Shoreline Erosion and Restabilization in the Southern Indian Lake Reservoir

1984 ◽  
Vol 41 (4) ◽  
pp. 558-566 ◽  
Author(s):  
R. W. Newbury ◽  
G. K. McCullough
Keyword(s):  
Water Level ◽  
Wave Energy ◽  
Wave Action ◽  
Shoreline Erosion ◽  
Energy Component ◽  
Minimum Period ◽  
M Wave ◽  
Fine Grained ◽  
Erosion Rates

Prior to a 3-m impoundment in 1976, bedrock comprised 76% of the shoreline of Southern Indian Lake in northern Manitoba. This was reduced to only 14% of the shoreline as the water level rose above the wave-washed zone and flooded into the predominantly fine-grained, frozen overburden materials. Twenty monitoring sites were surveyed annually to determine rates of permafrost melting and solifluction and shoreline erosion. The sequence of shoreline erosion in permafrost materials was found to be cyclic, consisting of melting and undercutting of the backshore zone, massive faulting of the overhanging shoreline, and removal of the melting and fractured debris. Rates of shoreline erosion varied widely, depending on the exposure of the site to wave action and the composition of the backshore materials. At sites in fine-grained frozen silts and clays, representative of over three quarters of the postimpoundment shoreline, rates of retreat of up to 12 m∙yr−1 were observed. The total volume of shoreline materials removed varied from less than 1 to over 23 m3∙m shoreline length−1∙yr−1. Clearing of the forested backshore prior to flooding did not affect the erosion rates. The index of erosion based on the hindcast wave energy component perpendicular to the shoreline was 0.00035 m3∙t-m wave energy−1 (0.036 m3∙MJ−1). The minimum period of restabilization of the shoreline based on the volume of backshore materials that must be eroded before bedrock conditions are reestablished was estimated to be 35 yr for three quarters of the shoreline surrounding the lake.

scholarly journals BLUFF RETREAT INDUCED BY WAVE ACTION ON A TROPICAL BEACH, IN ESPÍRITO SANTO, BRAZIL

2018 ◽  
Vol 36 (4) ◽  
pp. 1
Author(s):  
Branco Mateus Murata Eguchi ◽  
Jacqueline Albino
Keyword(s):  
Energy Distribution ◽  
Wave Energy ◽  
Urban Expansion ◽  
High Energy ◽  
Temporal Variations ◽  
Wave Exposure ◽  
Wave Action ◽  
Short Term ◽  
Erosion Rates ◽  
Bluff Erosion

ABSTRACT. Interest in understanding sea bluff erosion along the coasts around the world has grown in recent years, especially when in proximity to urban expansion. To prevent economic, social and environmental losses, it is necessary to understand the factors behind the sea bluff erosion. This study analyzed temporal and spatial changes in wave exposure over 60 years (1948-2008) and the corresponding impacts of these variations on three sea bluffs with similar lithology over 55 years (1953-2008). Erosion distances and annual erosion rates were obtained from aerial and satellite images for the time intervals 1953-1970, 1970-1995 and 1995-2008. Analysis of bluff retreat and wave exposure compared annual wave behavior, extreme wave occurrences and modeled spatial and temporal variations in wave energy to yearly retreat rates obtained from imagery analysis and assessed for each of the three intervals. For the three bluffs, the total erosion distance decreased northward – 51, 43 and 18 m, resulting in recession rates of 0.8, 0.69 and 0.43 m/year, respectively. Overall, annual erosion rates appear to slow down during long periods (63 years) compared to the short-term (8-25 years). The shift in modeled wave energy distribution is mainly in accordance with the longshore variability of erosion rates. However, the relationship between bluff recession and wave energy shows that periods of high energy are not necessarily related to intense bluff recession. The erosion process induces debris deposition, which may be able to protect the bluff toe from wave action for a while. The bluffs in our study receded at different rates, despite proximity, in response to spatial and temporal differences in wave energy distribution. Based on results, we propose a bluff erosion cycle model for the studied area and infer current erosion vulnerability.Keywords: Short-term events, decadal mobility, wave exposition, bluff cycle model.RESUMO. Nas últimas décadas, questões relativas à erosão de falésias marinhas têm sido importantes ao longo das costas ao redor do mundo, especialmente devido à expansão urbana nessas áreas. Torna-se, portanto, necessário entender os fatores por trás do processo de erosão destas falésias, a fim de evitar perdas econômicas, sociais e ambientais. Este estudo analisou como o grau de exposição às ondas muda ao longo do tempo, no espaço entre 1948 e 2008, e também os impactos desta modificação sobre três falésias com mesma litologia, durante o intervalo de 1953-2008. Distâncias erodidas e taxas de erosão anual foram obtidas através da análise de imagens de satélite e aérea para os intervalos de tempo de 1953-1970, 1970-1995 e 1995-2008. A correlação entre o recuo das falésias e a ação das ondas foi baseada no comportamento das alturas significativas médias anuais, ocorrência de onda extremas e modelagem da variação espaço/temporal da energia de onda de 1953 a 2008. O recuo das três falésias estudadas apresenta um incremento no sentido norte-sul, variando de 51, 43 a 18 m, resultando em taxas erosivas anuais de 0,8; 0,69 e 0,43 m/ano, respectivamente. Em geral, taxas de erosão parecem menores durante longos períodos (63 anos) em comparação com taxas de curto prazo (8-25 anos). Além disso, a mudança na distribuição de energia de onda modelada se mostra de acordo com a variabilidade espaço/temporal das taxas de erosão. No entanto, os resultados mostram que fases de alta energia de ondas não estão necessariamente relacionadas com intenso recuo das falésias. Discute-se que processo de erosão induz a deposição de detritos na base da falésia, que podem ser capazes de proteger da ação de onda até que sejam transportados para o mar. Portanto, conclui-se que falésias homogêneas mostram ritmos diferentes de recessão que respondem a alterações espaciais e temporais em distribuição de energia de onda. Além disso, a partir do modelo esquemático do ciclo de erosão no pé de falésias proposto neste estudo, é possível inferir a atual vulnerabilidade de erosão das falésias estudadas com base nos resultados obtidos.Palavras-chave: Eventos a curto prazo, mobilidade decadal, exposição às ondas, modelo evolutivo de falésias.

scholarly journals Water level oscillations in Monterey Bay and Harbor

Ocean Science ◽  
2015 ◽  
Vol 11 (3) ◽  
pp. 439-453 ◽  
Author(s):  
J. Park ◽  
W. V. Sweet ◽  
R. Heitsenrether
Keyword(s):  
Water Level ◽  
Wave Energy ◽  
Normal Modes ◽  
Low Frequency ◽  
Water Levels ◽  
Level Data ◽  
Modal Amplitude ◽  
Primary Driver ◽  
Potential Mode ◽  
Offshore Wave

Abstract. Seiches are normal modes of water bodies responding to geophysical forcings with potential to significantly impact ecology and maritime operations. Analysis of high-frequency (1 Hz) water level data in Monterey, California, identifies harbor modes between 10 and 120 s that are attributed to specific geographic features. It is found that modal amplitude modulation arises from cross-modal interaction and that offshore wave energy is a primary driver of these modes. Synchronous coupling between modes is observed to significantly impact dynamic water levels. At lower frequencies with periods between 15 and 60 min, modes are independent of offshore wave energy, yet are continuously present. This is unexpected since seiches normally dissipate after cessation of the driving force, indicating an unknown forcing. Spectral and kinematic estimates of these low-frequency oscillations support the idea that a persistent anticyclonic mesoscale gyre adjacent to the bay is a potential mode driver, while discounting other sources.

scholarly journals On the coupling between unstable magnetospheric particle populations and resonant high <i>m</i> ULF wave signatures in the ionosphere

2005 ◽  
Vol 23 (2) ◽  
pp. 567-577 ◽  
Author(s):  
L. J. Baddeley ◽  
T. K. Yeoman ◽  
D. M. Wright ◽  
K. J. Trattner ◽  
B. J. Kellet
Keyword(s):  
Wave Energy ◽  
Low Frequency ◽  
Distribution Functions ◽  
Wave Number ◽  
Particle Interactions ◽  
Ion Distribution ◽  
M Wave ◽  
Ulf Wave ◽  
Energy Dissipated ◽  
Giant Pulsations

Abstract. Many theories state that Ultra Low Frequency (ULF) waves with a high azimuthal wave number (m) have their energy source in wave-particle interactions, yet this assumption has been rarely tested numerically and thus many questions still remain as to the waves' exact generation mechanism. For the first time, this paper investigates the cause and effect relationship between the driving magnetospheric particle populations and the ULF wave signatures as observed in the conjugate ionosphere by quantitatively examining the energy exchange that occurs. Firstly, a Monte Carlo method is used to demonstrate statistically that the particle populations observed during conjugate ionospheric high m wave events have more free energy available than populations extracted at random. Secondly, this paper quantifies the energy transferred on a case study basis, for two classes of high m waves, by examining magnetospheric Ion Distribution Functions, (IDFs) and directly comparing these with the calculated wave energy dissipated into the conjugate ionosphere. Estimates of the wave energy at the source and the sink are in excellent agreement, with both being of the order of 1010J for a typical high m wave. Ten times more energy (1011J) is transferred from the magnetospheric particle population and dissipated in the ionosphere when considering a subset of high m waves known as giant pulsations (Pgs). Previous work has demonstrated that 1010J is frequently available from non - Maxwellian IDFs at L=6, whereas 1011J is not. The combination of these studies thus provides an explanation for both the rarity of Pgs and the ubiquity of other high m waves in this region.

MODELING SPILLED OIL PARTITIONING IN NEARSHORE AND SURF ZONE AREAS

1985 ◽  
Vol 1985 (1) ◽  
pp. 379-383 ◽  
Author(s):  
Erich R. Gundlach ◽  
Timothy W. Kana ◽  
Paul D. Boehm
Keyword(s):  
Wave Energy ◽  
Surf Zone ◽  
High Energy ◽  
Sandy Beaches ◽  
Coarse Grained ◽  
Tidal Range ◽  
Incoming Wave ◽  
Fine Grained ◽  
Beach Sediments ◽  
Rocky Coasts

ABSTRACT The shoreline of a potential spill impact area can be divided into units, each with a specific geomorphology. As oil enters each unit, it will (to varying extents) evaporate, dissolve, interact with suspended particles and sink, biodegrade, photo-oxidize, be transported to the next unit, or strand on the shoreline. In the last case, oil will reenter the aquatic system after a given time and again be exposed to these same processes. For modeling purposes, the world's shorelines can be divided into sedimentary beaches and tectonic rocky coasts, varying in wave energy and tidal range. The size of beach sediments can range from very coarse grained (gravels) to very fine grained (silts and clays). Coarse-grained shorelines have higher incoming wave energy than fine-grained areas. Along all coasts, several partitioning components remain relatively constant for medium to light crude oils, e.g., evaporation (30 to 50 percent) and biodegradation/photo-oxidation (0 to 5 percent). Others may vary substantially. For instance, sedimentation may reach 10 to 20 percent in fine-grained estuaries, but only 0 to 2 percent along high energy coasts having very coarse-grained bottom sediments. Similarly, along sandy beaches the stranding of oil along the shoreline may reach 25 to 35 percent, as compared to only 1 to 2 percent along steep, rocky coasts. Dissolution, in general, does not vary so radically, being approximately 10 to 15 percent along high-energy rocky coasts, as compared to 5 to 10 percent in sheltered estuaries that do not have the mixing energy to drive additional oil into the water column.

Sediment origins across the terrestrial-aquatic continuum: climate threat mitigation and promotion of water quality

2020 ◽  
Author(s):  
Katy Wiltshire ◽  
Toby Waine ◽  
Bob Grabowski ◽  
Miriam Glendell ◽  
Steve Addy ◽  
...  
Keyword(s):  
Water Quality ◽  
Soil Erosion ◽  
Soil Loss ◽  
River Channel ◽  
River Channels ◽  
Catchment Scale ◽  
Transport Pathways ◽  
Fine Grained ◽  
Erosion Rates ◽  
Erosion Modelling

&lt;p&gt;Although fine-grained sediment (FGS) is a natural component of river systems, increased fluxes can impact FGS levels to such an extent they cause detrimental, irreversible changes in the way rivers function intensifying flood risk and negatively affecting water quality.&lt;/p&gt;&lt;p&gt;Previous catchment scale studies indicate there is no simple link between areas of sediment loss and the organic carbon (OC) load in waterways; areas with a high soil loss rate may not contribute most sediment to the rivers and areas that contribute the most sediment may not contribute the most OC. Anthropogenic and climate changes can accelerate soil erosion and the role of soil OC transported by erosional processes in the fluxes of C between land, water and atmosphere is still debated. Tracing sediment pathways, likely depositional areas and connections to streams leads to better assumptions about control processes and better estimation of OC fluxes.&lt;/p&gt;&lt;p&gt;In this innovative study OC fingerprinting of sediment reaching a catchment&amp;#8217;s waterbodies is combined with OC stock and erosion modelling of the terrestrial catchment. Initial results show disconnect between catchment OC loss erosion modelling and fingerprinting results, which could be due to failure to model connectivity between the land and river channel. The current soil erosion model RUSLE (Revised Universal Soil Loss Equation) calculates only the spatial pattern of mean annual soil erosion rates. Using the WaTEM SEDEM model, which in includes routing (and possible en route deposition) of eroded sediments to river channels, we aim to determine the dominant source of OC within catchment streams by identification of both the land-use specific areas with the highest OC loss and the transport pathways between the sources and river channel.&lt;/p&gt;

Influence of wind, wave, and water level dynamics on walleye eggs in a north temperate lake

2015 ◽  
Vol 72 (4) ◽  
pp. 570-581 ◽  
Author(s):  
Joshua K. Raabe ◽  
Michael A. Bozek
Keyword(s):  
Water Level ◽  
Wave Energy ◽  
Wind Wave ◽  
Abiotic Factors ◽  
Critical Factor ◽  
Fine Sand ◽  
Water Levels ◽  
Water Level Fluctuations ◽  
Egg Survival ◽  
Wave Velocities

Walleye (Sander vitreus) populations are cyclic because of biotic and abiotic factors, and wind activity, wave energy, and water levels may be influential given walleye spawn close to shore. We installed an anemometer and tridirectional velocimeter on a spawning reef in Big Crooked Lake, Wisconsin, in 2005 to determine wind–wave relationships and wave energy exceedance of critical velocities of both egg (affecting transport) and substrates (affecting abrasion or burial). To evaluate egg movement, we delineated egg locations at adhesive, postspawn, and black-eyed stages and surveyed on-shore for stranded eggs. We monitored water level with a staff gauge. Wind and wave velocities were significantly (p < 0.01) correlated, and wave velocities were significantly higher (p < 0.01) nearshore (2.0 m) than further from shore (4.6 m). Mean nearshore wave velocities were often sufficient to initiate movement of nonadhesive eggs (45% of records) and fine sand (39%) during egg incubation. Surveys indicated waves moved eggs closer to shore and some onto shore. Water level fluctuations (range = 2.4 cm) likely did not strand or desiccate eggs. We documented that wind and wave activity transports eggs and substrates and should be considered a critical factor in annual walleye egg survival and year-class strength.

scholarly journals THE FLUVIAL ACTION OF THE KARLA BASIN STREAMS IN A NATURAL AND MAN – MADE ENVIRONMENT

2017 ◽  
Vol 43 (2) ◽  
pp. 706
Author(s):  
Ch. Moumou ◽  
Κ. Vouvalidis ◽  
S. Pechlivanidou ◽  
P. Nikolaou
Keyword(s):  
Water Level ◽  
Historical Data ◽  
Laser Range Finder ◽  
Gis Analysis ◽  
Fine Grained ◽  
Second Stage ◽  
Base Level ◽  
Fine Grained Material ◽  
Local Base ◽  
Lake Karla

This study investigates the fluvial action of streams draining the Lake Karla basin, located in the plain of Thessaly, in Central Greece. Until a few decades ago, a large part of this area had been occupied by a lake. In order to find out the relation between the channel bed morphology and the oscillations of the local base level due to variations in water level and human intervention in the lake, the following streams were investigated: the flumes of Mpegiatiko, Bagiorema, Bathurema, Xerias and Maurorema. The width and the length of all channels were measured with a laser range finder while the incision and the erosive events were recorded by GPS with sub-meter accuracy. Furthermore, an integrated GIS analysis was undertaken in order to illustrate the changes in the water level of Lake Karla coupled with historical data and data from previous studies. It will be shown that there were two main evolutionary stages which controlled the local base level changes of the studied area. The first one is connected to the continuous changes in the lake’s water level and its reduction from 64m to 45m a.s.l. This resulted in the incision of the channels and the creation of characteristic knick points upstream. The second stage is associated with the draining of Lake Karla in 1962. This intervention mostly altered the streams that developed into fine-grained material channel beds.

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