Fluvial Geomorphology and Culvert Assessment of the Meduxnekeag River Aroostook County, Maine Prepared for Houlton Band of Maliseet Indians Littleton, Maine Meduxnekeag River Prepared by Dr. John Field Field Geology Services Farmington, ME July 2010 Fluvial geomorphology and culvert assessment of the Meduxnekeag River watershed - July 2010 Page 2 of 154 Table of Contents EXECUTIVE SUMMARY................................................................................................5 1.0 INTRODUCTION........................................................................................................6 2.0 FLUVIAL GEOMORPHOLOGY ASSESSMENT.....................................................7 2.1 Map and aerial photograph interpretation.................................................................7 2.1a Watershed characterization................................................................................7 2.1b Historical changes............................................................................................10 2.2 Archival research....................................................................................................11 2.3 Mapping of channel features...................................................................................12 2.4 Topographic surveying of channel dimensions......................................................14 2.5 Conceptual restoration designs...............................................................................16 3.0 CULVERT ASSESSMENT .......................................................................................19 3.1 Topographic surveying...........................................................................................20 3.2 Measurement of particle sizes.................................................................................21 3.3 Identification of design measures...........................................................................21 3.3a Suiter Brook 1...................................................................................................22 3.3b Smith Brook 1....................................................................................................22 3.3c Pearce Brook 2 and Pearce Brook 3.................................................................22 3.3d Pearce Brook 4.................................................................................................23 3.3e Brown Brook 2..................................................................................................23 3.3f Brown Brook 3...................................................................................................23 3.3g Moose Brook 1 and Moose Brook 2..................................................................24 3.3h Bither Brook 3...................................................................................................24 4.0 CONCLUSIONS.........................................................................................................24 5.0 REFERENCES...........................................................................................................25 FIGURES………………………………………………………………………………...28 TABLES…………………………………………………………………………………45 APPENDICES…………………………………………………………………………...50 Fluvial geomorphology and culvert assessment of the Meduxnekeag River watershed - July 2010 Page 3 of 154 List of Figures Figure 1: Watershed map of Meduxnekeag River in Maine showing major tributaries. Figure 2: The Meduxnekeag River flows very muddy during runoff events. Figure 3: Extensive wetlands are a common feature on many of the tributaries to the Meduxnekeag River such as Pearce Brook. Figure 4: Topographic map of the Meduxnekeag River downstream of Houlton showing narrow valley through which the river flows. The river sometimes encounters the valley walls or valley constrictions. Figure 5: a) Sediment deposition directly into the Meduxnekeag River at the mouth of an unnamed tributary is b) enhanced by channel incision upstream caused by the concentration of flow after rebuilding of the Houlton Civic Center. Figure 6: Gravel bar on B Stream deposited upstream of a valley constriction. Figure 7: Artificial straightening probably occurred on lower Mill Brook where a straight channel is present along the valley margins despite an unconfined valley across which the channel could meander. Note presence of old meanders abandoned during the straightening. Figure 8: Dam across the Meduxnekeag River in Houlton. Photo date unknown. From Sleeper, 1994. Figure 9: Evidence for old dams no longer existing can be seen as a) large logs protruding from the bank and oriented normal to flow and b) fine-grained impoundment sediments often containing abundant logs and wood fragments. Figure 10: a) Historical photograph circa 1890 showing valley side slopes cleared of trees where b) today the forest cover has returned as seen on the 2003 orthophoto. Figure 11: a) Historical photograph circa 1890 of the Meduxnekeag River downstream of Cooks Brook contrasts dramatically with b) a recent photograph of the same area showing I-95 bridge crossing that spans almost the entire channel. Figure 12: Location of the geomorphic assessment sites. Figure 13: Flow complexity created by a) bedrock, b) isolated boulder, c) log jam, and d) boulder-supported log jam. Figure 14: a) Deep pool formed around boulder and b) sand and gravel deposited upstream of log jam Fluvial geomorphology and culvert assessment of the Meduxnekeag River watershed - July 2010 Page 4 of 154 Figure 15: High width:depth ratio channel at the Fish and Game Club site is shallow and slow moving at low flow. Figure 16: Riparian buffer planting projects will one day provide a supply of trees that will fall into the channel and increase flow complexity and habitat. Figure 17: Location of the culvert assessment sites. List of Tables Table 1: Length of channel features mapped along the Meduxnekeag River and ten tributaries. Table 2: Summary statistics for mapped channel features. Table 3: Morphological characteristics of the geomorphic assessment sites. Table 4: Morphological characteristics of the culvert assessment sites. List of Appendices Appendix 1: Historical topographic maps and aerial photographs. Appendix 2: GIS shapefiles of channel features mapping. Appendix 3: Topographic survey data for the geomorphic assessment sites. Appendix 4: Substrate particle size data for the geomorphic assessment sites. Appendix 5: Conceptual restoration designs for three geomorphic assessment sites. Appendix 6: Topographic survey data for the culvert assessment sites. Appendix 7: Substrate particle size data for the culvert assessment sites. Appendix 8: Conceptual habitat mitigation designs for the culvert assessment sites. Appendix 9: Ground photographs of the culvert assessment sites. Fluvial geomorphology and culvert assessment of the Meduxnekeag River watershed - July 2010 Page 5 of 154 EXECUTIVE SUMMARY A fluvial geomorphology and culvert assessment were conducted in the Meduxnekeag River watershed in Aroostook County, Maine to identify restoration projects that will assist the Houlton Band of Maliseet Indians fulfill their goal of sustaining tribal cultural practices along the river such as fishing. The fluvial geomorphology assessment identified watershed conditions and human activities influencing river morphology – the shape, sinuosity, and slope of the channel. The river flows through a narrow valley along most of its length (as do the lower tributaries), mostly as a consequence of the geological and glacial history of the region. Due to these natural constraints, the river channel is much straighter than a meandering stream on a wide floodplain. Similarly, the river channel has not experienced major shifts in position during the past 75 yrs. Flood flows concentrated in the narrow valley exert greater shear stress on the channel bed, a condition that leads to the development of a wide shallow channel if no roughness elements (i.e., boulders and logs) are present in the channel. Boulders and logs can reduce flow velocities, increase flow complexity, and encourage sediment deposition that all serve to narrow and deepen the channel. Historical evidence is unclear as to how much wood and boulder structure was present in the channel prior to European settlement of the region, but considerable amounts were probably removed during extensive logging and agricultural activities over the past two centuries. Reintroduction of this structure is the primary objective of three proposed restoration projects at the: 1) Lowery Bridge to the Covered Bridge site on the Meduxnekeag River, 2) Fish and Game Club site in Monticello upstream of the Route 1 Bridge on the North Branch, and 3) B Stream site upstream of the I-95 Bridge in Houlton. Boulder clusters, isolated logs, and boulder-supported log jams are examples of design measures that will not only improve habitat as isolated elements but can also function together to increase flow complexity, reduce the widths of the severely overwidened reaches, and maximize habitat improvements. All three types of structures proposed occur naturally in the watershed and are associated with excellent habitat features including deep pools for cover and clean gravels segregated from fines for spawning. The restoration proposals represent a passive approach to restoration that will be cheaper, more consistent with natural processes, and more sustainable than more active restoration approaches. The characterization of culvert impacts and identification of mitigation design measures to improve degraded habitat were the primary objectives of the culvert assessment. The morphology of the channels on either side of the ten culverts assessed reflects the culverts’ impact on sediment transport processes. Most culverts are less than half the width of the channel, causing fine sediment deposition upstream and deep scour pools and bank erosion downstream. As culverts are slated for replacement, the new culverts should span the bankfull width of the channel and incorporate floodplain culverts where floodplains are present. However, many of the problematic culverts were only recently replaced. Short-term design measures can be employed to mitigate the habitat impacts at the culverts long before culvert replacement will be possible (Appendix 8). Boulder weirs to reduce undermining of the culvert and log crib walls to prevent bank scouring are examples of design measures that can also enhance physical habitat conditions near the culverts. The results of the fluvial geomorphology and culvert assessment with a focus on both watershed-scale and local problems will be of assistance as the Houlton Band of the Maliseet Indians plan additional projects on the river intended to allow traditional tribal practices to continue long into the future. Fluvial geomorphology and culvert assessment of the Meduxnekeag River watershed - July 2010 Page 6 of 154 1.0 INTRODUCTION This report describes a fluvial geomorphology and culvert assessment completed by Field Geology Services in the Meduxnekeag River watershed of Aroostook County, Maine (Figure 1). From Meduxnekeag Lake, the Meduxnekeag River flows 23.1 miles to the Canadian border and drains a watershed area of 426 mi2 within Maine, including a portion of the North Branch watershed that ultimately joins the mainstem Meduxnekeag in Canada. The total watershed area at the river’s confluence with the St. John River in Canada is 516 mi2. The assessments reported on here do not include information on the river or surrounding watershed in Canada. A majority of the watershed is well forested but significant agricultural lands occur on the relatively flat uplands bordering the mainstem and the lower ends of major tributaries. Human development along the river is limited, although the river does flow through the city of Houlton as does the lower end of Pierce Brook, a significant tributary. The assessments were completed for the Houlton Band of Maliseet Indians who have a long cultural tradition of utilizing the river’s resources and have tribal lands in the watershed. Tribal culture is largely dependent upon the natural resources found in the waters, floodplains, and riparian zone of the Meduxnekeag River. The river is a critical link in preserving tribal practices, traditions, and history. The tribe’s goal in conducting the assessments is to identify and implement restoration opportunities in the Meduxnekeag Watershed that will improve and promote traditional uses of the river such as fishing. A preliminary habitat assessment of the Meduxnekeag River completed by the Maine Inland Fisheries and Wildlife identified a preponderance of wide and shallow channels that lacked high quality pools and large woody debris, conditions associated with warmer summer water temperatures and less channel complexity (Frost, 2002). High sediment loads during runoff events (Schalk and Tornes, 2005) are also of concern, because of their potential to degrade habitat and adversely effect water quality. Even relatively small runoff events can rapidly turn the usually clear water very muddy (Figure 2). The project reported on here consisted of a watershed-level fluvial geomorphology assessment and a detailed site-specific culvert assessment at ten tributary stream crossings with impaired habitat conditions. The geomorphology assessment had three primary objectives: 1) identify the natural conditions and human land use activities in the watershed that are potentially controlling channel morphology and ongoing fluvial processes; 2) determine how the channel has responded and continues to respond to these watershed conditions; and 3) select and prioritize restoration projects that will eliminate artificial constraints causing adverse channel responses and degraded aquatic habitat. The geomorphology assessment consisted of five work tasks designed to fulfill these objectives: 1) map and aerial photograph interpretation; 2) archival research; 3) mapping of channel features; 4) topographic surveying of channel dimensions; and 5) development of conceptual restoration designs for three priority sites. The results of each work task are described separately in Section 2.0 below. Fluvial geomorphology and culvert assessment of the Meduxnekeag River watershed - July 2010 Page 7 of 154 The results of the geomorphology assessment were in part used to identify the ten stream crossings to be assessed as part of the culvert assessment. The objectives of the culvert assessment were to: 1) conduct a detailed evaluation of ten priority culverts associated with degraded habitat and 2) create mitigation designs for the ten evaluated culverts. The culvert assessment consisted of three work tasks designed to fulfill these objectives: 1) topographic surveying of plan views, longitudinal profiles, and cross sections upstream and downstream of the culverts; 2) measurement of particle sizes (i.e., pebble counts) at the culverts; and 3) identification of design measures that will lead to improved habitat conditions. The results of each work task are described separately in Section 3.0 below. 2.0 FLUVIAL GEOMORPHOLOGY ASSESSMENT Fluvial geomorphology is a science devoted to understanding how the natural setting and human land use in a watershed determine the shape of the river channel. Fluvial geomorphology assessments seek to determine what physical changes are occurring to a stream channel in response to alterations in watershed conditions and, in turn, how these adjustments are impacting human infrastructure and fish habitat. A river's adjustment to watershed perturbations may take thousands of years, as is the case throughout much of New England in response to deglaciation. In other instances, channel modifications may occur in less than a decade, as is frequently the case with direct human activities in a stream channel. Understanding how these perturbations (i.e., changes), operating at different time scales, alter the width, depth, and planform of a channel is critical for identifying potential problem areas in a river system. Consequently, a geomorphology assessment can identify and prioritize restoration projects that can reduce erosion and flooding while improving aquatic habitat. 2.1 Map and aerial photograph interpretation 2.1a Watershed characterization The morphology of a river channel is a product of the natural conditions and human activities controlling the water, sediment, and wood inputs in the watershed. At least three characteristics of the Meduxnekeag Watershed increase the time required for runoff to reach the Canadian border and, therefore, reduce, but certainly not eliminate, the chance that extreme floods will inundate the channel and the associated physical habitat. First, the dendritic to rectilinear drainage pattern (Figure 1) means flow follows a longer path down the tributaries before reaching the river’s endpoint compared to a watershed with a radial drainage pattern where individual tributaries follow a more direct path to the outlet. In watersheds with a radial drainage pattern, runoff from all of the tributaries can reach the outlet at essentially the same time, leading to higher peak discharges. In a watershed like the Meduxnekeag, flow from various tributaries reach the river at different times, so peak flows are reduced but runoff continues for a longer period Fluvial geomorphology and culvert assessment of the Meduxnekeag River watershed - July 2010 Page 8 of 154 – an important factor for maintaining sufficient flow during the typically dryer summer months. A second characteristic increasing the runoff time to the river’s outlet is the presence of Meduxnekeag Lake and other wetlands in the watershed (Figure 1). The lake serves as a buffer between the upper watershed and the river such that large runoff events from the upper basin are stored within the lake (causing a relatively rapid rise in lake level) and drain into the river over a longer time period (causing a slower fall in lake level). Green Pond, a small body of water through which the river flows just downstream of the Mill Brook confluence (Figure 1), has a similar but, given its smaller size, a less significant effect than Meduxnekeag Lake. Runoff from tributary streams is slowed by the presence of extensive wetlands along their length (Figure 3), the result of the glacial topography of the region and greatly enhanced by beaver activity and natural log jams. Finally, the Meduxnekeag Watershed has a total relief of only 1,348 ft between Sam Drew Mountain and the downstream end of the mainstem at the Canadian border. On the North Branch, the relief between Number Nine Mountain and the Canadian border is slightly greater at 1,394 ft. In general, however, the relief is less than 500 ft over most of the watershed (Schalk and Tornes, 2005). Consequently, runoff likely moves through the basin much slower than similar sized watersheds in steeper more mountainous terrain. The USGS stream gauge data are consistent with the expectation that flows are not flashy and extreme peak flood events are less likely to occur in the Meduxnekeag Watershed, because the record peak flows recorded at the Houlton gauge are less than two times the average annual peak (see ). http://waterdata.usgs.gov/me/nwis/rt Once runoff from the Meduxnekeag Watershed reaches the river, the narrow valley through which much of the river flows has the potential to amplify river stage and promote rapid sediment deposition; both factors can potentially alter channel morphology and physical habitat dramatically. First, much of the river flows within a very narrow valley with no or very limited floodplain flanking the channel (Figure 4). Confined by the high valley walls, flood flows on the Meduxnekeag River move faster and flow at a greater depth for the same discharge compared to rivers with a wide floodplain. Given the narrow valley, the river impinges directly on the high banks of the valley wall at several locations (Figure 4), encountering both bedrock where deep pools can form and glacial deposits that can supply large amounts of fine sediment to the river in the event of a landslide. Another potential point source of sediments is from tributaries that flow directly into the river without a wide floodplain over which sediments can be stored, resulting in more direct impacts to channel morphology (Figure 5a). The problem can be made worse when land use activities in the tributary watershed are causing channel incision (Figure 5b). Within the valley, narrower constrictions occur that can have an important morphological impact on the channel due to their effect on the passage of flood flows (Figure 4). Flows are partially impounded behind the constrictions as the flow necks down to pass through the narrower area. This ponding or backwatering upstream of constrictions reduces flow velocities, leads to a reduction in the sediment transport capacity of the flow, and results in the deposition of large gravel bars (Figure 6). While the impacts of constrictions are most noticeable on tributaries such as B Stream, constrictions along the Meduxnekeag mainstem could also be altering physical habitat in Fluvial geomorphology and culvert assessment of the Meduxnekeag River watershed - July 2010 Page 9 of 154 more subtle ways such as enhancing fine sediment deposition that can fill pools and cover spawning gravels. The constrictions described above serve as grade controls, limiting the extent to which channel adjustments will travel upstream or downstream in response to natural events or human activities. For example a large landslide will typically result in the formation of gravel bars downstream in response to the increased sediment load, but a valley constriction will buffer downstream reaches from the effects of the landslide since most of the excess sediment will be accommodated immediately upstream of the constriction within the backwater zone. Lakes such as Green Pond, the large wetlands found on tributary streams, and dams (essentially artificial valley constrictions) also act as grade controls such that even significant perturbations in the upper watershed, whether natural or human caused, exert little direct influence on channel morphology compared to changes occurring more locally. Consequently, when trying to unravel the causes for channel adjustments that have degraded aquatic habitat in a given reach, focus should be placed on conditions and past events within the zone of influence of that river reach (i.e., the stretch of river and associated watershed between an upstream and downstream grade control). Human activities can also have a great impact on runoff characteristics and channel morphology. Nearly all rivers and streams in New England continue to adjust to artificial channel straightening, a common practice in the 19th and 20th centuries for improving agricultural lands, reducing flooding, and, perhaps most extensively, for easing the passage of logs downstream during annual log drives. By cutting off meanders and shortening the length of the stream, channel straightening increases the stream gradient. In response to the resulting increased stream power of floods, straightened channels undergo a period of incision and widening to return stream power back to its original pre-straightening level. However, the reconfigured, much wider, channel without meanders is associated with poorer quality habitat compared to a natural unaltered channel. The wide channels, with any sand and gravel bars removed by the incision and pools infilled, ensure summer flows are shallow and warm up more readily. The lack of meanders reduces flow complexity that is needed to carve deeper pools (i.e., create cover habitat) and segregate particles of different sizes (i.e., form clean spawning gravels). The amount of artificial straightening that occurred on the Meduxnekeag River and its tributaries is unclear given the limited space available within the narrow valley for well developed meanders to occur naturally. In other words, the lack of extensive meandering seen on the mainstem today (Figure 4) may be more a consequence of its natural confinement to a narrow valley rather than artificial straightening. Topographic evidence suggests some of the tributaries were straightened where valley confinement is not present (Figure 7). Although valley confinement probably reduced the amount of channel straightening that would have otherwise taken place, other activities associated with straightening, such as the removal of wood and boulders from the channel, probably did occur and would have had similar morphological and habitat impacts. Other human activities in the watershed with an influence on runoff and channel morphology, such as land clearance and dams, are discussed below in Section 2.1b. Fluvial geomorphology and culvert assessment of the Meduxnekeag River watershed - July 2010 Page 10 of 154 2.1b Historical changes Historical aerial photographs and topographic maps can be an important tool for studying changes in channel morphology and watershed land use. A 1934 topographic map and 1947 aerial photographs of the Meduxnekeag River were visually compared with the 2009 orthophotos to identify changes in land use and channel position (Appendix 1). Land use in the watershed has remained relatively unchanged since 1947 with the upper watersheds forested and the upland areas along the margins of the Meduxnekeag River valley heavily agricultural. Forests cover 79 percent of the watershed, agricultural lands occupy 17 percent, and urban areas and open water covering the remaining 4 percent (Southern Aroostook County Soil and Water Conservation District, 1993). The upper watershed is an active forest, so despite an overall small increase in forest cover at the watershed scale, localized areas have seen a dramatic loss in forest cover due to logging. These decreases in forest cover can degrade habitat in nearby tributaries by increasing peak flows and fine sediment inputs, while elevated summer low flow water temperatures can result from decreasing base flows. However, at the watershed scale, the marginal increases in forest cover in the upper Meduxnekeag Watershed since 1947 have potentially had a positive, albeit small, effect on aquatic habitat. Lower in the watershed, increased development in Houlton occurred north of I- 95, an interstate highway constructed after 1947. Also associated with the highway construction are new bridge crossings over tributaries and the mainstem. These changes in land use near Houlton, while noticeable, likely have little effect on the mainstem, because the changes occur over such a small percentage of the total watershed area. Recent development and runoff increases are more likely to have an impact on small tributaries such as occurred with the reconstruction of the Houlton Civic Center (Figure 5). Agricultural lands are prevalent on upland areas at the margins of the narrow Meduxnekeag River valley and lower ends of major tributaries. Runoff from the agricultural fields can increase fine sediment inputs to the mainstem, especially where the lower tributaries have a poor riparian buffer or lack other features (e.g., wetlands) that enhance sediment storage. Because of the potential for tributaries to buffer the river against upland land use changes, human activities occurring directly in the river channel are more likely to engender channel adjustments and changes to channel morphology. The most striking change on the Meduxnekeag mainstem since 1947 is the removal of the large dam on the river in Houlton, once a prominent feature in downtown (Figure 8). Significant changes in channel position have not occurred on the mainstem since 1934, not necessarily surprising given the narrow valley through which the river flows. Minor changes on the mainstem may have occurred, but are difficult to discern given the resolution of the historical images. Similarly, the small size of the tributaries makes identifying changes difficult, especially where riparian trees obscure the channel. Large-scale changes on the tributaries would be discernable, so the absence of such changes indicates the tributary channels have experienced only minor, if any, channel migration since 1934.