Frequency Of Storm Events Research Articles

Slowly but steadily, a stormier Europe

One anticipated consequence of global warming is a rise in the strength and frequency of wind storms striking Europe, bringing about associated increases in property damage, choppy seas, and coastal flooding. Previous research, mostly based on long‐term pressure observations, has sought, to no avail, the signal of a persistent increase in European storms. Using the 20th Century Reanalysis, a recently developed atmospheric reconstruction stretching back to 1871, Donat et al. identified a significant increase in both the strength and frequency of wintertime storms for large parts of Europe. For six regions spread across Europe the authors calculated two different measures of storminess: the magnitude of extreme wind speeds and the frequency of storm events. They found a distinct increase in wind storm activity since the late nineteenth century. The authors also found that regional increases in storm frequencies and extreme wind speeds showed a gradient across Europe, with the largest increases in the northwest, near western Norway, decreasing toward the edge of the study area in central Germany. They found an average increase in storm frequency of between 0.1 and 0.5 storm day per year per decade for the different regions, corresponding to 1.4–6.8 additional storm days per year over the course of the study period, which they suggest could be attributed to global warming or natural variability. (Geophysical Research Letters, doi:10.1029/2011GL047995, 2011)

Present and future challenges of urban systems affected by seawater and its intrusion: the case of Venice, Italy

In lagoonal and marine environments, both historic monuments and recent buildings suffer from severe salt damage caused by sea flooding, sea-level rise and frequent storm events. Salt-water contamination of groundwater systems, a widespread phenomenon typical of coastal areas, can lead to a deterioration not only of the quality of fresh groundwater resources, but also of building materials in urban settlements. A general overview is given of the hydrogeological configuration of the subsoil of Venice (Italy), with particular reference to the shallow groundwater circulation. The relationship between the seawater in the subsoil and salt decay processes, due to salt crystallization, is highlighted. These processes affect civil constructions in Venice’s historic center. Perched aquifers, influenced by tide variations and characterized by salt-water intrusion, favor the transport of salts within masonry walls through the action of rising damp. In fact, foundations, in direct contact with the aquifers, may become a preferential vehicle for the transportation of salt within buildings. Decay patterns of different building materials can be detected through non-destructive techniques, which can identify sea-salt damage and therefore assist in the preservation of cultural heritage in coastal areas.

Integrated analysis of water quality parameters for cost-effective faecal pollution management in river catchments

In many parts of the world, microbial contamination of surface waters used for drinking, recreation, and shellfishery remains a pervasive risk to human health, especially in Less Economically Developed Countries (LEDC). However, the capacity to provide effective management strategies to break the waterborne route to human infection is often thwarted by our inability to identify the source of microbial contamination. Microbial Source Tracking (MST) has potential to improve water quality management in complex river catchments that are either routinely, or intermittently contaminated by faecal material from one or more sources, by attributing faecal loads to their human or non-human sources, and thereby supporting more rational approaches to microbial risk assessment. The River Ouse catchment in southeast England (U.K.) was used as a model with which to investigate the integration and application of a novel and simple MST approach to monitor microbial water quality over one calendar year, thereby encompassing a range of meteorological conditions. A key objective of the work was to develop simple low-cost protocols that could be easily replicated. Bacteriophages (viruses) capable of infecting a human specific strain of Bacteroides GB-124, and their correlation with presumptive Escherichia coli, were used to distinguish sources of faecal pollution. The results reported here suggest that in this river catchment the principal source of faecal pollution in most instances was non-human in origin. During storm events, presumptive E. coli and presumptive intestinal enterococci levels were 1.1–1.2 logs higher than during dry weather conditions, and levels of the faecal indicator organisms (FIOs) were closely associated with increased turbidity levels (presumptive E. coli and turbidity, r = 0.43). Spatio-temporal variation in microbial water quality parameters was accounted for by three principal components (67.6%). Cluster Analysis, reduced the fourteen monitoring sites to six representative ‘sentinel’ sites. The correlation coefficient between presumptive E. coli and phages of Bacteroides GB-124 was very small ( r = 0.05) whilst that between turbidity and suspended solids was high ( r = 0.62). Variations in climate, animal and anthropogenic interferences were all, either directly or indirectly, related to faecal contamination. The findings show the importance of meteorological conditions, such as storm events, on microbial water quality, and suggest that any future increases in the frequency of storm events (associated with climate change) are likely to result in a greater incidence of FIO/pathogen loads. This low-cost approach could help to predict spatio-temporal ‘hotspots’ of elevated waterborne disease risk. The work also represents an important step towards integrating novel MST tools into river catchment modelling.

Paleoenvironmental implications of an extensive maceriate microbialite bed in the Furongian Chaomidian Formation, Shandong Province, China

This study focuses on the unique occurrence of an extensive microbialite bed (10–20 m thick) in the Chaomidian Formation (Furongian) in Shandong Province, China in order to understand its paleoenvironmental implications. The microbialite bed can be traced for over 6000 km 2 in area. The microbialites are characterized by centimeter- to decimeter-scale branching maze-like constituents (maceriae) of microbial and muddy sediments with chaotic texture, including tabular maceriate microbialite (type 1), columnar maceriate microbialite (type 2), and columnar chaotic microbialite (type 3). Within the bed, each microbialite unit is generally well correlated for tens of kilometers. The entire bed is bounded by limestone–marlstone alternation at the base, and an erosional surface at the top that is subsequently overlain by a grainstone bed of various thicknesses. The microbialite bed formed when the seafloor reached suitable water depth for the microbial growth during sea-level rise accompanied with carbonate production. The maze-like maceria structures formed to acquire a larger surface area under a relatively large input of lime mud. The tabular maceriate microbialites initially formed in relatively deep-water environments and flourished on broad and flat seafloor, whereas the columnar microbialites (types 2 and 3) developed under the influence of strong waves and currents. The microbialite bed was eroded and terminated by frequent storm events and buried under the reworked grainstone. Further rise in sea level and increased metazoan activities afterwards limited the resurgence of microbes in the late Furongian.

Chemical fluxes in time through forest ecosystems in the UK – Soil response to pollution recovery

Long term trend analysis of bulk precipitation, throughfall and soil solution elemental fluxes from 12 years monitoring at 10 ICP Level II forest sites in the UK reveal coherent national chemical trends indicating recovery from sulphur deposition and acidification. Soil solution pH increased and sulphate and aluminium decreased at most sites. Trends in nitrogen were variable and dependant on its form. Dissolved organic nitrogen increased in bulk precipitation, throughfall and soil solution at most sites. Nitrate in soil solution declined at sites receiving high nitrogen deposition. Increase in soil dissolved organic carbon was detected – a response to pollution recovery, changes in soil temperature and/or increased microbial activity. An increase of sodium and chloride was evident – a possible result of more frequent storm events at exposed sites. The intensive and integrated nature of monitoring enables the relationships between climate/pollutant exposure and chemical/biological response in forestry to be explored.

Application of bivariate frequency analysis to the derivation of rainfall–frequency curves

Bivariate distributions have been recently employed in hydrologic frequency analysis to analyze the joint probabilistic characteristics of multivariate storm events. This study aims to derive practical solutions of application for the bivariate distribution to estimate design rainfalls corresponding to the desired return periods. Using the Gumbel mixed model, this study constructed rainfall–frequency curves at sample stations in Korea which provide joint relationships between amount, duration, and frequency of storm events. Based on comparisons and analyses of the rainfall–frequency curves derived from univariate and bivariate storm frequency analyses, this study found that conditional frequency analysis provides more appropriate estimates of design rainfalls as it more accurately represents the natural relationship between storm properties than the conventional univariate storm frequency analysis.

Sensitivity of post‐hurricane beach and dune recovery to event frequency

AbstractThe recovery of Santa Rosa Island in northwest Florida is characterized following Hurricane Katrina (September 2005), which was preceded by Hurricanes Ivan (2004) and Dennis (2005). Beach and dune recovery were quantified to the east and west of Pensacola Beach through a comparison of LiDAR data collected immediately following Hurricane Katrina and in July 2006 after almost a year of recovery. East of Pensacola Beach (the Santa Rosa Unit), the shoreline retreated by an average of 64 m during the 2004–2005 hurricane season and recovered by an average of 19 m. To the west of Pensacola Beach (the Fort Pickens Unit), the shoreline retreated by an average of 30 m, and while no significant shoreface recovery was observed, the presence of vegetation on low‐profile dunes promoted backshore accretion. It is found that beachface recovery in the Santa Rosa Unit and backshore accretion in the Fort Pickens Unit occurred at the widest sections of the island where the pre‐storm profile volume had been relatively large and overwash penetration was at a minimum. The narrow sections of the island (between cuspate headlands) had a smaller profile volume before the storms, leading to greater overwash penetration and in some cases island breaching in both sections, which limited the volume of sediment available for shoreface recovery. The alongshore variation in recovery is not only related to the island width, but also the offshore bathymetry, height of the pre‐storm dunes and the overwash penetration. If sufficient time is allowed for the return of vegetation and the recovery of the dunes, the variations in storm impact observed during Hurricane Ivan will be reinforced during subsequent storms. In this respect, the level of impact during subsequent storms and the ability of the island to recover will depend on the frequency of storm events. Copyright © 2009 John Wiley & Sons, Ltd.

Treatment Performance of an Extensive Vegetated Roof in Waterloo, Ontario

Abstract Vegetated roof technologies are used as treatment measures to mitigate the effects of urban stormwater. A mass balance approach was used to assess the treatment performance of a vegetated roof located on the City Hall in Waterloo, Ontario. The vegetated and control roof sections were instrumented to measure precipitation, storage, and outflow for 18 storm events from June to October, 2006. Concentrations of suspended solids, total phosphorus (TP), and SRP (SRP) in precipitation and roof (vegetated and control) runoff were measured. A total of 155.6 mm of rain fell during the study period. The vegetated roof retained 64.5 mm (43.9%) of the total rainfall while the control roof retained approximately 5.1 mm (4.0%). For individual rain events, the vegetated roof retained an average of 3.5 mm (47.6%), while the control roof retained approximately 0.3 mm (4.7%). Water retention varied with storm size, season, and frequency of storm events. The vegetated roof retained 80.1% of precipitation for storm events ≤3.5 mm, and 34.9% for storm events >3.5 mm. TP and SRP concentrations from the vegetated roof were significantly higher than either the precipitation or runoff from the control roof.

A Statistical Approach to Modelling the Temporal Patterns of Ocean Storms

The world's sandy beaches, already eroding at rates of concern to coastal managers, are facing a further threat based on predictions of global climate change. Although mean sea level rise has long been recognized as a likely consequence of climate change, it has been suggested that there may also be a change in ocean storminess—that is, the intensity and frequency of storm events. While the effects of a change in wave height can be handled with existing analysis methods, the effects of a change in the rate at which storms arrive are less obvious and harder to predict. As a prelude to model studies investigating coastal response to changes in storminess, it is necessary to have a reliable method for generating storm and wave histories that contain waves that not only conform to known distributions of height and period but that also arrive at the proper rate in time.In the current work a statistical model of the arrival rate of storms and the wave heights within those storms has been developed. Storminess can be modelled by describing interstorm period, storm duration, the average wave height, and the temporal distribution of storm significant wave heights using methods that have been applied in rainfall modelling. The model has been verified against existing wave climate parameters of wave exceedence and wave persistence, and it has been shown to reproduce these statistics reliably.

Climate and environment reconstruction during the Medieval Warm Period in Lop Nur of Xinjiang, China

We made multi-proxy analysis of 14C, grain size, microfossils, plant seeds, and geochemical elements on samples from a profile in the central West Lake of Lop Nur. The grain size suggests relatively stable sedimentary environment around the Medieval Warm Period (MWP) with weak storm effect, which is followed by frequent strong storm events. Abundant microfossils and plant seeds in this stage indicate a warm and humid fresh to brackish lake environment. C, N, and stable elements are high in content in the sediments while Rb/Sr, Ba/Sr, and Ti/Sr are in a steady low level. In addition, plenty of red willows lived here prior to about 700 a B.P., indicating a favorable environmental condition. The results indicate that the environment in Lop Nur and its west bank turned to be favorable at about 2200 a B.P., where the Loulan Culture began to thrive. Then the climate and environment came to be in the good condition in the Tang and Song Dynasties, when the storm effect became weaker, rainfall increased and the salty lake water turned to be brackish to fresh lake water. Hence, limnic biomass increased with higher species diversity.

Seasonal variations of dust record in the Muztagata ice cores

Based on the oxygen isotope ratio and microparticle record in ice cores recovered at Mt. Muztagata, Eastern Pamirs, the seasonal variations of atmospheric dust have been reconstructed for the past four decades. High dust concentrations and coarser particle grains have the similar trend with oxygen isotope value. Our statistical results indicate that 50%–60% high dust concentration samples occur during the season with high oxygen isotope values (summer), while low dust storm frequency during spring and winter. Back-trajectory analysis shows that the air mass hitting Muztagata predominately came from West Asia (such as Iran-Afghanistan Plateau) and Central Asia, which are the main dust source area for Muztagata. Dust storms in those source areas most frequently occur during summer (from May to August), while frequent dust storm events in northern China mainly occur during spring (March to May). Regions in the path of Asian dust transport, such as in Japan, the North Pacific, and Greenland, also show high dust concentrations during spring (from March to May). Our results indicate that dust storms have different seasonality in different regions within Asia.

Seasonal accretion and erosion patterns of a microtidal sandy beach

Monthly elevation surveys of a 1.5 km stretch of coast at Noordwijk, the Netherlands, were made (1) to quantify seasonal variability in the cross-shore position of high-, mean- and low-tide contours, beach width and beach volume, and (2) to examine the dependence of the variability on the offshore wave characteristics. Additionally, daily cross-shore positions of contours obtained from video images were used to examine daily beach response to wave characteristics between successive surveys. The more intense and frequent storm events in winter than in summer resulted in a seasonal change from a wide beach with a small volume at the end of winter to a narrow, large-volume beach in summer. The seasonal pattern in beach width resulted from the cross-shore sediment exchange between the supratidal and lower-intertidal part of the beach. In contrast to the coupling between beach behaviour and wave characteristics on a seasonal scale, beach variability between successive surveys was unrelated to day- to week-averages of the preceding offshore wave conditions partly due to the precise timing of a storm relative to the two survey moments. Moreover, daily variability determined from the video images showed that differing antecedent morphology to storms and alongshore variations in beach morphology contributed to spatially and temporally variable beach response.

Wave-Sediment Interactions on an High Energy Beach System

Please click here to download the map associated with this article. The North coast of Northern Ireland is exposed to high-energy swells and frequent storm events and therefore beach systems found along this coast tend largely to be dissipative in character. Bedrock-framed coastlines formed by basalt cliffs, shore platforms and smaller sandy embayments dominate this study area. West Strand beach at Portrush (located 55°12′N/6°40′W) is a high-energy system shaped by a headland-embayment with a sandy beach to the north and boulder beach to the south. It is characterised by a microtidal regime and predominant local winds are west and south westerly. The research work aims to examine this high-energy beach under multiple storm scenarios and to investigate hydrodynamic and morphodynamic behaviour at the site. For the analysis, a wave propagation model was used to compare wave energy dissipation from storm wave events as well as examining currents and sediment transport through the analysis of the spatial distribution of radiation stress. Real data from deep-water wave parameters (significant wave height, period and direction), wind direction and speed, and recent high-resolution bathymetry data were used as an input to the propagation model. The methodology was applied to West Strand beach (9 km2) at a scale of 1:250.

Closure of “Watershed-Scale Evaluation of a System of Storm Water Detention Basins” by Clay H. Emerson, Claire Welty, and Robert G. Traver

I consider this paper to be one of the most significant papers published in the past 10 years in the wateror hydrology-related journals of ASCE. That judgment is strongly influenced by the potential impact that its findings should have on correcting a widely applied but erroneous practice that has become—perhaps unwittingly—endemic certainly in Australia and presumably in the United States. I refer to the “sizing” of detention basins, used to mitigate mainstream flooding in developing urban catchments, by using tC “site time of concentration” instead of the catchmentwide “critical storm duration,” TC, used as the dominant storm duration in design. The two durations—tC and TC—in any given set of circumstances may differ by factors of two, four, eight or more; the derived rainfall depth differences and consequently the detention storage volume differences may be around two or three times. Widespread current practice therefore leads to undersized basins. The thoroughness of the authors in their quest to study the consequences of these differences, coupled with their professionalism in applying state-of-the-art techniques survey, measurement, model validation, etc. to a substantial field system in western Philadelphia, leaves no room for the skeptic to doubt the outcomes. Detention basin volumes fixed according to site-critical storm duration tC leads to minimal—the authors claim an average of 0.3%—mainstream peak flood reduction and, in some circumstances, peak flow increase, an even more daunting prospect. The authors conclude that “...on-site detention basins do not affect watershed-wide storm hydrographs resulting from frequent storm events.” This judgment I consider to be harsh as a generalization but certainly warranted for any system of undersized basins, as previously reviewed. A more favorable outcome—for detention adherents—may follow where basin volumes are fixed by using TC as the principal design parameter. The professional situation implied by the above considerations and the question of how it has developed is interesting to contemplate. In Australia—where anecdotal evidence suggests that 80% of basins are undersized—it stems from the municipal-agency approval process that accepts the tC-based design as satisfactory. The conscientious consulting engineer then faces a serious professional dilemma: should he or she design the basin correctly using TC , leading to greater cost for the developer, who is unlikely to be sympathetic and no support for a design based on “TC” from the Council officer for whom “what we’ve always done before” is the best guide. It is not surprising, given these

Preliminary notes on soft-bodied fossil concentrations from the Early Cambrian Chengjiang deposits

The efforts of labor-intensive collecting in the Early Cambrian Chengjiang deposits in eastern Yunnan Province, China led to the discovery of many horizons containing exceptionally well preserved soft-bodied fossil concentrations, many of which can be assigned to either monospecific concentrations or paucispecific concentrations. The features of these fossil concentrations support the hypothesis that frequent storm events producing tempestites mainly contributed to the preservation of abundant soft- bodied fossils in the Chengjiang deposits, and indi- cate that the balance of the ecological web in this region was probably frequently destroyed or upset by such storm events during that geological time. Ani- mals in a fossil assemblage in such fossil concentra- tions probably occupied similar ecological biotopes.

Investigating hydrologic alteration as a mechanism of fish assemblage shifts in urbanizing streams

Stream biota in urban and suburban settings are thought to be impaired by altered hydrol- ogy; however, it is unknown what aspects of the hydrograph alter fish assemblage structure and which fishes are most vulnerable to hydrologic alterations in small streams. We quantified hydrologic variables and fish assemblages in 30 small streams and their subcatchments (area 8-20 km 2 ) in the Etowah River Catchment (Georgia, USA). We stratified streams and their subcatchments into 3 landcover categories based on imperviousness (,10%, 10-20%, .20% of subcatchment), and then estimated the degree of hydrologic alteration based on synoptic measurements of baseflow yield. We derived hydrologic variables from stage gauges at each study site fo r1y( January 2003-2004). Increased imperviousness was positively correlated with the frequency of storm events and rates of the rising and falling limb of the hydrograph (i.e., storm ''flashiness'') during most seasons. Increased duration of low flows associated with impervi- ousness only occurred during the autumn low-flow period, and this measure corresponded with increased richness of lentic tolerant species. Altered storm flows in summer and autumn were related to decreased richness of endemic, cosmopolitan, and sensitive fish species, and decreased abundance of lentic tolerant species. Species predicted to be sensitive to urbanization, based on specific life-history or habitat require- ments, also were related to stormflow variables and % fine bed sediment in riffles. Overall, hydrologic variables explained 22 to 66% of the variation in fish assemblage richness and abundance. Linkages be- tween hydrologic alteration and fish assemblages were potentially complicated by contrasting effects of elevated flows on sediment delivery and scour, and mediating effects of high stream gradient on sediment delivery from elevated flows. However, stormwater management practices promoting natural hydrologic regimes are likely to reduce the impacts of catchment imperviousness on stream fish assemblages.

Investigating hydrologic alteration as a mechanism of fish assemblage shifts in urbanizing streams

Stream biota in urban and suburban settings are thought to be impaired by altered hydrology; however, it is unknown what aspects of the hydrograph alter fish assemblage structure and which fishes are most vulnerable to hydrologic alterations in small streams. We quantified hydrologic variables and fish assemblages in 30 small streams and their subcatchments (area 8–20 km2) in the Etowah River Catchment (Georgia, USA). We stratified streams and their subcatchments into 3 landcover categories based on imperviousness (<10%, 10–20%, >20% of subcatchment), and then estimated the degree of hydrologic alteration based on synoptic measurements of baseflow yield. We derived hydrologic variables from stage gauges at each study site for 1 y (January 2003–2004). Increased imperviousness was positively correlated with the frequency of storm events and rates of the rising and falling limb of the hydrograph (i.e., storm “flashiness”) during most seasons. Increased duration of low flows associated with imperviousness only occurred during the autumn low-flow period, and this measure corresponded with increased richness of lentic tolerant species. Altered storm flows in summer and autumn were related to decreased richness of endemic, cosmopolitan, and sensitive fish species, and decreased abundance of lentic tolerant species. Species predicted to be sensitive to urbanization, based on specific life-history or habitat requirements, also were related to stormflow variables and % fine bed sediment in riffles. Overall, hydrologic variables explained 22 to 66% of the variation in fish assemblage richness and abundance. Linkages between hydrologic alteration and fish assemblages were potentially complicated by contrasting effects of elevated flows on sediment delivery and scour, and mediating effects of high stream gradient on sediment delivery from elevated flows. However, stormwater management practices promoting natural hydrologic regimes are likely to reduce the impacts of catchment imperviousness on stream fish assemblages.

Spatial and temporal distribution of calcareous nannofossils along a proximal–distal transect in the Lower Jurassic of the Umbria–Marche Basin (central Italy)

Three Upper Pliensbachian/Lower Toarcian successions of the Umbria–Marche Basin were analysed for sedimentology and calcareous nannofossil content across a 120-km-long transect from proximal to distal areas with respect to the shallow Latium–Abruzzi Platform. The uppermost part of the Corniola Unit (Uppermost Pliensbachian) and the Marne di Monte Serrone Formation (p.p., Lower Toarcian; Polymorphum to Levisoni Ammonite Zones) that contains organic matter-rich levels were studied in the three localities. The analysis of the sedimentary structures in the studied successions indicates that the basin was a shallow-water system, above storm-wave base, during the Late Pliensbachian/Early Toarcian. The stratigraphic evolution of the sedimentary structures recorded in the studied localities shows that the Upper Pliensbachian corresponded to a regressive sedimentary interval, whereas a complete transgressive–regressive relative sea-level cycle occurred during the Lower Toarcian Polymorphum Zone. A further transgression occurred in the lowermost Levisoni Zone (Lower Toarcian). Changes from carbonate-dominated to marl-dominated sediments form decimetre- to metre-scale lithological units, that can be correlated from succession to succession, and may have resulted from short-term sea-level and/or palaeoenvironmental variations. The mean duration of these lithological units suggests that they formed in tune with the first orbital eccentricity cycle (100 ka). The analysis of calcareous nannofossil quantities (abundance per mm 2 of the smear slide, percentage, mean abundance) shows both spatial and temporal changes in the community structure. Schizosphaerella spp. and Crepidolithus crassus were more abundant in proximity to the shallow Latium–Abruzzi Platform. These two taxa were likely affiliated to oligotrophic conditions in marine surface waters, explaining why they were generally more abundant in carbonate-rich intervals than in marls. Mitrolithus jansae is interpreted as being a deep-dwelling species, which was more abundant during rising sea level in the earliest Toarcian. Species of the genera Lotharingius, Biscutum and Calyculus were more abundant when higher trophic conditions occurred, and were thus more common during periods of marl deposition. The stratigraphic distribution of calcareous nannoplankton and its interpretation in terms of palaeoecological affinities allow three main phases in the environmental evolution during the Early Toarcian anoxic event to be recognised. The first phase corresponds to a long-term transgression, and high-nannoplankton abundance in distal areas (mainly Lotharingius, Biscutum and Calyculus species) suggests high productivity that may have resulted from upwelling. The beginning of accumulation and preservation of organic matter in the sediments occurred during this phase. The scarcity of nannoplankton during the second phase may indicate oligotrophic conditions in surface waters, possibly due to water stratification during the highest sea-level stand. A high abundance of Schizosphaerella spp. and C. crassus is recorded in proximal areas, probably resulting from sporadic nutrient input from continental or shallow-platform areas. The maximum of organic matter preservation is recorded during this phase. During the third phase, relative sea-level fall and efficient water mixing by frequent storm events led to enhanced nannoplankton productivity in proximal and distal areas and to a decrease in organic matter accumulation in the Umbria–Marche Basin.

Development of Great Lakes shoreline management plans by Ontario conservation authorities

The Great Lakes shoreline in Ontario is subject to severe flooding and erosion due to frequent high water level periods and storm events leading to wind and wave action. After extensive property damages in 1985 and 1986, the province established a shoreline management program to be administered by the Ontario Ministry of Natural Resources. A key component of this program is the development of Great Lakes shoreline management plans by Ontario conservation authorities. A review of three such plans reveals a focus on understanding the range and frequency of shoreline flooding and erosion, and the use of land use regulations and shoreline protection structures to reduce the impact from these hazards. Limited attention and responses are provided for the range of issues and concerns that occur in these shoreline areas such as ecosystem management, species and habitat protection, and water quality. A lack of consistency, enforcement, monitoring and coordination occurs in the provincial program which has also recently been affected by related land use and environmental planning initiatives and government financial restraints.

河床付着生物膜現存量の周年変化と降雨に伴う剥離量の評価

In Hinuma River, changes of periphyton biomass were observed weekly from September 1987 to March 1990 to evaluate the dynamics of the periphyton biomass in the river. Periphyton were sampled from artificial substrates which were 10cm×10cm unglazed clay tiles. The tiles were submerged in the river more than one month before sampling.At the high periphyton biomass, the ratio of carbon per dry weight of periphyton was low because a significant amount of inorganic particles such as clay and silt was trapped in periphyton. However, the ratio of carbon : nitrogen : phosphorus remained constant regardless of the change of the biomass. From April to October the periphyton biomass was low due to losses by scouring due to frequent storm events. In November and December, the periphyton biomass became greatest because of steady low flow in the river. From January to March, the biomass did not increase significantly due to low temperature even though the rainfall was low.The scouring was found to be a main factor in the dynamics of the periphyton biomass in the river. The amount of the periphyton biomass (as carbon) after scouring was proportional to the exponent of the maximum flow during the storm.