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3.0 Perth Catchment: Riparian Conditions

The RVCA Stream Characterization Program surveyed 4.6 kilometres (46 sections) of the Tay River in July 2017 within the Perth catchment.

In 2017 the Tay River subwatershed experienced high water levels along the Tay River and its tributaries. 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. Precipitation was close to normal in the Tay River watershed in January, 2017. Most of the rest of the year, however, the area got much more than normal. For the year the total precipitation was over 130% of normal. The spring snowmelt peak flow was an above average 57 cubic metres per second (cms) in Perth on April 6. Flows receded there until more than 100 mm of rain fell over the first week of May causing a peak flow on May 7 of 71 cms, a flow not previously reached in the 24 years of records. Flows increased once again at the end of October as a result of another heavy rainfall totaling 124 mm over nine days that caused a considerable delay in construction of the rocky ramp replacement for the Haggart Island Dam.

Flooding along the Tay River in Stewart Park during the spring of 2017

3.1 Perth Catchment Overbank Zone

3.1.1 Riparian Land Cover 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 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 65 percent of the left bank and 46 percent of the right bank.

Figure 9 Riparian Buffer Evaluation along the Tay River in the Perth 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, wetlands and meadow conditions. There were several areas that had altered riparian zone conditions along the Tay River. These areas included shoreline modifications in the form of armour stone, wooden retaining walls, gabion baskets, concrete and rip rap. Modifications also included a number of road crossings and areas with reduced natural vegetated buffer conditions. Opportunities for shoreline buffer enhancements along the Tay River in the Town of Perth catchment should be explored and implemented where possible.

Figure 10 Riparian buffer alterations along Tay River in the Perth catchment

3.1.3 Adjacent Land Use

The RVCA’s Stream Characterization Program identifies nine different land uses along the Tay River in the Town of Perth (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. Scrubland habitat was dominant at 91 percent; forest and wetlands were found along 61 percent of the surveyed sections and 11 percent meadow habitat was present along the Tay River. The remaining land use consisted of residential, recreational, industrial/commercial and infrastructure in the form of road crossings.

Figure 11 Land Use along the Tay River in the Perth catchment

3.2 Perth Catchment 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 had no erosion observed along the majority of surveyed sections with a few small sections having low levels of erosion (Figure 12).

Figure 12 Erosion levels along the Tay River in the Perth 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 lower reach with low levels of undercut banks.

Figure 13 Undercut stream banks along the Tay River in the Perth 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 Tay River. Stream shading conditions were fairly uniform along the Tay River ranging from no overhead canopy cover to low levels. There were two areas along the Tay River that reached moderate levels of stream shading.

Figure 14 Stream shading along the Tay River in the Perth 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 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.

Shoreline Protection
  • 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
Food Source
  • 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 in the upper reach which were characterized as having moderate levels of instream wood structure in the form of branches and trees along the system.

Figure 15 Instream wood structure along the Tay River in the Perth 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 wood structure provides 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.

Figure 16 Overhanging wood structure along the Tay River in the Perth 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 fifteen percent of the Tay River remains “unaltered” with no anthropogenic alterations. Forty six percent of the Tay River was classified as natural with minor anthropogenic changes. Thirty five percent of survey sections were classified as being altered and four percent was classified as highly altered. These areas consisted of sections with shoreline modifications and road crossings.

Figure 17 Anthropogenic alterations along the Tay River in the Perth catchment

3.3 Perth Catchment Instream Aquatic Habitat

3.3.1 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.

Low to high habitat complexity was identified for the Tay River in the Town of Perth catchment (Figure 18). Regions with increased habitat complexity were observed in the upper and middle reaches of the system within the catchment.

Figure 18 Habitat complexity along the Tay River in the Perth 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 with all substrate types being recorded at various locations along the system (Figure 19). Figure 20 shows the dominant substrate type observed for each section surveyed along the Tay River.

Figure 19 Instream substrate along the Tay River in the Perth catchment
Figure 20 shows the dominant substrate type along the Tay River in the Perth 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 21 shows that the Tay River is somewhat uniform; 100 percent of sections recorded runs, 57 percent pools and 7 percent riffles. Figure 22 shows where the limited riffle habitat areas were observed along the Tay River.

Figure 21 Instream morphology along the Tay River in the Perth catchment
Figure 22 Instream riffle habitat along the Tay River in the Perth 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 dominant in this reach of the Tay River and were observed at 100 percent of surveyed sections. Broad leaved emergents were observed in 85 percent of sections, 78 percent floating plants, 76 percent narrow leaved emergents, 72 percent of sections contained algae, 63 percent free floating, while robust emergents were present in 54 percent of the survey sections. Figure 23 depicts the plant community structure for the Tay River. Figure 24 shows the dominant vegetation type observed for each section surveyed along the Tay River in the Perth catchment.

Figure 23 Vegetation type along the Tay River in the Perth catchment
Figure 24 Dominant vegetation type along the Tay River in the Perth 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 25 demonstrates that the Tay River had normal to common levels of vegetation recorded at 89 and 57 percent of stream surveys. Extensive levels of vegetation were observed in 59 percent of the surveyed sections, while twenty eight percent of sections had no vegetation in areas that were dominated by bedrock substrate conditions.

Figure 25 Instream vegetation abundance along the Tay River in the Perth 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. Eighty nine percent of the sections surveyed along the Tay River in the Perth catchment had invasive species. The invasive species observed were common/glossy buckthorn, banded mystery snail, bull thistle, curly leafed pondweed, dog strangling vine, Eurasian milfoil, European frogbit, Himalayan balsam, honey suckle, Manitoba maple, wild parsnip and purple loosestrife. 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 26).

Figure 26 Invasive species abundance along the Tay River in the Perth 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. 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 27 shows that the dissolved oxygen in Tay River supports warmwater and coolwater biota along the system. The average dissolved oxygen level observed within the Perth catchment was 7.0mg/L which meets the recommended level for warm and cool water biota.

Figure 27 Dissolved oxygen ranges along the Tay River in the Perth catchment Conductivity

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 198.3 µs/cm. Figure 28 shows the conductivity readings for the Tay River in the Perth catchment.

Figure 28 Specific conductivity ranges along the Tay River in the Perth catchment pH

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 7.4 thereby meeting the provincial standard (Figure 29).

Figure 29 pH ranges along the Tay River in the Perth catchment 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 were fairly uniform along the system for both warm and coolwater species (Figure 30).

Figure 30 A bivariate assessment of dissolved oxygen concentration (mg/L) and saturation (%) along the Tay River in the Perth catchment 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 elevated areas in the upper and lower reaches (Figure 31). Two sections had high conductivity levels observed in the lower reach and several sections had moderate levels observed also in the lower reach.

Figure 31 Relative specific conductivity levels along the Tay River in the Perth 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 32 shows where the thermal sampling sites were located on the Tay River in the Perth catchment. Analysis of the data collected indicates that the Tay River is classified as a warm water system (Figure 33).

Figure 32 Temperature logger locations along the Tay River in the Perth catchment
Figure XX Temperature logger data for the sites along the Tay River in the Perth catchment
Figure 33 Temperature logger data for the sites along the Tay River in the Perth 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

3.3.10 Groundwater

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 34 shows areas where one or more of the above groundwater indicators were observed during stream surveys and headwater assessments.

Figure 34 Groundwater indicators observed in the Perth catchment

3.3.11 Fish Community

The Perth catchment is classified as a mixed community of warm and cool water recreational and baitfish fishery with 27 species observed (Figure 35).

Figure 35 Fish community sampling observations in the Perth catchment

Table 6 contains a list of fish species observed in the Perth catcmment.

Table 6 Fish species observed in the Perth catchment
Fish SpeciesScientific NameFish codeHistorical201520162017
banded killifishFundulus diaphanusBaKilXXX
black crappiePomoxis nigromaculatusBlCraX
blackchin shinerNotropis heterodonBcShiXX
blacknose daceRhinichthys atratulusBnDacX
blacknose shinerNotropis heterolepisBnShiX
bluegillLepomis macrochirusBluegX
bluntnose minnowPimephales notatusBnMinXXXX
brassy minnowHybognathus hankinsoniBrMinX
brook sticklebackCulaea inconstansBrStiXX
brown bullheadAmeiurus nebulosusBrBulXXXX
bullhead catfish hybridsIctaluridae familyHy650X
burbotLota lotaBurboXX
carps and minnowsCyprinidaeCA_MIXX
central mudminnowUmbra limiCeMudXXXX
common carpCyprinus carpioCoCarX
common shinerLuxilus cornutusCoShiXXXX
creek chubSemotilus atromaculatusCrChuXXX
etheostoma sp.etheostoma sp.EthSpXXXX
fallfishSemotilus corporalisFallfXXX
fathead minnowPimephales promelasFhMinX
golden shinerNotemigonus crysoleucasGoShiX
greater redhorseMoxostoma valenciennesiGrRedX
hornyhead chubNocomis biguttatusHhChuXXX
largemouth bassMicropterus salmoidesLmBasXX
logperchPercina caprodesLogpeXXX
longnose daceRhinichthys cataractaeLnDacX
northern pikeEsox luciusNoPikXXX
northern redbelly daceChrosomus eosNRDacX
pumpkinseedLepomis gibbosusPumpkXXXX
rock bassAmbloplites rupestrisRoBasXXXX
shorthead redhorseMoxostoma macrolepidotumShRedX
smallmouth bassMicropterus dolomieuSmBasXXX
sunfish familyLepomis sp.LepSpX
stonecatNoturus flavusStoneX
tadpole madtomNoturus gyrinusTaMadX
walleyeSander vitreusWalleX
white suckerCatostomus commersoniiWhSucXXX
yellow bullheadAmeiurus natalisYeBulXXXX
yellow perchPerca flavescensYePerXX


RVCA staff measuring and weighing fish while sampling on the Tay River in the Perth catchment
A fyke net set along the Tay River in the Perth catchment in July of 2017

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 36 shows that the Perth catchment had one weir and one man made dam on the Tay River at the time of the survey in 2017.

Figure 36 Migratory obstructions in the Perth catchment
A weir located on the Tay River in the Perth catchment

3.4 Headwater Drainage Feature Assessment

3.4.1 Headwaters Sampling Locations

The RVCA Stream Characterization program assessed Headwater Drainage Features for the 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 7 sites at road crossings in the Perth catchment area (Figure 37).

Figure 37 Locations of the headwater sampling sites in the Perth 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 Perth catchment are highly variable. Figure 38 shows the feature type of the primary feature at the sampling locations.

Figure 38 Headwater feature types in the Perth 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 39 shows the observed flow condition at the sampling locations in the Perth catchment.

Figure 39 Headwater feature flow conditions in the Perth catchment
A spring photo of the headwater sample site in the Perth catchment located on Hands Road
A summer photo of the headwater sample site in the Perth catchment located on Hands Road

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 Perth catchment area had four features with no channel modifications observed and three features as having been historically dredged or channelized. Figure 40 shows the channel modifications observed at the sampling locations for the Perth catchment.

Figure 40 Headwater feature channel modifications in the Perth 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 41 depicts the dominant vegetation observed at the sampled headwater sites in the Perth catchment.

Figure 41 Headwater feature vegetation types in the Perth 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 42 depicts the type of riparian vegetation observed at the sampled headwater sites in the Perth catchment.

Figure 42 Headwater feature riparian vegetation types in the Perth 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 Perth catchment area. Figure 43 depicts the degree of sediment deposition observed at the sampled headwater sites in the Perth catchment. Sediment deposition conditions ranged from no sediment deposition to substantial.

Figure 43 Headwater feature sediment deposition in the Perth 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 44 shows the feature roughness conditions at the sampling locations in the Perth catchment were highly variable ranging from minimal to extreme.

Figure 44 Headwater feature roughness in the Perth catchment