikes). We compare the sedimentological results with a geomorphological map, a model of the floodplain geomorphology showing different facies of fluvial deposition derived from a meandering river, and deposits in cut banks of the river channel. The statistical parameters of the grain size composition and geomorphic features of the splay, shaped by overbank flow through the broken embankment, are similar to the natural landform. Most of the cut banks (60% of alluvial deposits were mapped there) consist of lithofacies representing proximal floodplain; 30% were distal floodplain (muds), and 10% channel (coarse sand with gravel, pebbles and cobbles). We speculate about the palaeogeography of the Lower Vistula, and the origin of muds and coarse deposits in the banks of the channel. We link these unusual sediments with avulsion, deposition in side arms during ice-jam conditions, and dredging of the channel bottom by suction excavator, which reached the fluvioglacial, suballuvial layer on the bedrock protrusion.

Fluvial geomorphic factors affecting liquefaction-induced lateral spreading

Liquefaction-induced lateral displacements represent a major geohazard in earthquake-prone regions, yet the uncertainty associated with their prediction remains notoriously high. Documented observations after recent earthquakes provide evidence that depositional environment-specific geologic conditions play a crucial role in liquefaction susceptibility, and in the severity and spatial extent of liquefaction-induced ground deformations. However, this evidence is largely qualitative in nature, which limits the potential to incorporate the effects of depositional processes and environments in the next generation of lateral spreading predictive models. This study provides a framework to quantitatively assess the relationship between depositional environment-specific geologic factors and lateral spreading by means of simple fluvial geomorphic facies models, geotechnical engineering data (e.g. Cone Penetration Test data), and geospatial analytics. Three hypotheses are introduced and tested using lateral spreading ground deformations observed following the 2011 Christchurch earthquake along the Avon and Heathcote rivers in New Zealand. The results from this study indicate that the presence of an active (i.e. with active sediment deposition) compared to inactive (e.g. abandoned) channels is the most important fluvial geomorphologic variable out of the three tested. The other two are associated with the location relative to the meander bend position, including location within the point bar (inside) or the cut bank (outside), and upstream versus downstream within a given point bar. Findings from this study show that more lateral spreading occurs within point bars, and upstream (within a given point bar) in simple meander bends. However, the presence of geomorphic complexities (e.g. cut banks connected to an incised channel or tributary and/or channel confinement) can challenge the unbiased quantification of the contribution of a single geomorphic variable to the observed lateral displacements. These findings can be applied to other fluvial environments outside of New Zealand, and the proposed framework can be implemented for other non-fluvial depositional settings.

Submarine groundwater discharge interacts with creek geomorphology to affect eastern oyster Crassostrea virginica growth rates in a coastal Georgia creek.

Eastern oysters, Crassostrea virginica, are commercially important coastal species that provide many ecosystem services for coastal communities. Unfortunately, 85% of oyster reefs have been lost globally, prompting investments in restoration efforts to rebuild populations. Managers often consider several well-studied environmental and water quality parameters when making restoration site decisions. However, recent research suggests that submarine groundwater discharge (SGD) may play a role in driving the distribution of oysters in some estuaries. Specifically, SGD may result in localized areas of low dissolved oxygen and low pH that could inhibit oyster recruitment and survival. However, SGD may interact with other potential oyster stressors, including creek geomorphology. On point bars, sediment accumulation could alter growth rates of oysters and physiology, and it is possible that the two factors, SGD and creek geomorphology, could interact to impact oyster growth. We conducted a field experiment to examine the effects of SGD and creek geomorphology on oyster growth rates in a marsh-lined tidal creek in Georgia, USA. High and low SGD sites were paired within point bars and cut banks. Oysters were deployed in cages for 72 days and growth rates were determined. We found a significant interaction between SGD and creek geomorphology on oyster growth rates. Oysters grew at significantly faster rates at locations on accretionary point bars regardless of SGD flux, whereas, on erosional cut banks, high SGD flux significantly reduced oyster growth rate relative to low SGD flux. It appears that SGD may negatively influence oyster growth at specific creek locations, likely due to the presence of other stressors. Therefore, it is important to consider potential interacting and confounding stressors when managing oyster populations. As SGD is still a relatively understudied potential stressor for oysters, it is critical to continue to examine how groundwater might influence oysters in other locations and in combination with other stressors. Regardless, this study provides further evidence that SGD should be considered in future management efforts.

Flood Scenario of Tigris River in Baghdad City

Flooding hazard is an important and dangerous natural phenomenon that leads to significant material losses. It should be studied and scenario to prevent significant losses. The studies should consider the impact of many factors such as human, infrastructure, economic,..etc. The main objective of the research is the risk management procedure. The study was conducted in Baghdad, Iraq. The materials for completing this research were prepared by gathering a satellite image and Digital Elevation Model (DEM) via the USGS website, then processed, analyzed, and converted into a different flood region concerning the probability of rising water levels where the normal height of Baghdad city is 28m over sea level. This scenario defines 3m, 4m, and 5m heights over the Tigris river cliff, which are the possible heights at which the water level may rise above the normal height. The range of the elevations becomes either 31m, 32m, or 33m over sea level. Many software’s were conducted in this research, such as MatLab, ArcGIS, and ENVI.

Understanding movement and habitat‐use to guide reintroductions and habitat rehabilitation for a nonmigratory freshwater fish

Outcomes from restoration and reintroduction programs can be enhanced by understanding the habitat use of animals, and how likely they are to move and why? River blackfish are native to southeastern Australia where their range and abundance have declined. We reintroduced 27 river blackfish into two sites, one where rehabilitation had been undertaken (with more vegetation, instream woody habitat, and undercut banks) and an unmanipulated control site. We monitored fish for 9 months after release to assess site occupancy, habitat use, and drivers of movement. We modeled the likelihood of fish remaining at either site, their habitat use, and predictors of movement (site type, habitat, time, and river discharge). While more fish remained at the treatment site, this difference was not statistically significant. Future trials incorporating increased numbers of fish and replicate treatment and control release sites would allow a more detailed test of whether fish are more likely to remain at restored sites. Fish spent more time in deeper areas with more riparian vegetation. Habitat, flow, and time since release were significant predictors of fish movement, with fish more likely to move from release sites with less suitable habitat, during rainfall events, and during the initial stages of our study. Our results illustrate that blackfish are a suitable candidate for translocations, retaining their largely sedentary behavior and should be easily measurable if restoration has provided suitable habitat and their presence is an indicator of success. Our work is also a useful case study for translocation of other nonmigratory fish worldwide.

Benthic metabolism and nutrient uptake vary with geomorphology and season in a lowland river

Meandering rivers are characterized by geomorphic units like cut banks, point bars, and thalwegs. These units arise from interactions between hydrological and geomorphological forces. However, the individual contributions of geomorphic units to whole-river metabolism or nutrient processing are unclear because these quantifications are often done at larger spatial scales. We used closed recirculating chambers to measure benthic gross primary production (GPP), respiration (R), N uptake or release, and P uptake or release at bimonthly intervals over 1 y at different geomorphic units in the Mulde River, Germany. We compared GPP, R, and nutrient processing among a cut bank, a point bar, and the thalweg at a natural meander. We also compared the cut bank of this natural meander with a cut bank fixed by riprap at a human-altered meander. In the natural meander, GPP, R, and nutrient processing rates were higher at the point bar than the cut bank or thalweg. These differences are likely related to larger sediment grain sizes that provide a more stable substrate for microbial communities. A strong interaction between geomorphic units and time for GPP and NH4+ fluxes suggested that differences in nutrient processing rates among geomorphic units were restricted to specific times during the year. Specifically, we found that the nutrient processing rates differed among geomorphic units during the summer, but not winter. Furthermore, in June and August 2017, R was 2 to 3× lower at the cut bank stabilized by riprap than at the natural cut bank. Our results demonstrate that rivers are composed of functionally distinct geomorphic units susceptible to human-induced hydromorphological degradation. However, strong interactions between space and time and large within-geomorphic unit variability propose that local drivers influence ecosystem function, suggesting that we need additional research to resolve these drivers at the scales of geomorphic units.

CONSEQUENCES OF MASSIVE RIVER BANK EROSION TO THE LOCAL SOCIETY AT PASIR PARIT, KELANTAN

The population living near the river basin is at risk of river bank erosion. As a consequence of hydraulics and hydrological processes, as well as floods and development activities along the river, the morphology is changing. Many ecological characteristics, including as flora and fauna, human life, basin structure, and so on, may be lost as a consequence of river bank erosion. The objectives of this research are to (1) identify the impact of soil texture on river bank erosion; (2) determine the consequences of river bank erosion on the local community; and (3) propose river bank erosion mitigation strategies for the study region. We use both quantitative and qualitative approaches to analyse data in this study. An observational technique, a questionnaire survey, and a personal interview were utilised to collect data. To support our findings, we acquired secondary data from government entities (Drainage and Irrigation Department). The river bank erosion in this case study affected 17 dwellings, totaling 103 people, and two homes were consumed by the river. The impacted area of river bank erosion at the site, according to the research conclusions based on aerial photography and departmental statistical data, is roughly 120 metres in a period of 6 months. The volume of sediment lost due to bank erosion was estimated to be 360,000 cubic metres, or 1.4 hectares. As a consequence of the massive river bank erosion, the victims had endured loss and worry. The following technique for preventing river bank erosion is proposed: build a concrete river cliff or gabion as soon as possible, and change the low weir so that flowing and flood water are contained in the river's main channel.

Analisis Kinerja Alat Berat Pada Proyek Normalisasi dan Perkuatan Tebing Sungai

The purpose of this study was to analyze the performance of heavy equipment and the duration of time required to complete the Windo River Cliff Normalization and Reinforcement Project, Pamandati Village, Laeya District, South Konawe Regency. The results showed that the excavator's performance in excavation work (mechanical) was 38.68 m3/hour, dump truck 2.99 m3/hour. As for the embankment work imported from outside, the performance of the excavator is 98.53 m3/hour and the dump truck is 3.05 m3/hour. Where the duration of time required to complete the excavation work (mechanical) with an excavator is 12 days and for embankment work imported from outside is 2 days..

Organic matter characteristics of a rapidly eroding permafrost cliff in NE Siberia (Lena Delta, Laptev Sea region)

Abstract. Organic carbon (OC) stored in Arctic permafrost represents one of Earth's largest and most vulnerable terrestrial carbon pools. Amplified climate warming across the Arctic results in widespread permafrost thaw. Permafrost deposits exposed at river cliffs and coasts are particularly susceptible to thawing processes. Accelerating erosion of terrestrial permafrost along shorelines leads to increased transfer of organic matter (OM) to nearshore waters. However, the amount of terrestrial permafrost carbon and nitrogen as well as the OM quality in these deposits is still poorly quantified. We define the OM quality as the intrinsic potential for further transformation, decomposition and mineralisation. Here, we characterise the sources and the quality of OM supplied to the Lena River at a rapidly eroding permafrost river shoreline cliff in the eastern part of the delta (Sobo-Sise Island). Our multi-proxy approach captures bulk elemental, molecular geochemical and carbon isotopic analyses of Late Pleistocene Yedoma permafrost and Holocene cover deposits, discontinuously spanning the last ∼52 kyr. We showed that the ancient permafrost exposed in the Sobo-Sise cliff has a high organic carbon content (mean of about 5 wt %). The oldest sediments stem from Marine Isotope Stage (MIS) 3 interstadial deposits (dated to 52 to 28 cal ka BP) and are overlaid by last glacial MIS 2 (dated to 28 to 15 cal ka BP) and Holocene MIS 1 (dated to 7–0 cal ka BP) deposits. The relatively high average chain length (ACL) index of n-alkanes along the cliff profile indicates a predominant contribution of vascular plants to the OM composition. The elevated ratio of iso- and anteiso-branched fatty acids (FAs) relative to mid- and long-chain (C ≥ 20) n-FAs in the interstadial MIS 3 and the interglacial MIS 1 deposits suggests stronger microbial activity and consequently higher input of bacterial biomass during these climatically warmer periods. The overall high carbon preference index (CPI) and higher plant fatty acid (HPFA) values as well as high C/N ratios point to a good quality of the preserved OM and thus to a high potential of the OM for decomposition upon thaw. A decrease in HPFA values downwards along the profile probably indicates stronger OM decomposition in the oldest (MIS 3) deposits of the cliff. The characterisation of OM from eroding permafrost leads to a better assessment of the greenhouse gas potential of the OC released into river and nearshore waters in the future.

Changes of Divergence and Confluence Relationship Between Dongting Lake and the Yangtze River After the Operation of the Three Gorges Project and Its Impact on the Waterway Depth

Human activities and climate change have profoundly changed the hydrological and geomorphological evolutionary processes and trends of rivers and lakes, which, in turn, has affected the utilization of their waterway depth. This study chose the Dongting Lake–Jingjiang confluence of the Changjiang River (Yangtze Rvier), since the operation of the Three Gorges Project, the split ratio of water and the sediment distribution of the three outlets of Dongting Lake—that is, Songzikou, Taipigkou, and Ouchikou—have continued to decrease. Along with the decreasing flow of Dongting Lake, the relative increase in the runoff of the Jingjiang reach and the increase in riverbed erosion intensity have increased the relative height difference between Jingjiang and Dongting Lake, intensifying the reduction of the split ratio of water and the sediment distribution of the three outlets. The riverbed erosion of the Jingjiang reach has created a promising foundation for an increase in the waterway dimensions. However, the length of the reach not meeting the requirements of 4.5× 200 m (water depth × width) is 18.4 km, of which the length in the river-lake confluence is 12.6 km, accounting for 68.35% of the total length of obstructed navigation. Furthermore, at the reach (Zhicheng–Dabujie reach) affected by the first outlet (Songzikou), a 4.5-m flume has been formed, but its width is less than 200 m. Moreover, the “steep slope and rapid current” phenomenon is clear, and it affects the safety of ships. At the reach (Taipingkou reach) affected by the second outlet, the shrinkage of the bottomland, and the intersecting braided river channels make the low-flow routes unstable, the water depth being less than 4.5 m. At the reach (Tianxingzhou–Ouchikou reach) affected by the third outlet, the shoreline of the reach has collapsed and retreated significantly. Additionally, beach erosion and the downstream movement of cut banks have caused the downstream waterway width at the reach to be reduced to less than 200 m or formed shoals with a water depth of less than 4.5 m. Owing to the jacking effect of the lake’s outflow backwater, the flow rate of the reach (Xiongjiazhou–Chenglingji reach) affected by the confluence of Dongting Lake decreased, creating a shoal with a water depth of less than 4.5 m in the navigation waterway. The results of this study have guiding significance for understanding the changes of channel conditions and the improvement of channel scale in the intersection area of rivers and lakes.

The Lower Rhine (Germany) in Late Antiquity: a time of dissolving structures

Abstract From the middle of the 1st century AD, the Lower Rhine was part of the frontier of the Roman Empire (Limes). However, this Limes was not an impermeable line, but rather an open corridor that served as march area and as a trade and supply route for the adjacent military and civilian settlements as well as the hinterland. This required access to the river and permanent harbours. When planning military camps and towns along the Rhine, the existing topography and the challenge of a dynamic riverine landscape had to be taken into account. The prefered location for forts and towns were the raised edges of the Lower Terraces close to the undercut bank of a meander. For many years, research assumed that the river bend adjacent to a Roman site had to be an oxbow lake. The main argument being that only an oxbow situation would have protected the Roman sites against strong currents and the risk of demolition of land and settlements by the main stream (abandoned channel hypothesis). A re-evaluation of the extensive archaeological, sedimentological and palynological archive and published data from the Rhine plain, as well as of supplementary data from new boreholes, lead to a considerable increase in the previously incomplete knowledge of the fluvial history, especially regarding the timing of palaeomeander infilling. It showed that most of the meanders and river bends of the Rhine with Roman settlements on their banks not silted up before Late Antiquity (from the end of the 3rd century AD on). Before that those meanders were part of the main stream. The advantage of steep undercut banks was that a quay could be built on a location that ensured mooring all year round, even at low water level. However, it was necessary that stabilising bank protections were present in order to avoid shifting the course of the river with subsequent destruction of the infrastructure. Such an antique bank protection construction (a so called “Packwerk”) could be recognised in front of the Colonia Ulpia Traiana (CUT, Xanten). With this knowledge in mind, other excavated structures on the banks of palaeomeanders, previously mostly interpreted as Roman harbour remains, could be interpreted as bank protections. At Wesel near the strategically important mouth of the Lippe, the archaeological, sedimentological and palynological data showed that a meander that had silted up in Prehistoric times (Bronze Age) had been reactivated in Roman times and silted up again in Late Antiquity. A man-made diversion (perhaps by building a groyne) of the main stream could have been responsible for this. With the beginning of the Late Antiquity crisis of the Roman Empire at the end of the 3rd century, it presumably became increasingly difficult to maintain these water works. This enabled the river to regain its morphodynamics, by cutting of the meanders that were active during Roman times. We hypothesise that this increase in fluvial activities of the Lower Rhine from the end of the 3rd century onwards is due to an anthropogenic trigger: the collapse of the Roman Empire.

Analisis Normalisasi Sungai Baubau

River normalization and cliff strengthening are efforts to controlflooding that occurs in rivers such as the Baubau River. In 2012, therewere floods in 20 spots due to the overflowing of the Baubau Riverso that a flood prevention plan is needed.This study aims to determine the method of flood management inthe Baubau River, with variable of cross-sectional areas (1) rivertopographical data, (2) land use and soil bearing capacity (1) soilshear force, (2) rolling force and the river length studied is about 1.3Km.The results of the analysis show that the flood discharge of BaubauRiver is (1) 10.69m3/s, 2 year return period, (2) 15,39 m3/s 5 yearreturn period, (3) 18,50 m3/s 10 year return period (4) 22,43 m3/sfor 25 years, (5) 25,35 m3/s for 50 years, (6) 28,25 m3/s for 100years, so the handling method used in the Baubau River is tonormalize the river with a trapezoidal model (b = 3,69 m, B = 10,40m, h = 3,20 m, H = 4,46 m, and W = 1,26 m for the 25 year returnperiod) and the strengthening of cliffs on the right and left of thetalud model ( h = 5.7 m, bottom width 3.5 m, and top width 0.5 m).

KAJIAN KERUSAKAN DAN KERUNTUHAN TUBUH BENDUNG AKIBAT PENGARUH BANJIR (STUDI KASUS : BENDUNG CIPAMINGKIS KAB. BOGOR)

Land use in the vicinity of Cipamingkis Sub-watershed is currently very intensive, so that damage to land which is feared has an impact on the level of fertility and carrying capacity of the land, resulting in the danger of flooding, erosion and landslides in the rainy season, as well as a decrease in water discharge and lack of groundwater in the season dry. The impact of these conditions Cipamingkis Weir in Sukasirna Village, Jonggol District on April 20, 2017 there was a breakdown of the lighthouse and the body of the weir which was built since 1982, the dam irrigated 4579 Ha of rice fields, unable to irrigate and in the lower reaches of the dam a lot of damage, including: eroded riverbanks, damaged river cliffs, and part of the land cracked and landslides.Seeing the condition needs to be made a research on Cipamingkis Dam Damage Study. This handling is urgently needed to reduce and reduce the consequences caused in the process of activities that cause erosion and flooding.

Groundwater–surface water interactions in a river estuary and the importance of geomorphology: Insights from hydraulic, thermal and geophysical observations

AbstractThis study presents the groundwater flow and salinity dynamics along a river estuary, the Werribee River in Victoria, Australia, at local and regional scales. Along a single reach, salinity across a transverse section of the channel (~80 m long) with a point bar was monitored using time‐lapse electrical resistivity (ER) through a tidal cycle. Groundwater fluxes were concurrently estimated by monitoring groundwater levels and temperature profiles. Regional porewater salinity distribution was mapped using 6‐km long longitudinal ER surveys during summer and winter. The time‐lapse ER across the channel revealed a static electrically resistive zone on the side of the channel with a pronounced cut bank. Upward groundwater flux and steep vertical temperature gradients with colder temperatures deeper within the sediment suggested a stable zone of fresh groundwater discharge along this cut bank area. Generally, less resistive zones were observed at the shallow portion of the inner meander bank and at the channel center. Subsurface temperatures close to surface water values, vertical head gradients indicating both upward and downward groundwater flux, and higher porewater salinity closer to that of estuary water suggest strong hyporheic circulation in these zones. The longitudinal surveys revealed higher ER values along deep and sinuous segments and low ER values in shallow and straighter reaches in both summer and winter; these patterns are consistent with the local channel‐scale observations. This study highlights the interacting effects of channel morphology, broad groundwater–surface water interaction, and hyporheic exchange on porewater salinity dynamics underneath and adjacent to a river estuary.

Middle to late Holocene alluvial history of the northeast monsoon dominated coastal tropical rivers of south India

The region around the coastal Chennai area, India, is drained by three major rivers that rise from the remnants of the Eastern Ghats and receive dominantly the northeast rains. These rivers meander short distances, deposit sediments into the Bay of Bengal and preserve signatures of past phases of sedimentation and incision. In this study, detailed mapping using satellite imageries and extensive field work, logging of the river cliff bank sections was supported by sediment texture and structure and optically stimulated luminescence (OSL) dates. The main objective of this study was to infer the major periods of aggradation and incision in coastal drainage basins receiving dominantly the northeast rains. Integration of all the earlier available dated alluvial sequences (14C ages) and the present study OSL dates reveal that a major period of sedimentation occurred during the early Holocene (9 to 8.3 ka), mid Holocene (7.6–5.5 ka) and late Holocene to recent (2.4 and 1.6 ka, 0.9–0.6 ka and around 0.2 ka) periods. The Koratallaiyar river has preserved older middle Holocene terraces. Younger ages of the south easterly and east flowing rivers such as the Palar and the Coovum signify that they have incised and eroded to the present riverbed levels by catastrophic floods during the late Holocene period. This has resulted in an imbalance between sediment supply and sediment transporting power thus laterally stacking sediments rather than vertically.