Recent Geomorphic Evolution of Saltmarshes Ln
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RECENT GEOMORPHIC EVOLUTION OF SALTMARSHES LN CUMBERLAND BASIN, BAY OF FUNDY A Thesis Presented to The Faculty of Graduate Studies of The University of Guelph by ANGELA DAWN SCOTT In partial fulfilment of requirements for the degree of Master of Science May, 2000 O Angela Scott, 2000 National Library Bibliothèque nationale 1*1 of Canada du Canada Acquisitions and Acquisitions et Bibliographic Services services bibliographiques 395 Wellington Street 395. rue Wellington OtbwaON K1AON4 Ottawa ON KIA ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Libraiy of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la fome de microfiche/fïlm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protege cette thèse. thesis nor substantial extracts fiom it Ni Ia thèse ni des extraits substantiels may be printed or othenivise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. ABSTRACT RECENT GEOMORPHIC EVOLUTION OF SALTMARSHES IN TEE C-ERLAND BASIN, BAY OF FUNDY Angela Dawn Scott Advisor: University of Guelph, 2000 Professor J-Ollerhead Co-Advisor: Professor R. Davidson-Arnott Spatial and temporal variations in six ~umberladB asin saltmarsh margin and tidal creek patterns were measured and possible controls on their evolution explored at the decadal scale. Measurements of marsh change were made using aerial photograph sets fkom the 1940's - 1990's. Field measurements and historic weather data were used to explore possible controlling variables. It is clear that the Cumberland Basin saltmarsh system is very dynamic and that episodic changes are normal. Differences in saltmarsh morphology were found to be primarily a function of saltmarsh evolutionary stage and some key, site-specific extemal variables. A conceptual mode1 was developed to illustrate the evolutionary stage. The most important non-site-specific external variable studied is the relative 'stonniness' of a tïme penod. This is apparent fiom the overall retreat measured during the period 1960 - 1970. It was also found that the creek networks present in the saltmarsh and mudflat environments are quite stable in tems of location and morphology. This degree has provided me with new insights and expenences that were far beyond what 1expected. 1have completed my Masters degree only with the support of many ïndividuals. First, 1would like to thank my advisor, Jeff Ollerhead and co- advisor, Robin Davidson-Arnott. Your patience, fiiendship and understanding were greatly appreciated and will never be forgotten. Th& is dso given to my family and fifends who have always given me support and believed in my abilities even when 1didn't. A special thank-you to Ryan and Dree, you both lmow what you mean to me and 1couldn't have done this without you. Finally, 1could not have completed this project without the Eendship and hard work of my girls in the field. A special thanks to Rebecca Rush, Jaime Dawson and Michelle Zehr. The memories will last a lifetirne. This thesis is dedicated to people would have achieved dreams and an understanding of their true potential, regardless of the obstacles put in their way! TABLE OF CONTENTS ABSTRACT ACKNOWLEDGEMENTS TABLE OF CONTENTS LIST OF FIGURES LIST OF TABLES CHAPTER 1 RlESEARCH CONTEXT, PURPOSE AND OBJECTIVES 1 .O Introduction 1.1 The Importance of the Bay of Fundy Ecosystem 1.2 Rationale for the Research 1.3 Research Problem and Objectives The Field Work CHAPTER n STUDY SITE 2.0 Saltmarshes in the Bay of Fundy 2.2 Saltmarsh Location and Description Pecks Cove (1) Allen Creek (2) Minudie Point West (3) Fort Beauséjour (4) Amherst Point (5) Minudie Point East (6) CHAPTER III RESEARCH DESIGN AND METHODOLOGY 3.0 Introduction 3.1 Field Surveying and Sampling 3 -2 Field Mapping 3 -3 Laboratory Andysis Grain size ânalysis Water content andysis 3-4 External Variables: Climate Data 3.5 Aerial Photography Andysis Aerial Pho tography Geographic Information System (GIS) Techniques CHAPTER IV RESULTS 4.0 Introduction 49 4.1 Measurements of Margin and Tidal Creek Change Pecks Cove Marsh (1) Allen Creek Marsh (2) Minudie Point West Marsh (3) Fort Beauséjour Marsh (4) Amherst Point Marsh (5) Minudie Point East Marsh (6) Overall Change 4.2 Marsh Character Pecks Cove Mar& (1) Allen Creek Marsh (2) Minudie Point West Marsh (3) Fort Beauséjour Marsh (4) Amherst Point Marsh (5) Minudie Point East Marsh (6) Significant Differences in Marsh Character 4.3 Trends in Key Controlling Variables Estirnated Wave Heights Climatic Patterns Sediment Deposition Trends for Decadal Per-iods Site-Specific Extemal Variables CHAPTER V DISCUSSION, CONCLUSIONS AND RESEARCH OPPORTUNITIES 5.O Introduction 98 5.1 Signincance of Site-Specific Variables and Observed Changes 5.2 Significance of Key Controllhg Variables and Observed Changes 5.3 Indentifkation and Significance of Long-Term Trends Concephial Model 5 -4 Tidal Creek Movement 5.5 Conclusions 5.6 Research Opportunities REFERENCES APPENDICES LIST OF FIGURES Figure 1.1 Illustration of the general vegetation gradient of a saItrnarsh although the boundaries may Vary. Figure 1.2 The characteristics of saltmarshes are deterrnined by a wide range of physical and biological controls and processes. Figure 2.1 Mean tidal range in the Bay of Fundy region. Figure 2.2 Location map for the Bay of Fundy, Canada. hset shows the upper reaches. Figure 2.3 Range and variation of tidal amplitude in the Cumberland basin and elevation of major features (modifïed fiom Gordon and Cranford, 19 94). Figure 2.4 Map of Cumberland Basin showing the distribution of saltmarshes and intertidal mudflats. Marsh location are: 1) Pecks Cove; 2) Allen Creek; 3) Minudie Point West; 4) Fort Beauséjour; 5) Amherst Point; and 6) Minudie Point East (modified Eom Gordon et al., 1985). Figure 2.5 a) Location of topographic survey and field measurements at Pecks Cove; b) photograph of swey line looking landward. Figure 2.6 a) Location of topographic survey and field measurements at Allen Creek; b) marsh arrn at Men Creek; c) erosive marsh marecliff. Figure 2.7 a) Location of topographic sweyand field measurements at Minudie Point West; b) cliffed and erosive old marsh mare; c) extent of Iow marsh and new marsh edge infront of old rnarsh margin. Figure 2.8 Upper reaches of tidal creek at Minudie Point West. Tidal creeks drop off the marsh surface approximately 1 m. Figure 2.9 a) Profile view of topographic survey and field measurements area at Fort Beauséjour (note rnarsh margin arm in centre of photo); b) marsh margin cliff. Figure 2.10 a) Location of topographic survey and field measurements at Amherst Point; b) mudflat region at Amherst Point; c) low rnarsh margin. Figure 2.1 1 a) location of topographic survey and field measurernents at Minudie Point East; b) view north fiom survey he; c) mudflat cliff into Maccan River. Figure 2.12 a) Close up of the mudcracks present on Minudie Point East marsh; b) view north fiom survey line. Figure 3.1 A pIan view of the saltmarsh setup for topographic surveying, field measurements and reference line for measuring margin change (x-x). Figure 3.2 Tidd creek mapping with Trimble Pro XR GPS. Figure 3.3 Layout showing measurement o£marsh margin, marsh width and tidal creek movement, Figure 4.1 Pecks Cove marsh margin and tidal creek movernent fiom 1945 to 1999. Figure 4.2 Mean marsh margin change for six Cumberland Basin marshes fiom 1940 to 1999. Growth (+ve values) and/or recession (-ve values) dong the marsh margin are represented fiom one time penod to the next. Figure 4.3 Mean tidal creek movement for yearly periods in Cumberland Basin marshes. Significant movement are values > 8 m. Figure 4.4 Minudie Point West marsh margin movement Çom 1939 to 58 1999. Figure 4.5 Fort Beauséjour marsh margin and tidal creek movement 60 fiom 1962 to 1999. Figure 4.6 Minudie Point East tidal creek movement Eorn 1939 to 1999. 63 Figure 4.7 a) Mean marsh margin change for each time period; b) 64 amount of marsh margin change per year for each decadal tirne period. Figure 4.8 a) Mean marsh margin change values for the entire time 67 period (1940-1999); b) mean tidal creek movement for the entire time period (1 940- 1999). Figure 4.9 a) Mean tidal creek change for each theperiod; b) amount of tidal creek change per year for decadal tirne periods. Figure 4.10 a) Marsh and mudnat profiles; b) sediment composition; c) substrate shear strength values; and d) water content in percent at Pecks Cove. Figure 4.11 a) Marsh and mudfiat profiles; b) sediment composition; c) substrate shear strength values; and d) water content in percent at AUen Creek. Figure 4.12 a) Marsh and mudflat profiles; b) sediment composition; c) substrate shear strength values; and d) water content in percent at Minudie Point West. Figure 4.13 a) Marsh and mudflat profiles; b) sediment composition; c) substrate shear strength values; and d) water content in percent at Fort Beauséjour. Figure 4.14 a) Marsh and mudflat profiles; b) sediment composition; c) substrate shear strength values; and d) water content in percent at Amherst Point. Figure 4.15 a) Marsh and mudflat profiles; b) sediment composition; c) substrate shear strength values; and d) water content in percent at Minudie Point West. Figure 4.16 a) Line A profiles for al1 six saltmarshes; b) line B profiles for all six saltmarshes.