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Times Advocate, 1992-08-05, Page 22ONO Shoreline eroshn is both above and below water By Patrick Donnelly GRAND BEND - The water level of the Great Lakes vary on a daily, seasonal, and yearly basis. To some degree, this fact separates the Great Lakes from the ocean coasts which have a more predictable tidal change and which do not have the wide yearly fluctuations that the Great Lakes do. Lake Huron, spe- cifically, has a typical seasonal fluctuation of 0.4 metres from the monthly low in March to the monthly high in September. In 1986, Lake Huron was 0.8 me- tres higher than the long term aver- age for this lake, or almost 2.0 me- tres higher than the record low water level recorded for Huron in 1964. Coastal researchers have tried an- alyzing lake level changes and cal- culating a "cycle" of low and high levels. The levels can be described as cyclical, however defining them as following a 7, 15, or 20 year cy- cle in more difficult. Shoreline erosion (above water): In the bluff region north of Grand Bend, erosion by wave action at the bluff base, or "toe", can cause steepening of the point where the bluff becomes unstable and bluff failure, or "slumping" occurs in large sections off the bluff. Some bluff areas are more prone to this type of bluff failure than other de- pendent upon the offshore depth of water and bluff composition. How- ever,- it can be seen that during higher lake levels, this wave action acting upon the bluff toe will occur more often It is known fmni previous re- search that bluff erosion does not occur consistently from year to year, but does respond to the steep- ening actions which cause bluff in- stability. Therefore, an actively eroding bluff may experience sev- eral years of no evident erosion at all from the bluff top, or crest. Of- ten, however, movement of the bluff material part of the way down the slope or at the toe will go unno- ticed and not be considered when suddenly a large portion of the bluff will fail. This large and obvi- ous movement of the bluff may be as a result of the earlier, smaller events which tend to steepen the overall bluff and cause instability. Therefore, as an example, a bluff described as experiencing erosion at a rate of 0.6 metres per year may have no apparent erosion for five years and then three metres is erod- Genetically engineered soybeans to be field tested GUELPH - Transgenic plant field testing is expanding this summer at the Elora Research Station to in- clude genetically engineered soy- beans. The soybeans join several varie- ties of transgenic alfalfa and cano- la, developed by crop scientists in Guelph, Europe and the United States, being evaluated for their ability to perform under field con- ditions. The tests include 200 10 -square - metre plots of canola, • 70 1.5 - square -metre plots of alfalfa and 24 10 -square -metre plots of soybeans. The plants are transgenic because they contain genes not normally as- sociated with their species. The al- falfa plant:, for example, have stress -tolerant genes (alcohol dehy- drogenase in one line, superoxide dismutase in the other) obtained from members of the canola and to- bacco family. The transgenic cano- ia plants are carrying laboratory - engineered microbial genes that may be useful in aiding hybrid seed production and improving weed control with fewer applied herbi- cides. -The soybeans have a built-in resistance to herbicides. "Recent advances and discoveries in molecular biology and plant cell biology have provided opportuni- ties for improving plant quality and agronomic characteristics through gene transfer," says Prof. Wally Be- versdorf, chair of the Department of Crop Science. "Individually, these transgenic lines have the po- tential to improve important charac- teristics of alfalfa and canola." Beversdorf says field testing is a normal and essential step in the de- velopment of new varieties. "Showing great promise in the la- boratory is not enough" he says. "New potential varieties must be able to withstand the rigors of ex- posure to the elements, which can't be adequately simulated indoors." Field experiments of modified plants are conducted according to experimental procedures and re- search approvals required by the Plant Health Directorate of Agricul- ture Canada. Beversdorf says the procedures are intended to prevent the movement of experimental plant material into both the food chain and the natural environment_ The University of Guelph is one of the first institutions in Canada to field test transgenic plants, he says, and the progress is encouraging. "Some of the results have been excellent, but we need to do more testing. It's still too early to say how these plants will perform on the farm." i)onalc 10 lilts trip ed in one event in the sixth year. Sborelloe Erosion (below water): It has also become apparent from re- cent Great Lakes shoreline research that the erosion of the bluffs coin- cides, or is controlled by, erosion of the lakebottom near the shoreline where the waves break (also termed the "nearshore"). This factor is a very important consideration when shore protection is being proposed because it will influence the design parameters (i.e. size and depth) of the protection structure. This lower- ing of the nearshore lakebottom will occur during periods of lower lake levels when waves will break and dissapate energy offshore. Then, when lake levels again rise, the deeper lakebottom will permit larger waves to break closer to the shore resulting in an increased erosive power of the waves along the shore- line. Erosion will occur until an equilibrium is reached between the water level, depth of the nearshore, and location of the bluff toe. Some areas of the Ausable Bay- field Conservation Authority shore- line benefit from a more resistant till material contained within the bluff and nearshore lakebottom composi- tion. This till, which is known as the Rannoch Till, forms a natural pro- tection to water erosion. These areas are therefore more stable with re- gards to shoreline change and the occurrence tit' this erosion resistant till influences the shoreline configu- ration (i.e. they form "points of land" such as Dewey Point, Hay Township and Rocky Point, Stanley Township). This process of nearshore lakebot- tom lowering, followed by increased wave attack at the shoreline and bluff adjustment, is a continuous process which may take many years to reach an equilibrium It is however an important process which must be understood and re - silted when shoreline protection works are being anticipated and the type of protection structure is be- ing considered. Unfortunately, ht. de is known about the rate of near - shore lakebottom lowering along the ARCA shoreline due to limited historical information on the near - shore lakebottom. What does this mean to bkeshore owners? Erosion, both above and below the waterline, is a natural process which is occurring in various de- grees over most of the ARCA shoreline. An understanding of the processes will enable landowners to consider the limitations which exist for "controlling" them. This is especially true when the topic of shore protection is discussed. 1t is also evident that erosion will continue regardless of whether or not lake levels are controlled to some degree. This is what prelimi- nary findings from the Internation- al Joint Commission CDC) research is suggesting. Storm damage along the Lake- shore beach and bluff areas can be reduced by protection measures in- stalled with 'consideration for prop- er design and adjacent property ef- fects. The protection will not reduce the erosion of the nearshore lidrebottom and may increase the water depths immediately lake - ward of the proposed structure, once installed, due to localized ero- sion effects. If the appropriate con- sideration are not made in the de- sign, the very beach which the landowner is attempting to pmtect may be eroded away because of the existence of the new erosion protection structure. These factors need to be carefully assessed when considering shore protection struc- tures. 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