3.0 Port Elmsley Catchment: Riparian Conditions
The Stream Characterization Program evaluated 6.0 km of the Tay River in 2017 in the Port Elmsley catchment. A total of 60 stream survey assessments were completed in July. The Tay River watershed experienced high water levels along the Tay River and its tributaries in 2017. After moving from two years of drought conditions in 2015 and 2016 heavy rains throughout the year made 2017 the wettest year in recorded history. Flows out of Perth and downstream to Lower Rideau Lake, as with the rest of the Tay River watershed remained relatively high through 2017 in reaction to the wet weather. Some property flooding occurred between Beveridges Dam and Port Elsmley with the highest flows in May. No residential flooding was reported but shoreline erosion was an issue.
High flows along the Tay River at the Port Elmsley Road in the spring of 2017
3.1 Tay River Overbank Zone
3.1.1 Riparian Buffer Evaluation
The quality of the riparian area increases with the width, complexity and linear extent of its vegetation along a stream or creek. A complex riparian community consists of diverse plant species native to the site, with multiple age-classes providing vertical structural diversity along a watercourse.
Here is a list of watershed benefits from a healthy riparian buffer zone:
- Reduces the amount of pollutants that reach the stream from surface runoff
- Helps reduce and mitigates erosion
- Provides a microclimate that is cooler during the summer months providing cooler water for aquatic organisms
- Provides large wood structure from fallen trees and limbs that form instream cover, create pools, stabilize the streambed, and provide habitat for aquatic organisms
- Provides organic material for stream biota that, among other functions, is the base of the food chain in lower order streams
- Provides habitat for terrestrial insects that drop in the stream and become food for fish and travel corridors for other terrestrial animals
- Dissipates energy during flood events
- Often provides the only refuge areas for fish during out-of-bank flows (behind trees, stumps, and logs)
Figure 9 demonstrates the buffer conditions of the left and right banks separately. The Tay River had a buffer of greater than 30 meters along 88 percent of the left bank and 66 percent of the right bank.
Figure 9 Riparian Buffer Evaluation along the Tay River in the Port Elmsley catchment
3.1.2 Riparian Buffer Alterations
Alterations within the riparian buffer were assessed within three distinct shoreline zones (0-5m, 5-15m, 15-30m), and evaluated based on the dominant vegetative community and/or land cover type (Figure 10). The riparian buffer zone along the Tay River was found to be dominated by forest, scrubland, wetland and meadow conditions.
Figure 10 Riparian buffer alterations along the Tay River in the Port Elmsley catchment
3.1.3 Adjacent Land Use
The RVCA’s Stream Characterization Program identifies eight different land uses along the Tay River (Figure 11). Surrounding land use is considered from the beginning to end of the survey section (100m) and up to 100m on each side of the river. Land use outside of this area is not considered for the surveys but is nonetheless part of the subwatershed and will influence the creek. Forest habitat was dominant at 98 percent; scrubland was found along 75 percent of the surveyed sections, wetland habitat was observed along 62 percent of the system and 23 percent meadow habitat was present along the Tay River. The remaining land use consisted of residential, pasture, recreational and infrastructure in the form of road crossings.
Figure 11 Land Use along the Tay River in the Port Elmsley catchment
3.2 Tay River Shoreline Zone
3.2.1 Instream Erosion
Stream erosion is the process by which water erodes and transports sediments, resulting in dynamic flows and diverse habitat conditions. Excessive erosion can result in drastic environmental changes, as habitat conditions, water quality and aquatic life are all negatively affected. Bank stability was assessed as the overall extent of each section with “unstable” shoreline conditions. These conditions are defined by the presence of significant exposed soils/roots, minimal bank vegetation, severe undercutting, slumping or scour and potential failed erosion measures. The Tay River had no erosion observed along the majority of surveyed sections with a few sections having low to moderate levels of erosion (Figure 12).
Figure 12 Erosion levels along the Tay River in the Port Elmsley catchment
3.2.2 Undercut Stream Banks
Stream bank undercuts can provide excellent cover habitat for aquatic life, however excessive levels can be an indication of unstable shoreline conditions. Bank undercut was assessed as the overall extent of each surveyed section with overhanging bank cover present. Figure 13 shows that the Tay River had no observed undercut banks along the majority of the system, however there were several sections in the upper reaches with high to moderate levels of undercut banks.
Figure 13 Undercut stream banks along the Tay River in the Port Elmsley catchment
3.2.3 Stream Shading
Grasses, shrubs and trees all contribute towards shading a stream. Shade is important in moderating stream temperature, contributing to food supply and helping with nutrient reduction within a stream. Stream cover is assessed as the total coverage area in each section that is shaded by overhanging trees/grasses and tree canopy, at greater than 1m above the water surface. Figure 14 shows low levels of stream shading along the majority of the Tay River.
Figure 14 Stream shading along the Tay River in the Port Elmsley catchment
3.2.4 Instream Wood Structure
Forested shorelines provide essential complex habitat through the perpetual process of shoreline trees falling into the water. This continuous recruitment of trees creates a wood-based physical structure in the littoral zone that is common on natural systems. Insects, fish, amphibians, birds, and other animals have also evolved with this abundance of near shore wood and it is essential to their life cycles. With increased development along many waterways, forested lakeshores have been altered and wood-based physical structure in many waterways has been reduced. It is important to restore this essential habitat to aquatic ecosystems.
- Protects shorelines by providing a barrier from wind and wave erosion
- Reduces sedimentation of the water caused by shoreline slumping due to bank erosion
- Allows detritus to collect and settle on the lake or creek bed providing the substrate structure required for native aquatic vegetation to establish and outcompete invasive species
- Wood complexes are an important food source for invertebrates
- Small fish feed on the abundance of invertebrates that are found around these structures
- Larger fish, waterfowl and shorebirds all benefit from the abundance of invertebrates and small fish feeding around woody structures in the littoral zone
- Cover from predators is essential for many fish and animals to successfully complete their life cycle
- The nooks and crannies of wood complexes offer critters safety from predators while at the same time concentrating prey to make predators more efficient
- Wood provides the structure on which many species must lay or attach their eggs, therefore these complexes provide quality spawning and nesting habitat
- Wood complexes in the littoral zone provide unique edge habitat along the shoreline
- Edge habitats contain more species diversity and higher concentrations of species than the adjoining habitats themselves will have
Figure 15 shows that the majority of the Tay River had low levels of instream wood structure along the system. There were several stream survey sections which were characterized as having moderate levels of instream wood structure in the form of branches and trees.
Figure 15 Instream wood structure along the Tay River in the Port Elmsley catchment
3.2.5 Overhanging Wood Structure
Trees and branches that are less than one meter from the surface of the water are defined as overhanging. Overhanging branches and trees provide a food source, nutrients and shade which helps to moderate instream water temperatures. Figure 16 shows the system is somewhat variable with no overhanging branches and trees where the river is wide and is dominated by wetland habitat to areas that have moderate levels of overhanging wood structure along the Tay River.
Figure 16 Overhanging wood structure along the Tay River in the Port Elmsley catchment
3.2.6 Anthropogenic Alterations
Stream alterations are classified based on specific functional criteria associated with the flow conditions, the riparian buffer and potential human influences. Figure 17 shows twenty seven percent of the Tay River remains “unaltered” with no anthropogenic alterations. Sixty eight percent of the Tay River was classified as natural with minor anthropogenic changes. Five percent of sections were considered altered; while no sections were classified as highly altered. The alterations along the Tay River were in the form of shoreline modifications and road crossings.
Figure 17 Anthropogenic alterations along the Tay River in the Port Elmsley catchment
3.3 Tay River Instream Aquatic Habitat
3.3.1 Benthic Invertebrates
Freshwater benthic invertebrates are animals without backbones that live on the stream bottom and include crustaceans such as crayfish, molluscs and immature forms of aquatic insects. Benthos represent an extremely diverse group of aquatic animals and exhibit wide ranges of responses to stressors such as organic pollutants, sediments and toxicants, which allows scientists to use them as bioindicators. As part of the Ontario Benthic Biomonitoring Network (OBBN), the RVCA has been collecting benthic invertebrates at the Port Elmsley Road site since 2003. Monitoring data is analyzed for each sample site and the results are presented using the Family Biotic Index, Family Richness and percent Ephemeroptera, Plecoptera and Trichoptera.
OBBN sample location at the Port Elmsley Road
Hilsenhoff Family Biotic Index
The Hilsenhoff Family Biotic Index (FBI) is an indicator of organic and nutrient pollution and provides an estimate of water quality conditions for each site using established pollution tolerance values for benthic invertebrates. FBI results for the Port Elmsley - Tay River catchment at the Port Elmsley Road sample location is summarized by year. “Good” to “Poor” water quality conditions were observed at the Tay River sample location (Figure 18) using a grading scheme developed by Conservation Authorities in Ontario for benthic invertebrates.
Figure 18 Hilsenhoff Family Biotic Index at the Port Elmsley Road sample location
Family Richness measures the health of the community through its diversity and increases with increasing habitat diversity suitability and healthy water quality conditions. Family Richness is equivalent to the total number of benthic invertebrate families found within a sample. The Port Elmsley Road location is reported to have “Good” family richness (Figure 19).
Figure 19 Family Richness at the Port Elmsley Road sample location
Ephemeroptera (Mayflies), Plecoptera (Stoneflies), and Trichoptera (Caddisflies) are species considered to be very sensitive to poor water quality conditions. High abundance of these organisms is generally an indication of good water quality conditions at a sample location. There appears to be a difference in community composition between the spring and fall results for the Port Elmsley Road site. The community structure is typically dominated by species that are sensitive to poor water quality conditions in the fall, while the spring results have more of a mixed community of species that are more tolerant to poorer water quality conditions. As a result, the EPT indicates that the Port Elmsley Road sample location is reported to have “Good” to “Fair” water quality (Figure 20) during the reporting periods.
Figure 20 EPT on the Tay River at the Port Elmsley Road sample location
Overall the Tay River site in the Port Elmsley catchment from a benthic invertebrate perspective is considered “Fair” as the samples shift in community composition from species that are sensitive to high organic pollution levels in the fall to more tolerant species in the spring.
3.3.2 Habitat Complexity
Habitat complexity is a measure of the overall diversity of habitat types and features within a stream. Streams with high habitat complexity support a greater variety of species niches, and therefore contribute to greater diversity. Factors such as substrate, flow conditions (pools, riffles) and cover material (vegetation, wood structure, etc.) all provide crucial habitat to aquatic life. Habitat complexity is assessed based on the presence of boulder, cobble and gravel substrates, as well as the presence of instream wood structure.
No to high habitat complexity was identified for the Tay River in the Port Elmsley catchment (Figure 21). Regions with increased habitat complexity were observed throughout most of the reaches of the Tay River within the catchment.
Figure 21 Habitat complexity along the Tay River in the Port Elmsley catchment
3.3.3 Instream Substrate
Diverse substrate is important for fish and benthic invertebrate habitat because some species have specific substrate requirements and for example will only reproduce on certain types of substrate. The absence of diverse substrate types may limit the overall diversity of species within a stream. Substrate conditions were highly diverse along the Tay River (Figure 22) with all substrate types being recorded at various locations along the system. Figure 23 shows the dominant substrate type observed for each section surveyed along the Tay River.
Figure 22 Instream substrate along the Tay River in the Port Elmsley catchment
Figure 23 shows the dominant substrate type along the Tay River in the Port Elmsley catchment
3.3.4 Instream Morphology
Pools and riffles are important habitat features for aquatic life. Riffles are fast flowing areas characterized by agitation and overturn of the water surface. Riffles thereby play a crucial role in contributing to dissolved oxygen conditions and directly support spawning for some fish species. They are also areas that support high benthic invertebrate populations which are an important food source for many aquatic species. Pools are characterized by minimal flows, with relatively deep water and winter/summer refuge habitat for aquatic species. Runs are moderately shallow, with unagitated surfaces of water and areas where the thalweg (deepest part of the channel) is in the center of the channel. Figure 24 shows that the Tay River is highly variable; 98 percent of sections recorded runs, 72 percent pools and 28 percent riffles. Figure 25 shows the riffle habitat areas were observed primarily in the lower reach of the Tay River.
Figure 24 Instream morphology along the Tay River in the Port Elmsley catchment
Figure 25 Instream riffle habitat along the Tay River in the Port Elmsley catchment
3.3.5 Vegetation Type
Instream vegetation provides a variety of functions and is a critical component of the aquatic ecosystem. Aquatic plants promote stream health by:
- Providing direct riparian/instream habitat
- Stabilizing flows reducing shoreline erosion
- Contributing to dissolved oxygen through photosynthesis
- Maintaining temperature conditions through shading
For example emergent plants along the shoreline can provide shoreline protection from wave action and important rearing habitat for species of waterfowl. Submerged plants provide habitat for fish to find shelter from predator fish while they feed. Floating plants such as water lilies shade the water and can keep temperatures cool while reducing algae growth. Submerged plants were observed in 90 percent of sections, narrow leaved emergents in 87 percent of sections, robust emergents present in 62 percent of the survey sections, 77 percent of sections contained algae, 50 percent floating plants, 20 percent free floating, 60 percent broad leaved emergents and 77 percent of sections had areas with no instream vegetation and were primarily located in areas with bedrock substrate. Figure 26 depicts the plant community structure for the Tay River. Figure 27 shows the dominant vegetation type observed for each section surveyed along the Tay River in the Port Elmsley catchment.
Figure 26 Vegetation type along the Tay River in the Port Elmsley catchment
Figure 27 Dominant vegetation type along the Tay River in the Port Elmsley catchment
3.3.6 Instream Vegetation Abundance
Instream vegetation is an important factor for a healthy stream ecosystem. Vegetation helps to remove contaminants from the water, contributes oxygen to the stream, and provides habitat for fish and wildlife. Too much vegetation can also be detrimental. Figure 28 demonstrates that the Tay River had normal to common levels of vegetation recorded at 67 and 63 percent of stream surveys. Extensive levels of vegetation were observed in 17 percent of the surveyed sections and were consistent with areas dominated by the invasive aquatic plant known as European frogbit; while eighteen percent of sections had no vegetation in areas.
Figure 28 Instream vegetation abundance along the Tay River in the Port Elmsley catchment
3.3.7 Invasive Species
Invasive species can have major implications on streams and species diversity. Invasive species are one of the largest threats to ecosystems throughout Ontario and can out compete native species, having negative effects on local wildlife, fish and plant populations. Seventy five percent of the sections surveyed along the Tay River in the Port Elmsley catchment had invasive species. The invasive species observed were European frogbit, Eurasian milfoil, banded mystery snail, purple loosestrife, honeysuckle, wild parsnip, Manitoba maple, curly leafed pondweed and common/glossy buckthorn. Invasive species abundance (i.e. the number of observed invasive species per section) was assessed to determine the potential range/vector of many of these species (Figure 29).
Figure 29 Invasive species abundance along the Tay River in the Port Elmsley catchment
3.3.8 Water Chemistry
During the stream characterization survey, a YSI probe is used to collect water chemistry information. Dissolved oxygen (DO), specific conductivity (SPC) and pH are measured at the start and end of each section.
220.127.116.11 Dissolved Oxygen
Dissolved oxygen is a measure of the amount of oxygen dissolved in water. The Canadian Environmental Quality Guidelines of the Canadian Council of Ministers of the Environment (CCME) suggest that for the protection of aquatic life the lowest acceptable dissolved oxygen concentration should be 6 mg/L for warmwater biota and 9.5 mg/L for coldwater biota (CCME, 1999). Figure 30 shows that the dissolved oxygen in Tay River supports warmwater and coolwater biota along the system. The average dissolved oxygen level observed within Port Elmsley catchment was 7.7mg/L which meets the recommended level for warm and cool water biota.
Figure 30 Dissolved oxygen ranges along the Tay River in the Port Elmsley catchment
Conductivity in streams is primarily influenced by the geology of the surrounding environment, but can vary drastically as a function of surface water runoff. Currently there are no CCME guideline standards for stream conductivity; however readings which are outside the normal range observed within the system are often an indication of unmitigated discharge and/or stormwater input. The average conductivity observed within the Tay River was 202.5 µs/cm. Figure 31 shows the conductivity readings for the Tay River in the Port Elmsley catchment.
Figure 31 Specific conductivity ranges in the Tay River in the Port Elmsley catchment
Based on the PWQO for pH, a range of 6.5 to 8.5 should be maintained for the protection of aquatic life. Average pH values along the Tay River were 7.64 thereby meeting the provincial standard (Figure 32).
Figure 32 pH ranges along the Tay River in the Port Elmsley catchment
18.104.22.168 Oxygen Saturation (%)
Oxygen saturation is measured as the ratio of dissolved oxygen relative to the maximum amount of oxygen that will dissolve based on the temperature and atmospheric pressure. Well oxygenated water will stabilize at or above 100% saturation, however the presence of decaying matter/pollutants can drastically reduce these levels. Oxygen input through photosynthesis has the potential to increase saturation above 100% to a maximum of 500%, depending on the productivity level of the environment. In order to represent the relationship between concentration and saturation, the measured values have been summarized into 6 classes:
Dissolved oxygen conditions for the Tay River varied along the system for both warm and coolwater species (Figure 33). Certain sections in the lower reach were above the guideline to support coldwater biota.
Figure 33 A bivariate assessment of dissolved oxygen concentration (mg/L) and saturation (%) along the Tay River in the Port Elmsley catchment
22.214.171.124 Specific Conductivity Assessment
Specific conductivity (SPC) is a standardized measure of electrical conductance, collected at or corrected to a water temperature of 25⁰C. SPC is directly related to the concentration of ions in water, and is commonly influenced by the presence of dissolved salts, alkalis, chlorides, sulfides and carbonate compounds. The higher the concentration of these compounds, the higher the conductivity. Common sources of elevated conductivity include storm water, agricultural inputs and commercial/industrial effluents.
In order to summarize the conditions observed, SPC levels were evaluated as either normal, moderately elevated or highly elevated. These categories correspond directly to the degree of variation (i.e. standard deviation) at each site relative to the average across the system.
Normal levels were maintained in the middle reaches of the Tay River, however there were moderately elevated areas in the upper and lower reaches (Figure 34).
Figure 34 Relative specific conductivity levels along the Tay River in the Port Elmsley catchment
3.3.9 Thermal Regime
Many factors can influence fluctuations in stream temperature, including springs, tributaries, precipitation runoff, discharge pipes and stream shading from riparian vegetation. Water temperature is used along with the maximum air temperature (using the Stoneman and Jones method) to classify a watercourse as either warm water, cool water or cold water. Figure 35 shows where the thermal sampling sites were located on the Tay River in the Port Elmsley catchment. Analysis of the data collected indicates that the Tay River is classified as a warm water system (Figure 36).
Figure 35 Temperature logger locations along the Tay River in the Port Elmsley catchment
Figure 36 Temperature logger data for the sites along the Tay River in the Port Elmsley catchment
Each point on the graph represents a temperature that meets the following criteria:
- Sampling dates between July 1st and September 7th
- Sampling date is preceded by two consecutive days above 24.5 °C, with no rain
- Water temperatures are collected at 4pm
- Air temperature is recorded as the max temperature for that day
Groundwater discharge areas can influence stream temperature, contribute nutrients, and provide important stream habitat for fish and other biota. During stream surveys, indicators of groundwater discharge are noted when observed. Indicators include: springs/seeps, watercress, iron staining, significant temperature change and rainbow mineral film. Figure 37 shows areas where one or more of the above groundwater indicators were observed during stream surveys and headwater assessments.
Figure 37 Groundwater indicators observed in the Port Elmsley catchment
3.3.11 Fish Community
The Port Elmsley catchment is classified as a mixed community of warm and cool water recreational and baitfish fishery with 19 species observed. Figure 38 shows the historical and 2017 fish sampling locations in the catchment.
Figure 38 Tay River Port Elmsley catchment fish community
Table 6 lists the species observed in the watershed historically and during the 2017 sampling effort.
Fish species observed in the Port Elmsley catchment
Fish being identified, weighed and measured while sampling in the Port Elmsley catchment
3.3.12 Migratory Obstructions
It is important to know locations of migratory obstructions because these can prevent fish from accessing important spawning and rearing habitat. Migratory obstructions can be natural or manmade, and they can be permanent or seasonal. Figure 39 shows that Port Elmsley catchment had one dam on the Tay River.
Figure 39 Migratory obstructions in the Port Elmsley catchment
The Beveridges Dam as seen by an RVCA field crew while conducting the 2017 stream survey of the Tay River
3.4 Headwater Drainage Feature Assessment
3.4.1 Headwaters Sampling Locations
The RVCA Stream Characterization program assessed Headwater Drainage Features for the Port Elmsley catchment in 2016. This protocol measures zero, first and second order headwater drainage features (HDF). It is a rapid assessment method characterizing the amount of water, sediment transport, and storage capacity within headwater drainage features (HDF). RVCA is working with other Conservation Authorities and the Ministry of Natural Resources and Forestry to implement the protocol with the goal of providing standard datasets to support science development and monitoring of headwater drainage features. An HDF is a depression in the land that conveys surface flow. Additionally, this module provides a means of characterizing the connectivity, form and unique features associated with each HDF (OSAP Protocol, 2013). In 2017 the program sampled 19 sites at road crossings in the Port Elmsley catchment area (Figure 40).
Figure 40 Location of the headwater sampling sites in the Port Elmsley catchment
3.4.2 Headwater Feature Type
The headwater sampling protocol assesses the feature type in order to understand the function of each feature. The evaluation includes the following classifications: defined natural channel, channelized or constrained, multi-thread, no defined feature, tiled, wetland, swale, roadside ditch and pond outlet. By assessing the values associated with the headwater drainage features in the catchment area we can understand the ecosystem services that they provide to the watershed in the form of hydrology, sediment transport, and aquatic and terrestrial functions. The headwater drainage features in the Port Elmsley catchment are highly variable features. Figure 41 shows the feature type of the primary feature at the sampling locations.
Figure 41 Headwater feature types in the Port Elmsley catchment
3.4.3 Headwater Feature Flow
The observed flow condition within headwater drainage features can be highly variable depending on timing relative to the spring freshet, recent rainfall, soil moisture, etc. Flow conditions are assessed in the spring and in the summer to determine if features are perennial and flow year round, if they are intermittent and dry up during the summer months or if they are ephemeral systems that do not flow regularly and generally respond to specific rainstorm events or snowmelt. Flow conditions in headwater systems can change from year to year depending on local precipitation patterns. Figure 42 shows the observed flow condition at the sampling locations in the Port Elmsley catchment.
Figure 42 Headwater feature flow conditions in the Port Elmsley catchment
A spring photo of the headwater sample site in the Port Elmsley catchment located on Drummond Concession 2
A summer photo of the headwater sample site in the Port Elmsley catchment located on Drummond Concession 2
3.4.4 Feature Channel Modifications
Channel modifications were assessed at each headwater drainage feature sampling location. Modifications include channelization, dredging, hardening and realignments. The Port Elmsley catchment area had a majority of features with no channel modifications observed, six sites as having been historically dredged/channelized and one location had mixed modifications. Figure 43 shows the channel modifications observed at the sampling locations for Port Elmsley catchment.
Figure 43 Headwater feature channel modifications in the Port Elmsley catchment
3.4.5 Headwater Feature Vegetation
Headwater feature vegetation evaluates the type of vegetation that is found within the drainage feature. The type of vegetated within the channel influences the aquatic and terrestrial ecosystem values that the feature provides. For some types of headwater features the vegetation within the feature plays a very important role in flow and sediment movement and provides wildlife habitat. The following classifications are evaluated no vegetation, lawn, wetland, meadow, scrubland and forest. Figure 44 depicts the dominant vegetation observed at the sampled headwater sites in the Port Elmsley catchment.
Figure 44 Headwater feature vegetation types in the Port Elmsley catchment
3.4.6 Headwater Feature Riparian Vegetation
Headwater riparian vegetation evaluates the type of vegetation that is found along the adjacent lands of a headwater drainage feature. The type of vegetation within the riparian corridor influences the aquatic and terrestrial ecosystem values that the feature provides to the watershed. Figure 45 depicts the type of riparian vegetation observed at the sampled headwater sites in the Port Elmsley catchment.
Figure 45 Headwater feature riparian vegetation types in the Port Elmsley catchment
3.4.7 Headwater Feature Sediment Deposition
Assessing the amount of recent sediment deposited in a channel provides an index of the degree to which the feature could be transporting sediment to downstream reaches (OSAP, 2013). Evidence of excessive sediment deposition might indicate the requirement to follow up with more detailed targeted assessments upstream of the site location to identify potential best management practices to be implemented. Sediment deposition ranged from none to substantial for the headwater sites sampled in the Port Elmsley catchment area. Figure 46 depicts the degree of sediment deposition observed at the sampled headwater sites in the Port Elmsley catchment. Sediment deposition conditions ranged from no sediment deposition to substantial.
Figure 46 Headwater feature sediment deposition in the Port Elmsley catchment
3.4.8 Headwater Feature Upstream Roughness
Feature roughness will provide a measure of the amount of materials within the bankfull channel that could slow down the velocity of water flowing within the headwater feature (OSAP, 2013). Materials on the channel bottom that provide roughness include vegetation, woody Structure and boulders/cobble substrates. Roughness can provide benefits in mitigating downstream erosion on the headwater drainage feature and the receiving watercourse by reducing velocities. Roughness also provides important habitat conditions for aquatic organisms. Figure 47 shows the feature roughness conditions at the sampling locations in the Port Elmsley catchment were highly variable ranging from minimal to extreme.
Figure 47 Headwater feature roughness in the Port Elmsley catchment