8,614 research outputs found

    An Integrated Coastal Sediment Management Plan: The Example of the Tuscany Region (Italy)

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    This paper presents the results of a study carried out to support the Region of Tuscany Coastal Sediment Management Plan, with the main aim of establishing the sediment budget considering the time span from 1981-1985 to 2005 for the 56 coastal sectors into which the 215 km-long continental sandy coast of Tuscany (Italy) was divided. The sand stability (according to a stability index) and colour compatibility (according to the CIEL*a*b* colour space with an acceptability range conforming to national guidelines) were determined in order to assess the possibility of using the available sediment in accreting sectors to nourish the beach in eroding areas. Only in two cases-i.e., the updrift of a harbour (at Viareggio) and in a convergence zone (at Marina di Pietrasanta)-are the volumes of sufficient magnitude to support a large nourishment project; however, the mean sand size is too small to guarantee efficient nourishment, even with medium-term stability. In contrast, the colour difference, in most of the cases, was shown to be acceptable. Other small sediment stocks, suitable for colour but not for grain size, can be used for periodic ephemeral nourishment works to support seasonal tourist activities. The limited resources available make it necessary to adopt a plan for their optimal use from a regional perspective. This kind of study is of great interest for the proposal of sound management actions to counteract the increasing erosion processes linked to climate change phenomena and human effects on rivers and coastal systems

    A novel approach for the assessment of morphological evolution based on observed water levels in tide-dominated estuaries

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    Assessing the impacts of both natural (e.g., tidal forcing from the ocean) and human-induced changes (e.g., dredging for navigation, land reclamation) on estuarine morphology is particularly important for the protection and management of the estuarine environment. In this study, a novel analytical approach is proposed for the assessment of estuarine morphological evolution in terms of tidally averaged depth on the basis of the observed water levels along the estuary. The key lies in deriving a relationship between wave celerity and tidal damping or amplification. For given observed water levels at two gauging stations, it is possible to have a first estimation of both wave celerity (distance divided by tidal travelling time) and tidal damping or amplification rate (tidal range difference divided by distance), which can then be used to predict the morphological changes via an inverse analytical model for tidal hydrodynamics. The proposed method is applied to the Lingdingyang Bay of the Pearl River Estuary, located on the southern coast of China, to analyse the historical development of the tidal hydrodynamics and morphological evolution. The analytical results show surprisingly good correspondence with observed water depth and volume in this system. The merit of the proposed method is that it provides a simple approach for understanding the decadal evolution of the estuarine morphology through the use of observed water levels, which are usually available and can be easily measured.National Key R&D of China (Grant No. 2016YFC0402601), National Natural Science Foundation of China (Grant No. 51979296, 51709287, 41706088, 41476073), Fundamental Research Funds for the Central Universities (No.18lgpy29) and from the Water Resource Science and Technology Innovation Program of Guangdong Province (Grant No. 2016-20, 2016-21). The work of the second author was supported by FCT research contracts IF/00661/2014/CP1234.info:eu-repo/semantics/submittedVersio

    Modeling of extreme freshwater outflow from the north-eastern Japanese river basins to western Pacific Ocean

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    This study demonstrates the importance of accurate extreme discharge input in hydrological and oceanographic combined modeling by introducing two extreme typhoon events. We investigated the effects of extreme freshwater outflow events from river mouths on sea surface salinity distribution (SSS) in the coastal zone of the north-eastern Japan. Previous studies have used observed discharge at the river mouth, as well as seasonally averaged inter-annual, annual, monthly or daily simulated data. Here, we reproduced the hourly peak discharge during two typhoon events for a targeted set of nine rivers and compared their impact on SSS in the coastal zone based on observed, climatological and simulated freshwater outflows in conjunction with verification of the results using satellite remote-sensing data. We created a set of hourly simulated freshwater outflow data from nine first-class Japanese river basins flowing to the western Pacific Ocean for the two targeted typhoon events (Chataan and Roke) and used it with the integrated hydrological (CDRMV3.1.1) and oceanographic (JCOPE-T) model, to compare the case using climatological mean monthly discharges as freshwater input from rivers with the case using our hydrological model simulated discharges. By using the CDRMV model optimized with the SCE-UA method, we successfully reproduced hindcasts for peak discharges of extreme typhoon events at the river mouths and could consider multiple river basin locations. Modeled SSS results were verified by comparison with Chlorophyll-a distribution, observed by satellite remote sensing. The projection of SSS in the coastal zone became more realistic than without including extreme freshwater outflow. These results suggest that our hydrological models with optimized model parameters calibrated to the Typhoon Roke and Chataan cases can be successfully used to predict runoff values from other extreme precipitation events with similar physical characteristics. Proper simulation of extreme typhoon events provides more realistic coastal SSS and may allow a different scenario analysis with various precipitation inputs for developing a nowcasting analysis in the future

    An Attempt to Characterize the "3S" (Sea, Sun, and Sand) Parameters: Application to the Galapagos Islands and Continental Ecuadorian Beaches

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    Sea, Sun, and Sand (3S) are relevant and determining elements for choosing a tourist destination in Ecuador, a country with about 1200 km of coast along the Pacific Ocean. This study analyzed the market potential of the 3S in 64 beaches, 10 located in the Galapagos and 54 in the continental zone (of Ecuador). The methodology used was exploratory and bibliographical, complemented by a descriptive analysis. The color of the water was assessed by direct observation, sand samples were taken to a laboratory for color analysis, and information on the hours of light was obtained from international archive data. The data obtained were compared with other world famous 3S tourism destinations. The Galapagos had the best results, with attractive white sand beaches, sea blue water color, and an elevated sunshine time; meanwhile, the continental zone presented poor beaches with dark sand and unattractive water color. To strengthen 3S tourism, managers should work on the enhancement of complementary aspects such as culture, gastronomy, and architecture, promoting the creation of new coastal tourist routes and destinations

    2008 Nebraska Fishing Guide

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    Contents: Archery/Surface Spearfishing . . . . . . . . . . . 17 ATVs and Snowmobiles/Ice-Fishing . . . . . . . 19 Bag & Possession Limits . . . . . . . . . . . . . . . . 6 Baitfish Listing . . . . . . . . . . . . . . . . . . . . . . . 15 Bait Regulations . . . . . . . . . . . . . . . . . . . . . . 13 Border Waters . . . . . . . . . . . . . . . . . . . . . . . 19 Bullfrogs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Cast Nets . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Commercial Fish Listing . . . . . . . . . . . . . . . . 14 Conservation Officers . . . . . . . . . . . . . . . . . 55 Fish Kill Reports . . . . . . . . . . . . . . . . . . . . . . . 4 Game and Parks Commission Offices . . . . . . 2 Hook & Line Seasons and Regulations . . . . 12 Know What You Caught . . . . . . . . . . . . . . 8-10 Master Angler Application . . . . . . . . . . . . . . 27 Mussels (Clams) . . . . . . . . . . . . . . . . . . . . . 19 Nongame Fish Listing . . . . . . . . . . . . . . . . . 15 Paddlefish Application Form . . . . . . . . . . . . 22 Paddlefish - Archery (Missouri River) . . . . . 21 Paddlefish Harvest Tags . . . . . . . . . . . . . . . 23 Paddlefish and Snagging of Nongame Fish 20 Panfish Listing . . . . . . . . . . . . . . . . . . . . . . . 14 Permit Fees and Requirements . . . . . . . . . . . 3Private Waters . . . . . . . . . . . . . . . . . . . . . . . 24 Public Fishing Areas Panhandle (District I) . . . . . . . . . . . . . . . . . 28 North-central (District II) . . . . . . . . . . . . . . 31 Northeast (District III) . . . . . . . . . . . . . . . . . 34 Southwest (District IV) . . . . . . . . . . . . . . . . 38 South-central (District VI) . . . . . . . . . . . . . . 40 Southeast (District V) . . . . . . . . . . . . . . . . . 46 Regulation Changes For 2008 . . . . . . . . . . . .4 Snagging . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Snapping Turtles . . . . . . . . . . . . . . . . . . . . . 19 Sport Fish Listing . . . . . . . . . . . . . . . . . . . . . 14 State Record and Master Angler Rules . 25-27 Threatened and Endangered Species . . . . . 15 Tournaments/Contests/Derbies . . . . . . . . . . 24 Underwater Spearfishing . . . . . . . . . . . . . . . 18 Unlawful Acts . . . . . . . . . . . . . . . . . . . . . . . . .

    Distribution of freshwater fish in the south-western corner of Australia

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    This study investigates the distribution of freshwater fishes in the Busselton to Walpole Region. A total of 311 sites in 19 major catchments along the south-west coast from Capel to Walpole, were sampled using a variety of methods. New data was collated with that from previous studies to generate 15 species distribution maps. Habitat and life history notes and recommendations for conservation are made for each species. Changes in fish distribution are also commented upon. This study contributes to series of documents published for the purposes of water allocation planning in the Busselton to Walpole Region

    Vertically layered flow structure at confluence of a reservoir and tributary carrying high sediment loads

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    Enhanced understanding of flow structure at a river confluence is essential for predictions of sediment transport and morphological evolution. To date, however, the confluent flow structure of a reservoir and tributary carrying high sediment loads has remained poorly understood, and may be vertically layered sharply, featuring subaqueous sediment-laden flow, i.e., turbidity currents underneath subaerial clear water. Here a recently established 2D double layer-averaged model, able to resolve the formation, propagation, and recession of turbidity currents, is used to investigate a series of idealized laboratory-scale cases and a prototype case study of the Guxian Reservoir on the Yellow River, China. Four primary patterns of the stable, vertically layered flow structure at a reservoir-tributary confluence are identified: 1) single layers of sediment-laden inflow in both the main channel and tributary, sustained by sufficient vertical mixing; 2) a double layer in the main channel and a single layer of sediment-laden inflow in the tributary, when the sediment-laden flow in the tributary suffices to block intrusion of flow in the main channel; 3) a single layer of sediment-laden inflow in the main channel and a double layer in the tributary, induced by the intrusion of sediment-laden flow from the main channel into clear-water flow with small discharge in the tributary; and 4) double layers in both the main channel and tributary, which may be further divided into three subpatterns, as turbidity current exists in both the main channel and tributary, or in the main channel (tributary) intruding into the tributary (main channel). In response to unsteady discharge and sediment inputs from upstream, the vertically layered flow structure evolves in time, and may fall into one of the patterns identified above. Although bed deformation in the long term may modify the confluent flow, the vertically layered flow pattern remains so far as the present cases are concerned. The findings have implications for sediment transport and morphological evolution at a reservoir–tributary confluence, for which further studies are suggested to inform the optimization of reservoir operation schemes to mitigate capacity loss caused by sedimentation

    Balancing Sediment Connectivity and Energy Production via Optimized Reservoir Sediment Management Strategies

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    Sediment connectivity plays a fundamental role in sustaining ecosystem goods and services in fluvial systems, including hydropower production. Dams alter the natural processes of sediment transport by trapping sediment and reshaping downstream hydrology and geomorphology. Due to these processes' interconnected nature, dams' impacts extend in time and space beyond the dam site to the entire river system. System-scale approaches to reduce dam impacts commonly only consider dam siting, overlooking the potential of sediment management strategies integrated into the dam operations to offer more flexible solutions for mitigation. Herein, we contribute a sediment routing model (D-CASCADE) to assess the impacts of reservoirs and their management strategies on river sediment connectivity. D-CASCADE is applied to the 3S river system, a tributary of the Mekong River, a hotspot of potential dams in the Lower Mekong. We analyze three dam development portfolios. The effect of reservoir management is examined by assessing daily sediment delivery with specific dam release strategies. Model results predict sediment yield to the Mekong to reduce by 31%-60%. Finally, we explore trade-offs between hydropower generation and sediment connectivity across cascades of multiple reservoirs. Results show that repeated flushing operations during the early wet season could significantly increase sediment delivery with minimal (max 6%) hydropower losses. While poor trade-offs between sediment and hydropower have been locked-in in the Mekong, our results highlight the potential of including sediment connectivity models in multi-objective decision-making frameworks to devise integrated water and sediment management strategies that mitigate connectivity disruptions while minimizing losses in other sectors
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