3.0 Glen Tay Catchment: Riparian Conditions
The Stream Characterization Program evaluated 17.9 km of the Tay River and the Scotts Snye in 2017 in the Glen Tay catchment. A total of 135 stream surveys on the Tay River and 44 on the Scotts Snye were completed in the June and July. For the purposes of the report the results for both systems are summarized together.
In 2017 the Tay River subwatershed experienced high water levels along the Tay River and its tributaries. In addition many of the Tay watershed lakes also experienced prolonged high water levels including Christie Lake immediately upstream of this reach. 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. The high flows out of Bobs Lake and through Christie Lake caused some out of bank flooding downstream of Althorpe Road affecting properties on Bathurst Concession 2 and Noonan Sideroad. No other flooding was recorded which would be because of the topography – relatively flat from Christie Lake through Althorpe Road to Noonan Sideroad with slower flows and low banks. Below Noonan Road, the gradient increases and the water moves more quickly downstream and does not overtop the banks as easily. Flows remained above average through the year with the frequent rain events.
3.1 Glen Tay - Tay River Overbank Zone
3.1.1 Riparian Land Cover 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 and the Scotts Snye had a buffer of greater than 30 meters along 90 percent of the left bank and 88 percent of the right bank.
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 and the Scotts Snye was found to be dominated by forest, scrubland, wetlands and meadow conditions. There were minimal areas with altered riparian zone conditions along the majority of the system.
3.1.3 Adjacent Land Use
The RVCA’s Stream Characterization Program identifies eleven different land uses along the Tay River and the Scotts Snye (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 93 percent; scrubland was found along 70 percent of the surveyed sections, wetland habitat was observed along 45 percent of the system and 15 percent meadow habitat was present along the Tay River and Scotts Snye. The remaining land use consisted of residential, pasture, active/abandoned agriculture, recreational and infrastructure in the form of road crossings.
3.2 Glen Tay - 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 majority of the Tay River and the Scotts Snye had no erosion observed along the majority of surveyed sections with a few small sections having low levels of erosion (Figure 12).
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 and the Scotts Snye had no observed undercut banks along the majority of the system, however there were several short sections with low to moderate levels of undercut banks.
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 Tay River and the Scotts Snye. Stream shading conditions were highly variable along the Tay River and the Scotts Snye ranging from no overhead canopy cover to high levels.
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 and forested lakeshores having been altered as a result wood-based physical structure in many waterbodies 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 and the Scotts Snye had low levels of instream wood structure along the system. There were several stream survey sections in the middle reach which were characterized as having moderate to high levels of instream wood structure in the form of branches and trees along the system.
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 variable with no overhanging branches and trees to areas that have high levels of overhanging wood structure along the Tay River and the Scotts Snye.
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 sixty six percent of the Tay River and the Scotts Snye remains “unaltered” with no anthropogenic alterations. Thirty one percent of the Tay River and the Scotts Snye was classified as natural with minor anthropogenic changes. Three percent of survey sections were classified as being altered they consisted of sections with road crossings and areas with shoreline modifications.
3.3 Glen Tay - Tay River Instream Aquatic Habitat
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 Bowes Side Road site since 2011. The site was added to the monitoring network as a result of an identified gap in the program during the first reporting cycle. 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.
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 Glen Tay - Tay River catchment at the Bowes Side Road sample location is summarized by year. “Good” to “Excellent” 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.
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 Tay River sample location is reported to have “Good” family richness (Figure 19).
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. The community structure is typically dominated by species that are sensitive to poor water quality conditions. As a result, the EPT indicates that Tay River sample location is reported to have “Good” water quality (Figure 20) during the reporting periods.
Overall the Tay River sample location in the Glen Tay catchment from a benthic invertebrate perspective is considered “Excellent” as the samples are dominated with species that are sensitive to high organic pollution levels.
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.
Moderate to high habitat complexity was identified for the Tay River and the Scotts Snye (Figure 21). Regions with increased habitat complexity were observed throughout the reaches of the system within the 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. Figure 22 shows the overall presence of various substrate types observed along Grants Creek. Substrate conditions were highly diverse along the Tay River and the Scotts Snye 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 and the Scotts Snye.
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 and the Scotts Snye are highly variable; 92 percent of sections recorded runs, 62 percent pools and 48 percent riffles. Figure 25 shows where the riffle habitat areas were observed along the Tay River and the Scotts Snye.
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. Narrow leaved emergents were observed in 86 percent of sections, submerged plants at 87 percent, 78 percent broad leaved emergents, 65 percent of sections contained algae, 64 percent floating plants, while robust emergents were present in 39 percent of the survey sections. Figure 26 depicts the plant community structure for the Tay River and the Scotts Snye. Figure 27 shows the dominant vegetation type observed for each section surveyed along the Tay River and the Scotts Snye in the Glen Tay 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 and the Scotts Snye had normal to common levels of vegetation recorded at 49 and 46 percent of stream surveys. Extensive levels of vegetation were observed in 28 percent of the surveyed sections, while 45 percent of sections had no vegetation in areas that were dominated by bedrock substrate conditions.
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. Ninety five percent of the sections surveyed along the Tay River and the Scotts Snye in the Glen Tay catchment had invasive species. The invasive species observed were European frogbit, banded mystery snail, Chinese mystery snail, curly leafed pondweed, dog strangling vine, Eurasian milfoil, European/Black alder, flowering rush, honey suckle, Manitoba maple, zebra mussel, yellow iris, poison/wild parsnip, purple loosestrife, bull thistle 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).
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 and the Scotts Snye supports warmwater and in certain locations coldwater biota along the system. The average dissolved oxygen level observed within the Glen Tay - Tay River catchment was 8.2mg/L which meets the recommended level for warm and cool water biota.
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 and the Scotts Snye was 145.8 µs/cm. Figure 31 shows the conductivity readings for the Tay River and the Scotts Snye in the Glen Tay 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 and the Scotts Snye were 7.83 thereby meeting the provincial standard (Figure 32).
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.
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 and the Scotts Snye, however there were moderately elevated areas in the middle and lower reaches (Figure 34). Two sections had high conductivity levels observed in the lower reach.
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 and the Scotts Snye in the Glen Tay catchment. Analysis of the data collected indicates that the Tay River and the Scotts Snye are classified as warm water systems (Figure 36).
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.
The Tay River and the Scotts Snye Glen Tay catchment is classified as a mixed community of warm and cool water recreational and baitfish fishery with 29 species observed (Figure 38). Table 6 displays a list of species observed in the watershed in 2017 and historically.
|Fish Species||Scientific Name||Fish code||Historical||2017|
|banded killifish||Fundulus diaphanus||BaKil||X||X|
|blackchin shiner||Notropis heterodon||BcShi||X|
|blacknose dace||Rhinichthys atratulus||BnDac||X|
|blacknose shiner||Notropis heterolepis||BnShi||X|
|bluntnose minnow||Pimephales notatus||BnMin||X||X|
|brook stickleback||Culaea inconstans||BrSti||X|
|brown bullhead||Ameiurus nebulosus||BrBul||X||X|
|carps and minnows||Cyprinidae||CA_MI||X|
|central mudminnow||Umbra limi||CeMud||X|
|central stoneroller||Campostoma anomalum||CeSto||X|
|common shiner||Luxilus cornutus||CoShi||X||X|
|creek chub||Semotilus atromaculatus||CrChu||X|
|emerald shiner||Notropis atherinoides||EmShi||X|
|etheostoma sp.||etheostoma sp.||EthSp||X|
|fathead minnow||Pimephales promelas||FhMin||X|
|hornyhead chub||Nocomis biguttatus||HhChu||X||X|
|iowa darter||Etheostoma exile||IoDar|
|johnny darter||Etheostoma nigrum||JoDar||X|
|largemouth bass||Micropterus salmoides||LmBas||X|
|longnose dace||Rhinichthys cataractae||LnDac||X|
|northern pearl dace||Margariscus nachtriebi||PeDac||X|
|northern pike||Esox lucius||NoPik||X||X|
|northern redbelly dace||Chrosomus eos||NRDac||X|
|rock bass||Ambloplites rupestris||RoBas||X||X|
|smallmouth bass||Micropterus dolomieu||SmBas||X||X|
|spottail shiner||Notropis hudsonius||StShi||X|
|white sucker||Catostomus commersonii||WhSuc||X|
|yellow bullhead||Ameiurus natalis||YeBul||X|
|yellow perch||Perca flavescens||YePer||X|
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 Glen Tay catchment had one perched culvert on a headwater drainage feature and one natural grade barrier on the Tay River.
3.3.13 Beaver Dams
Overall beaver dams create natural changes in the environment. Some of the benefits include providing habitat for wildlife, flood control, and silt retention. Additional benefits come from bacterial decomposition of woody material used in the dams which removes excess nutrient and toxins. Beaver dams can also result in flooding of agricultural lands and may be potential barriers to fish migration. Several beaver dams were identified along the Scotts Snye at the time of the survey (Figure 40).
3.3.14 Riparian Restoration
Figure 41 depicts the locations of riparian restoration opportunities as a result of observations made during the stream survey. Two riparian planting opportunities were identified on headwater drainage features in the Glen Tay catchment.
3.4.1 Headwaters Sampling Locations
The RVCA Stream Characterization program assessed Headwater Drainage Features for the Glen Tay - Tay River catchment in 2017. 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 Glen Tay catchment area (Figure 42).
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 Glen Tay catchment are highly variable. Figure 43 shows the feature type of the primary feature at the sampling locations.
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 44 shows the observed flow condition at the sampling locations in the Glen Tay catchment.
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 Glen Tay catchment area had a majority of features with no channel modifications observed, five sites as having been historically dredged/channelized and two locations had mixed modifications. Figure 45 shows the channel modifications observed at the sampling locations for the Glen Tay 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 46 depicts the dominant vegetation observed at the sampled headwater sites in the Glen Tay 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 47 depicts the type of riparian vegetation observed at the sampled headwater sites in the Glen Tay 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 Glen Tay catchment area. Figure 48 depicts the degree of sediment deposition observed at the sampled headwater sites in the Glen Tay 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 49 shows the feature roughness conditions at the sampling locations in the Glen Tay catchment were highly variable ranging from minimal to extreme.