3.0 Otty Lake Catchment: Riparian Conditions
The RVCA Stream Characterization Program evaluated 3.9 km of Jebbs Creek in 2016. A total of 39 stream survey assessments were completed in the month of June and the first week of July.
During the summer and fall of 2016, the Rideau Valley watershed experienced periods of severe drought. Precipitation levels were measured at less than 40% of the long-term average, as the water supply was unable to meet local demand. The lack of rainfall affected the success and function of farm crops, municipal and private wells, lawns and gardens, navigation and ultimately the health of our lakes, rivers and streams.
Low water conditions were readily observed throughout the watershed, as many of the streams were highly fragmented or completely dry (see photo below). Aquatic species such as amphibians, fish and benthic invertebrates were affected, as suitable habitat may have been limited.
Fragmentation of habitat was observed along Jebbs Creek at the Perth Wildlife Reserve during the summer and fall of 2016
3.1 Jebbs Creek 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 mitigate 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 26 demonstrates the buffer conditions of the left and right banks separately. Jebbs Creek had a buffer of greater than 30 meters along 91 percent of the right bank and 97 percent of the left bank.
Figure 26 Riparian Buffer Evaluation along Jebbs Creek
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 27). The riparian buffer zone along Jebbs Creek was found to be dominated by forest and wetland conditions along the riparian corridor.
Figure 27 Riparian buffer alterations along Jebbs Creek
3.1.3 Adjacent Land Use
The RVCA’s Stream Characterization Program identifies seven different land uses along Jebbs Creek (Figure 28). 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. Natural areas made up 96 percent of the stream, characterised by forest, scrubland, meadow and wetland. Wetland habitat was dominant in the adjacent lands along Jebbs Creek at 84 percent of the surveyed sections. The remaining land use consisted of industrial/commercial, residential and other in the form of hydro infrastructure.
Figure 28 Land Use along Jebbs Creek
3.2 Jebbs Creek 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 Jebbs Creek had low levels of erosion with the exception of one location along the system which had moderate levels of erosion near the confluence with the Tay marsh (Figure 29).
Figure 29 Stream erosion levels along Jebbs Creek
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 30 shows that Jebbs Creek had low levels of undercut banks along the majority of the system which is typical for systems that are dominated by riverine wetland habitat along the shoreline.
Figure 30 Undercut stream banks along Jebbs Creek
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 one metre above the water surface. Figure 31 shows highly variable conditions of none to high levels of stream shading along Jebbs Creek.
Figure 31 Stream shading along Jebbs Creek
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 32 shows that the majority of Jebbs Creek had low to moderate levels of instream wood structure in the form of branches and trees along the system.
Figure 32 Instream wood structure along Jebbs Creek
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 wood structure provide a food source, nutrients and shade which helps to moderate instream water temperatures. Figure 33 shows the system is dominated by low to moderate levels of overhanging branches and trees along Jebbs Creek.
Figure 33 Overhanging trees and branches along Jebbs Creek
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 34 shows 74 percent of Jebbs Creek remains “unaltered” with no anthropogenic alterations. Eighteen percent of Jebbs Creek was classified as natural with minor anthropogenic changes, while eight percent was considered altered. The alterations along Jebbs Creek were in the form of a road crossing and areas with reduced natural buffers.
Figure 34 Anthropogenic alterations along Jebbs Creek
3.3 Jebbs Creek 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 Perth Wildlife Reserve site on Jebbs Creek since 2003. Monitoring data is analysed for each sample site and the results are presented using the Family Biotic Index, Family Richness and percent Ephemeroptera, Plecoptera and Trichoptera. There were no values recorded for the Fall of 2016 due to extreme drought conditions therefore no samples could be collected.
OBBN sample location at the Perth Wildlife Reserve in the spring of 2016
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 Jebbs Creek catchment sample location at the Perth Wildlife Reserve are summarised by year from 2005 to 2016. “Fair” to “Poor” water quality conditions were observed at the Jebbs Creek sample location (Figure 35) using a grading scheme developed by Conservation Authorities in Ontario for benthic invertebrates.
Figure 35 Hilsenhoff Family Biotic Index at the Perth Wildlife Reserve 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 Jebbs Creek site is reported to have “Fair” family richness (Figure 36).
Figure 36 Family Richness at the Jebbs at the Perth Wildlife Reserve location
Ephemeroptera (Mayflies), Plecoptera (Stoneflies), and Trichoptera (Caddisflies) are species considered to be very sensitive to poor water quality conditions. A 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 moderately tolerant and tolerant to poorer water quality conditions at the Jebbs Creek sample location. As a result, the EPT indicates that the Jebbs Creek sample location is reported to have “Fair” to “Poor” water quality (Figure 37) from 2005 to 2016.
Figure 37 EPT at the Jebbs Creek at the Perth Wildlife Reserve sample location
Overall the Jebbs Creek sample location aquatic habitat conditions from a benthic invertebrate perspective is considered “Fair to Poor” from 2005 to 2016 as the samples are dominated by species that are moderately tolerant and tolerant 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 woody material.
Low to high habitat complexity was identified for Jebbs Creek (Figure 38). Regions with increased habitat complexity were observed in the lower and upper reaches of the system within the catchment.
Figure 38 Habitat complexity along Jebbs Creek
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 39 shows the overall presence of various substrate types observed along Jebbs Creek. Substrate conditions were somewhat diverse along Jebbs Creek with all substrate types being recorded at various locations along the creek. Silt was the dominant substrate type observed along Jebbs Creek which is consistent with riverine wetland habitat. Figure 40 shows the dominant substrate type observed for each section surveyed along Jebbs Creek.
Figure 39 Instream substrate along Jebbs Creek
Figure 40 shows the dominant substrate type along Jebbs Creek
3.3.4 Instream Morphology
Pools and riffles are important habitat features for aquatic life. Riffles are fast flowing areas characterised 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 characterised 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 centre of the channel. Figure 41 shows that Jebbs Creek is fairly uniform; 100 percent of sections recorded runs, five percent riffles and 33 percent of sections contained pool habitat. Figure 42 shows where the limited riffle habitat areas were observed along Jebbs Creek.
Figure 41 Instream morphology along Jebbs Creek
Figure 42 Riffle habitat locations along Jebbs Creek
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
- Stabilising 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. Floating plants were observed in 95% of sections surveyed, algae was observed in 90% of sections, narrow leaved emergents were present in 72% of the sections surveyed, while free floating plants were observed in 44% of surveyed sections. Broad leaved emergents were observed in 44% of sections, submerged plants in 56% and robust emergents in 15% of sections surveyed. Figure 43 depicts the plant community structure for Jebbs Creek. Figure 44 shows the dominant vegetation type observed for each section surveyed along the Jebbs Creek catchment.
Figure 43 Vegetation type along Jebbs Creek
Figure 44 Dominant vegetation type along Jebbs Creek
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 45 demonstrates that the Jebbs Creek reach had normal to common levels of vegetation recorded at 36 and 90 percent of stream surveys. Extensive levels of vegetation were observed along 64 percent of the surveyed sections and were consistent with areas dominated by the invasive plant known as European Frogbit.
Figure 45 Instream vegetation abundance along Jebbs Creek
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. One hundred percent of the sections surveyed along Jebbs Creek reach contained invasive species. The invasive species observed in Jebbs Creek were European frogbit and banded mystery snail. 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 46).
Figure 46 Invasive species abundance along Jebbs Creek
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 47 shows that the dissolved oxygen in Jebbs Creek supports warmwater and in certain locations coldwater biota along the system. The average dissolved oxygen levels observed within Jebbs Creek was 9.5mg/L which is well above the recommended levels for warmwater biota.
Figure 47 Dissolved oxygen ranges in Jebbs Creek
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 main stem of Jebbs Creek was 262.5 µs/cm. Figure 48 shows the conductivity readings for Jebbs Creek.
Figure 48 Specific conductivity ranges in Jebbs Creek
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 for Jebbs Creek averaged 7.94 thereby meeting the provincial standard (Figure 49).
Figure 49 pH ranges in Jebbs Creek
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 stabilise 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 summarised into 6 classes:
Dissolved oxygen conditions in Jebbs Creek varied along the system for both warm and coolwater species (Figure 50).
Figure 50 A bivariate assessment of dissolved oxygen concentration (mg/L) and saturation (%) in Jebbs Creek
22.214.171.124 Specific Conductivity Assessment
Specific conductivity (SPC) is a standardised 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 summarise 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 along the majority of Jebbs Creek, however there were moderately elevated areas in the middle reaches (Figure 51).
Figure 51 Relative specific conductivity levels along Jebbs Creek
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 52 shows where the thermal sampling site was located on Jebbs Creek. Analysis of the data collected indicates that Jebbs Creek is classified as a warm water system (Figure 53).
Figure 52 Temperature logger location on Jebbs Creek
Figure 53 Temperature logger data for the site on Jebbs Creek
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 54 shows areas where one or more of the above groundwater indicators were observed during stream surveys and headwater drainage feature assessments.
Figure 54 Groundwater indicators observed in the Otty Lake catchment
3.3.11 Fish Community
The Otty Lake catchment is classified as a mixed community of warm and cool water recreational and baitfish fishery with 19 species observed. Figure 55 shows the historical and 2016 fish sampling locations in the catchment.
Figure 55 Otty Lake catchment fish community
Table 13 is a list of species observed in the watershed historically and during the 2016 sampling effort.
Fish species observed in the Otty Lake catchment
RVCA staff setting a fyke net at County Road 1 on Jebbs Creek in May 2016
Greater redhorse (Moxostoma valenciennesi) captured and released while fyke netting on Jebbs Creek adjacent to the Perth Wildlife Reserve
3.3.12 Migratory Obstructions
Migratory obstructions represent limitations to fish dispersal within a system and may restrict access to important spawning and rearing habitat. Migratory obstructions can be natural or manmade, and they can be permanent or seasonal. Figure 56 shows the migratory obstructions observed for the Otty Lake catchment.
Figure 56 Migratory obstructions in the Otty Lake catchment
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 fields and may also be considered potential barriers to fish migration. Figure 57 shows the types of beaver dams that were identified on the surveyed portions of Jebbs Creek in 2016.
Figure 57 Beaver Dam locations in the Otty Lake catchment
3.4 Headwater Drainage Feature Assessment
3.4.1 Headwaters Sampling Locations
The RVCA Stream Characterization program assessed Headwater Drainage Features for the Otty Lake 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 32 sites at road crossings in the Otty Lake catchment area (Figure 58).
Figure 58 Location of the headwater sampling sites in the Otty Lake 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 Otty Lake catchment are primarily classified as wetland and natural features. Figure 59 shows the feature type of the primary feature at the sampling locations.
Figure 59 Headwater feature types in the Otty Lake catchment
A spring photo of the headwater sample site on Mackler Side Road
A summer photo of the headwater sample site on Mackler Side Road
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 60 shows the observed flow condition at the sampling locations in the Otty Lake catchment in 2017.
Figure 60 Headwater feature flow conditions in the Otty Lake 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. Figure 61 shows the channel modifications observed at the sampling locations for the Otty Lake. The majority of the headwater features had no modifications observed at the sample locations.
Figure 61 Headwater feature channel modifications in the Otty Lake 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 vegetation 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 fish and wildlife habitat. The following classifications are evaluated no vegetation, lawn, wetland, meadow, scrubland and forest. The features assessed were classified as being dominated by wetland and meadow. Figure 62 depicts the dominant vegetation observed at the sampled headwater sites in the Otty Lake catchment.
Figure 62 Headwater feature vegetation types in the Otty Lake 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. The sample locations were dominated by natural vegetation. Figure 63 depicts the type of riparian vegetation observed at the sampled headwater sites in the Otty Lake catchment.
Figure 63 Headwater feature riparian vegetation types in the Otty Lake 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. Conditions ranged from no deposition observed to extensive deposition recorded. Figure 64 depicts the degree of sediment deposition observed at the sampled headwater sites in the Otty Lake catchment.
Figure 64 Headwater feature sediment deposition in the Otty Lake 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 debris 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 to aquatic organisms. Figure 65 shows the feature roughness conditions at the sampling location in the Otty Lake catchment.
Figure 65 Headwater feature roughness in the Otty Lake catchment