Sixteen Mile Creek Tributaries - Meander Belt Width Assessment · PDF file · 2013-05-09Sixteen Mile Creek Tributaries Meander Belt Width Assessment Status: Final Report Version:

Sixteen Mile Creek Tributaries Final Report Meander Belt Width Assessment January 2012

PARISH Geomorphic Ltd. Page 0

SSIIXXTTEEEENN MMIILLEE CCRREEEEKK TTRRIIBBUUTTAARRIIEESS TTHHEE CCAATTHHOOLLIICC CCEEMMEETTEERRIIEESS OOFF

TTHHEE DDIIOOCCEESSEE OOFF HHAAMMIILLTTOONN --MMEEAANNDDEERR BBEELLTT WWIIDDTTHH AASSSSEESSSSMMEENNTT ––

FFIINNAALL RREEPPOORRTT

Report to: Director of Cemeteries Catholic Cemeteries of the Diocese of Hamilton 600 Spring Gardens Road Burlington, ON. Attention: John O’Brien From: Benjamin Swanson., M.Sc. and John Parish, P.Geo. Report No.: 01-11-39

Date: November 2009 (Addendum – October 2010); Updated January 2012)



2500, Meadowpine Blvd. Suite 200 Address Mississauga, Ontario, L5N 6C4

Canada (905) 877-9531 Telephone (905) 877-4143 Fax

www.parishgeomorphic.com Internet

Drafted by: Benjamin Swanson, M.Sc Checked by: John Parish, P. Geo.

Date checked: January, 2012 Approved by: John Parish, P.Geo.

Date of approval: January, 2012

Document Title:

Sixteen Mile Creek Tributaries Meander Belt Width Assessment

Status: Final Report Version: 03

Date: January 2012 Project name: Diocese of Hamilton Cemetery –

Meander Belt Width Assessment Project

number: 01-11-39

Client: Diocese of Hamilton Reference: 01-11-39/03



1.0 INTRODUCTION The Catholic Cemeteries of the Diocese of Hamilton has plans to implement a new cemetery on the

103 acre property located on the northwest quadrant of the intersection of Bronte Road and Lower

Baseline Road, in Milton (Figure 1). Conservation Halton has requested that a meander belt width

study be completed for four Sixteen Mile Creek tributaries to ensure that the proposed land use

planning does not fall within hazardous land as detailed in the Provincial Policy Statement 3.1.1. A

meander belt width assessment report dated November 2009 (addendum - October 2010) was

submitted and reviewed by Conservation Halton. As part of the meander belt width assessment and

this update, the following tasks were undertaken:

• Collect and review available background information, including relevant studies, aerial

photographs and mapping;

• Delineate reaches within the identified study area;

• Based on aerial photographs, establish preliminary meander belt widths on a reach basis,

following the orientation of the valley;

• Where appropriate and feasible, complete a 100-year erosion analysis to identify the necessary

setbacks or belt width allowance; and

• Complete a field reconnaissance including rapid assessments in order to confirm the existing

appropriateness of reach boundaries, 100-year erosion rates, and the meander belt width for

each tributary

• Respond to Conservation Halton review comments dated April 8, 2011 (summarized in

Appendum, section 11).



Figure 1: Study areas located at the intersection of Lower Baseline Rd. and Bronte Rd. (Google

Imagery, 2009)

2.0 BACKGROUND REVIEW Previous investigations conducted for the study areas were evaluated for the purpose of the meander

belt width assessment. Past reports provide valuable insight to the historical conditions of the study

area and provide results which may be used to validate geomorphological alterations and/or confirm

any inconsistencies found within the collected data. Although several past reports were evaluated,

including many involving Sixteen Mile Creek, the extent of the investigations did not include the

current study site. In such cases, aerial photographs and results from rapid field assessments are

utilized to characterize the geomorphic conditions of the tributaries and develop the meander belt

widths.



3.0 REACH DELINEATION The amount and size of sediment inputs, valley shape, land use or vegetation cover, and other

parameters that influence channel form often change as you move downstream along a waterway.

In order to account for these changes, channels are often separated into “reaches”. Reaches can be

defined as stretches of channel that flow through a nearly constant valley setting and incorporate

similar physical characteristics along their lengths. Thus, reaches experience similar controlling and

modifying influences, which are reflected in similar geomorphological form, function, and process.

The delineation of a reach considers sinuosity, gradient, hydrology, local geology, degree of valley

confinement, and vegetative control using methods outlined in Parish Geomorphic Ltd. (2001).

The following sections describe delineated reach characteristics and Table 1 provides additional

details.

Figure 2: Reach delineations for the study area. Orange lines represent breaks between reaches.



Table 1: Reach Characteristics for Study Site

Reach Length (m) Sinuosity Slope SMT-1a 211 1.09 0.002

SMT-1b 230 1.05 0.005

SMT-1c 279 1.02 0.009

SMT-2 579 1.03 0.006

SMT-3H 221 1.05 0.011

SMT-4 648 1.04 0.009

SMT-5 230 1.24 0.016

3.1 REACH SMT-1 Reach SMT-1 extends from its confluence with reach SMT-2, immediately upstream of the Bronte

Rd. culvert crossing, and proceeds upstream to where the land use changes from agricultural to

residential at the single dwelling home located along Lower Baseline Rd. The reach is divided into

an upper, middle, and lower section, SMT-1c, SMT-1b, and SMT-1a, respectively. The reaches were

delineated based on confluences with reach SMT-4 and SMT-2, which represent changes to the local

hydrology. The delineation of SMT-1c is based on the forementioned change in local land use from

residential to agricultural. Reach SMT-1b and SMT-1c have a straightened meander planform which

could be described as swale features. SMT-1a however, exhibits a more defined, meandering

channel planform as it moves downstream, and especially within the vicinity of the Bronte Rd.

culvert crossing. An open scrub meadow buffered the channel through the extent of the agricultural

fields, with manicured lawn lining SMT-1c.

3.2 REACH SMT-2 Reach SMT-2 extends from its confluence with reach SMT-1, immediately upstream of the Bronte

Rd. culvert crossing, and proceeds upstream to the north limits of the agricultural field. The reach

was delimited downstream at its confluence with reach SMT-1 which represents an alteration to the

local hydrology, and upstream, where the channel becomes undefined along the north limits of the

study area. Reach SMT-2 is a straightened channel which could be described as a swale feature.

Like SMT-1, it had a more defined, meandering channel planform just upstream of the Bronte Rd.

culvert crossing. The channel banks along SMT-2 were steepened and the land cover within the



proposed study area consists primarily of agricultural practices. An open scrub meadow buffered

the swale through the extent of the field. Instream vegetation was present within the channel closer

to the Bronte Rd. culvert.

3.3 REACH SMT-3H (HISTORICAL CHANNEL) Reach SMT-3H historically extends from the culvert crossing at Lower Baseline Rd., approximately

110m west of the Bronte Rd. and Lower Baseline Rd. intersection, to its confluence with reach

SMT-1. Reach SMT-3H displayed no meandering planform or defined channel configuration

through the cultivated land in which it was situated. However, Conservation Halton’s Approximate

Regulation Mapping shows a regulation limit following the historic location/flow path.

3.4 REACH SMT-3 (ALTERNATE CHANNEL) Because SMT-3H has been altered and diverted, without Conservation Halton permission, the

regulation limit associated with the historic channel (SMT-3H) are now associated with SMT-3.

Reach SMT-3 is a constructed channel cut sometime between 1978 and 2004. It is a straight

watercourse running from the culvert crossing at Lower Baseline Rd to its confluence with reach

SMT-1, approximately 70 m upstream of the historic SMT-3H and SMT-1 confluence. Reach SMT-

3 displays no meandering planform or defined channel configuration through the cultivated field it

was built in. It is primarily lined with grass.

3.5 REACH SMT-4 Reach SMT-4 flows almost directly east from its upstream end at the property boundary to its

junction with SMT-1. Like the other reaches, the channel is severely impacted by agricultural

practices. It has been straightened and plowed, and in much of the reach exhibits swale-like

features, as opposed to an established channel. The channel banks along SMT-4 were steepened

and the land within the proposed study area is used primarily for crops. An open, narrow, weedy,

grassy area appears to buffer the swale on the 2004 photograph, but it appears to be plowed through

on the 2009 photo.



3.6 REACH SMT-5 (DOWNSTREAM OF SITE) Reach SMT-5 was included for comparison purposes, and in part, to address the conservation

authority’s comment on the November 2009 study. It is situated downstream of the Bronte Road

culvert crossing. The channel flows along a residential building and yard before entering the

Rattlesnake Point Golf Club. Compared to the upstream reaches, a much more defined meandering

pattern characterizes the waterway along this reach. A steeper slope and the combined flow from

SMT-2 and SMT-1 result in more meandering and a slightly higher erosion rates in this reach, as

expected; however, comparisons between SMT-5 and the other tributary channels are tenuous due

to these differences as well. The larger flow and steeper slopes lead to greater stream energy and

different hydraulic characteristics, leaving a much different channel form than exhibited by the

smaller, flatter upstream channels.

4.0 GENERAL HISTORIC ASSESSMENT To understand the current state of a channel, it is important to consider the changes it has

undergone in the past, including changes in surrounding landuse. In the study area, these landuse

changes were identified through an historical assessment using sequential aerial photos. Photographs

used for this investigation were taken from 1978, 2004, and 2009. Previous work also included an

air photo acquired in 1972 and 2005; however, these photographs could not be located for this

updated report. Additionally, a 1954 image was obtained for the study, but scale and shadow issues

made it unusable for detailed examination.

Observations made on the 1978 aerial photographs of the study area demonstrate little change with

respect to landuse coverage change when compared to the later 2004 and 2009 photos (Figure 1, 3,

and 4). The lands surrounding the study area in 1978 were dedicated to agricultural land use, with a

single dwelling home located at the south-west limit of the property along Lower Baseline Rd. By

2004, the lands surrounding the study site were still dominated by agriculture but had a few more

dwellings situated throughout the surrounding areas. One prevalent difference between the 1978

and 2004 photos was the development of the Rattlesnake Point Golf Club located east of Bronte

Rd, downstream of the study area. However, this change would likely have no impact on the

upstream channels.



5.0 HISTORIC ASSESSMENT – CHANNEL PLANFORM ALTERATIONS Historic migration rates are a useful indicator of planform adjustment and provide a means of

quantifying the rate of channel widening or bank erosion over time. Any change to the hydrologic

conditions within a catchment can result in a modified flow regime. Long-term, non-local changes

such as precipitation patterns result in gradual changes to channel morphology. In the short-term,

changes in land use can have more abrupt consequences. In particular, urbanization generally leads

to increased peak discharges which ultimately results in increased erosion and, hence, more rapid

changes in channel morphology as the system attempts to re-establish a state of dynamic

equilibrium. Consequently, the amplitude of meanders may increase as the planform geometry

adjusts to the newly imposed flows.

Figure 3: Study areas located at the intersection of Lower Baseline Rd. and Bronte Rd -2004 aerial photograph.



5.1 METHODOLOGY A common method for measuring changes in channel and bank position over time is to compare

bank locations on sequential aerial photographs. Distances between each year’s banks and known

points, or relative to an initial position, can be measured and used to estimate bank erosion rates.

Because air photos acquired at different times are often taken at different scales they are often

digitally scanned and georeferenced in a geographic information system (GIS) for more direct

comparison and efficient and accurate measurement. Within the GIS, channel positions can be

digitized on the sequential photographs, and overlaid on the same map for evaluation (Figure 5).

This method is especially useful if a trend in bank position or erosion direction is evident.

However, measurements of bank erosion taken from aerial photographs are often inaccurate. They

include errors in photo interpretation from tree cover, scale issues, shadows, etc; distortions within

the photographs related to the pitch and yaw of the aircraft during flight; and a lack of common,

hard control points to georeference photos and remove these distortions. Additionally, many of the

same problems often make locating smaller channels next to impossible. Cumulatively, these issues

can lead to errors of a half meter to tens of meters. While georeferencing, care is taken to reduce

distortions and align the photographs as well as possible, but some error always remains.

Along the study tributaries, lateral migration rates were determined for prominent meander bends

using methods outlined in Geomorphic Protocols for Subwatershed Studies (PARISH, 2001). These

protocols dictate that channel banks are first delineated and then compared for channel width

changes or measurable offsets in planform position. Much of the work was conducted using GIS

software (ESRI ArcInfo 9.2). Migration rates were calculated by comparing digitized channel

locations from the 1978 and 2009 aerial imagery. This method differs from the November 2009

report where the 1972 and 2005 measurements were taken manually from the original, unaligned

photographs. Several measurements were taken along visible meander bends at the widest point of

offset between the 1978 and 2009 channels. Almost all the offset observed in the updated study was

due to lateral erosion, although minor downstream erosion occurs along SMT-5. The November

2009 study (Table 2) provides estimates of downstream erosion rates, but the updated data

concentrates on lateral migration. The focus bends were located at the downstream end of the

reaches, were the channel seems to be more freely meandering, as opposed to sections where the

stream has likely been straightened or plowed. The results of the assessment are summarized in



Table 3. Because the 1978 photograph was acquired at a large scale, and locating the actual

channel position within some of the larger, straightened segments on both the 1978 and 2009

photographs proved difficult, measurements of channel migration were generally within the error.

Figure 4: Study areas located at the intersection of Lower Baseline Rd. and Bronte Rd -1978 aerial photograph.



5.2 RESULTS AND EROSION RATES Rates from the 1972 to 2005 study period, provided in Table 2, indicated relatively low levels of

erosion. For the 1978-2009 time frame, visual observations of the channel planform indicate the

watercourses have not undergone any major adjustments (Figure 5), although maximum bank

erosion rates were estimated to be slightly higher than the rates calculated for the 1972-2005 period

in the November 2009 study. Along SMT-1, maximum rates reached 0.16 m/yr, and for SMT-2, the

highest measured rate was 0.15 m/yr (Table 3), as opposed to maximum rates of 0.08 m/yr and

0.04 m/yr for SMT-1 and SMT-2, respectively, in the previous version of this study. The difference

in the erosion rate results for the two evaluations is likely due to differences between measuring

within the GIS and making manual measurements from the air photos.

Channel locations appear to have shifted along SMT-1a, presumably due to the creation of SMT-3

(alternative channel) and a channel realignment conducted at the confluence of SMT-1 and SMT-4.

Except for this confluence, very few changes occurred along SMT-4 over the 1978-2009 period, and

erosion rates were estimated between 0 and 0.07 m/yr. SMT-3 (alternative channel) also

experienced little change, at least between 2004 and 2009. The historic SMT-3H reach was difficult

to delineate on the air photos, presumably because it is just a swale after being diverted to SMT-3.

Although it appeared to be stable over the last half decade, it may have moved, or been moved, over

the longer 1978-2004 photo period. Neither SMT-3 reaches were included within the migration rate

analysis because channel planform was not observable on the 1978 (or 1972) aerial photos; hence,

no comparison could be made with the later images.

Overall, the calculated migration rates suggest the channels remained stable for the study period

despite intensive adjacent landuse. The channel configuration may have been maintained by

mechanical means over that time, but the air photos indicate some natural variability in planform

and the patterns remain consistent over the study period, even at the freely meandering downstream

ends of SMT-1 and SMT-2. Erosion rates along the less impacted meanders along SMT-5 ranged

between 0 and .08 m/yr between 1978 and 2009. Erosion along the SMT-5 channel may be more

realistic for the upstream reaches as well, because SMT-5 is under less intensive landuse pressure and

may represent a more recovered system. However, the larger drainage area associated with SMT-5

(i.e., higher flows and steeper slopes), likely make the comparison moot.



Table 2: Lateral and downstream migration rates for Reach SMT-1 & SMT-2 (1972-2005) from the November 2009 study.

Migration Rates

Reach SMT-1

(1972-2005)

Reach SMT-2

(1972-2005)

Lateral

(m/yr)

Downstream

(m/yr)

Lateral

(m/yr)

Downstream

(m/yr)

Min 0.012 0.09 0.012 0.09

Max 0.078 0.053 0.039 0.09

Mean .084 0.037 0.026 0.09

Table 3: Lateral migration rates for study area (1978-2009). Bracketed numbers represent undefined channels.

Migration Rates (m/yr)

Reach Maximum Mean (n = 6)

SMT-1a 0.16 0.09

SMT-1b 0.11 0.07

SMT-1c 0.06 0.03

SMT-2 0.15 0.06

SMT-3H (0.07) (0.04)

SMT-3 (0.04) (0.02)

SMT-4 0.07 0.02

SMT-5 0.08 0.04



Figure 5: Comparison of channel planform, 1978, 2004, and 2009. Channels remained fairly stable, except for a modification along SMT-1a and related downstream adjustment.

6.0 RAPID ASSESSMENTS In order to provide insight regarding existing geomorphic conditions, a site reconnaissance was

conducted in October, 2009. Rapid channel assessment techniques (RGA and RSAT) were applied

to determine the dominant geomorphic processes affecting each site. A Rapid Geomorphic

Assessment (RGA) documents indicators of channel instability (MOE, 1999). Observations are

quantified using an index that identifies channel sensitivity based on evidence of aggradation,

degradation, and channel widening and planimetric adjustment. The index produces values that

indicate whether the channel is stable/in regime (score <0.20), stressed/transitional (score 0.21-0.40)

or adjusting (score >0.41).



A Rapid Stream Assessment Technique (RSAT) survey provides a broader view of the system by

also considering the ecological functioning of the stream (Galli, 1996). Observations include in-

stream habitat, water quality, riparian conditions, and biological indicators, in addition to measures

of channel stability such as erosion and deposition. RSAT scores rank the channel as maintaining a

low (<20), moderate (20-35) or high (>35) degree of stream health. Table 4 provides a summary of

the rapid assessment results, while Appendix A provides a photographic record of site conditions at

the time of survey.

Table 4: Summary of RGA and RSAT scores for the study area.

Reach/Crossing RGA Condition RSAT Stability

SMT-1 (a,b,c) 0.1 In Regime 20 Moderate

SMT-2 0.1 In Regime 20 Moderate

SMT-3 (Alternate) 0.18 In Regime 28 Moderate

SMT-4 0.12 In Regime 22 Moderate

6.1 REACH SMT-1

Bankfull widths along this section of channel ranged from 1-2 m and bankfull depths ranged from

0.1-0.4 m. Substrate throughout the reach consisted of a mixture of silt, fine sands, and clay. No

defined pool-riffle sequences were notable along the reach and the much of the channel was

vegetated with tall grasses and cattails. RGA results indicated that the channel was ‘In Regime’;

however minor evidence of aggradation and planimetric form adjustment was present.

6.2 REACH SMT-2

Bankfull widths along this section of channel ranged from 1-2 m and bankfull depths ranged from

0.3-0.5 m. Substrate throughout the reach consisted of a mixture of silt, fine sands, and clay. No

defined pool-riffle sequences were notable along the reach and the much of the channel was

vegetated with tall grasses and cattails. RGA results indicated that the channel was ‘In Regime’;

however minor evidence of aggradation and planimetric form adjustment was present.



6.3 REACH SMT-3

Historically, reach SMT-3(H) conveyed flows through the east corner of the study area. The

channel has since been disturbed by the agricultural practices conducted on the land which has

caused the channel to lose its natural channel planform and cross-section configuration. Based on

observations obtained during the field reconnaissance, the historical flow regime conveyed by reach

SMT-3H has been re-routed to an alternate drainage ditch located to the west. The alternate

drainage ditch (SMT-3 alternative) begins approximately 110 m west of Bronte Rd., at a Lower

Baseline Rd. culvert, and connects, mid-reach, with SMT-1. The straight, alternate SMT-3 channel

corridor was well vegetated with grasses and weeds and was bordered by row crops. The low flow

channel within the corridor had a meandering planform and was fairly entrenched within the

channel corridor. Evidence of erosion was present along the outside meanders.



7.0 MEANDER BELT WIDTH DELINEATION In support of both the Provincial Policy Statement and the Valley and Stream Corridor Management

Program, the Toronto and Region Conservation Authority (TRCA) has produced a detailed

document which outlines Belt Width Delineation Procedures (PARISH Geomorphic Ltd., 2004) for

confined and unconfined systems. This document provides a process-based methodology for

determining the meander belt width for watercourses within the jurisdiction of the TRCA based on

background information, historic data (including aerial photography), degree of valley confinement

and channel planform.

7.1 PRELIMINARY MEANDER BELT WIDTH

7.1.1 Planform analysis Initial delineation of the meander belts were undertaken as recommended by Leopold and Wolman

(1960). The method prescribes drawing tangential lines along the outside bends of laterally extreme

meanders within the reach, parallel to the meander axis. The distance between these two lines

represents the meander belt width. The assessment was conducted using the digital images,

topographic maps, and historic channel positions. By using this approach, preliminary belt widths

were determined for all eight reaches within the study area.

Reaches SMT-1a and -1b had estimated meander belt widths of 18 m and 16 m, respectively, and

SMT-1c had a meander belt width of 12 m. The belt width for SMT-2 was also estimated at 18 m,

and 16 m was the estimated width for SMT-4. At the SMT-3 reaches, the final belt widths were

estimated at 14 m for the historical channel (SMT-3H) and 12 m for the current channel, SMT-3

(alternate). Table 6 provides a summary of these values.

In order to ensure that the meander belt width dimension delineated for the reaches were sufficient

to capture the planform of the study area channels over the historic record, an overlay of channel

location for the years 1978, 2004, and 2009 was completed. Results of this evaluation confirm that

the belt widths are an appropriate dimension and sufficient to support the geomorphic form and

function of the watercourses, especially considering the relatively low rates of change over the study

period (Figure 6).



Figure 6: Meander Belt Widths for Study Area including historic meander patterns. Additional detail provided in Figures 7-9.

7.1.2 Empirical Formulas In addition to defining meander belts on the air photos and topographic maps, empirical formulas

were also used to estimate meander belt widths. Formulas for calculating meander belt widths have

been created based on mathematical comparisons (i.e., regression) of field data describing channel

parameters, such as width, slope, and drainage area. They are “best fit” equations subject to data

quality, collection location, variability, and other factors which may result in poor accuracy. Some of

the more commonly used formulas include those devised by Williams (1986), Ward (2002), and for

local streams, TRCA/PARISH Geomorphic Ltd. (2004). Considering the poorly defined nature of

these channels, and the pressure placed on them by the adjacent agriculture, these three equations,



and other equations suitable for such small systems, were applied to the system of tributaries on the

site. Because exact field data were not available, except at SMT-3, estimates of channel parameters

were based off of the reconnaissance field and mapping data. For instance, discharge data was

estimated using average slopes for similar reaches (SMT-1, SMT-2, and SMT-4; Table 1) and the

maximum bankfull widths and depths described in the RGA/RSAT data.

The results of the empirical formula analysis provide a range of possible meander belt width values

that are suitable for the site (Table 5). For the main tributaries (SMT1,2, and 4), the meander belt

widths from the equations range from 14.2 to 22.1 m, with an average of 18 m. At SMT-3, the

formulas predict belt widths between 8.4 m and 17.6 m, with a mean of 12.3 m.

Table 5: Channel parameters used in the empirical formula and summary of results.

Channel Parameters (Inputs) SMT 1 / SMT 2 / SMT 4 SMT 3

Bankfull Cross-Sectional Area (m2) 1 0.345

Watershed Area (km2) 1.5 0.6

Bankfull Discharge (m3/s) 1.1 0.3

Slope (%) 0.005 0.005

Bankfull Width (m) 2.5 2.3

Bankfull Mean Depth (m) 0.4 0.15

bankfull maximum depth (m) 0.5 0.3

Meander Belt Calculations SMT 1 / SMT 2 / SMT 4 SMT 3

Source Equation Meander Belt Width (m) Meander Belt Width (m)

Collinson (1978) - maximum depth (m) 65.6D 1.57 22.1 9.9

Lorenz et al. (1985) - width (m) 7.53W 1.01 19.0 17.5

Williams (1986)- width (m) 4.3W 1.12 12.0 10.9Williams (1986)- channel area (m) 18A c

0.65 18.0 9.0

Parish/TRCA (2004) - discharge and drainage area 8.32*ln(9806*A w *Q bf *S)-14.83 21.7 8.4

Ward (2002)- width (ft) - no factor of safety 4.8W 1.08 14.2 13.0

Ward (2002)- width (ft) - w/ factor of safety 6W 1.12 19.3 17.6

Averages 18.0 12.3



7.1.3 Planform Analysis versus Empirical Formulas At this particular study site, the meander belt widths calculated using the Leopold and Wolman

(1960) method were deemed the most appropriate, as opposed to the formula approach. The

planimetric analysis is founded on relatively good data based on actual site conditions; they fall

within the range of belt widths estimated by the empirical formulas (which were based on maximum

channel parameter estimates), and yet they are still towards the higher end of the range providing a

level of conservatism; and finally, the historic data suggest, despite the intensive land use, these

channels have exhibited a relatively consistent planform over the 32 years covered by the air photos.

However, the revised belt width values are higher than the belt widths defined for this area in the

November 2009 study, in part due to the use of additional historic data, a shift to GIS-based

evaluation, which provides a better mechanism for scaling the photographs, and the use of

additional tools, such as the empirical equations (Williams, 1986; Ward, 2002; PARISH Geomorphic

Ltd., 2004).

Table 6: Summary of Meander Belt Width Results.

Reach

Preliminary MBW (m)

Erosion Setback (m) – 10% of Preliminary

Final MBW (m)

SMT-1a 18 1.8 22

SMT-1b 16 1.6 19

SMT-1c 12 1.2 15

SMT-2 18 1.8 22

SMT-3Hist 14 1.4 17

SMT-4 16 1.6 19

SMT-5 24 2.4 29



7.2 EROSION SETBACK From a geomorphic perspective, the 100-year migration rate typically represents the erosion setback

applied to either side of the meander belt to account for bank erosion and channel migration over

time. In the case of the study area tributaries, however, migration rates were difficult to estimate due

scale issues, distortions within the images, and the difficulty of locating an exact channel position

along short sections of the 2004 and 1978 photos. Therefore, a factor of safety of 10% for each

bank (total factor of safety = 20%) was added to the preliminary meander belt width. This

dimension essentially represents the hazard limits associated with stream erosion within the study

area. The erosion setbacks and final belt width dimensions are presented in Table 6. Additionally,

the final Meander belts can be compared to the Ward (2002) equation that includes a factor of safety

– the SMT 1, 2, and 4 values are all greater than the value provided by Ward, and the value for

SMT-3H is close to the Ward value, and easily within the error. Figures 6-9 exhibit the preliminary

and final belt width delineations for SMT-1, -2, -3, and -4.

Sixteen Mile Creek Tributaries Addendum – Recommended Structure Span January 2012


2.

Fig

ure

7: P

relim

inar

y an

d fin

al m

eand

er b

elt w

idth

deli

neat

ion

for r

each

SM

T-2.



Fig

ure

8: P

relim

inar

y an

d fin

al m

eand

er b

elt w

idth

deli

neat

ion

for r

each

SM

T-4.

and

SM

T-1b

.



Figure 9: Preliminary and final meander belt width delineation for Reaches SMT-1a and SMT-3.



8.0 CONCLUSION The Catholic Cemeteries of the Diocese of Hamilton plans to implement a new cemetery on

the 103 acre property located on the northwest quadrant of the intersection of Bronte Road

and Lower Baseline Road, in Milton, On. Conservation Halton requested that a meander

belt width assessment for four Sixteen Mile Creek tributaries (SMT-1, SMT-2, SMT-2, and

SMT-4) to ensure the proposed land use planning does not fall within erosion prone areas as

detailed in Ontario Provincial Policy Statement 3.1.1.

Field work and a historical aerial photograph assessment indicated the study area channels

are relatively stable, with some erosion located downstream of the SMT-4 and SMT-1

confluence, and just upstream of the Bronte Rd. crossing. Results of the geomorphic

assessment established preliminary meander belt widths of 18 m for SMT-2 and the lower

reach of SMT-1, and 16 m for SMT-1b and SMT-4. Final belt widths for these reaches were

22 m and 19 m, respectively. Reach SMT-3 actually comprised two separate channels, the

historic SMT-3 channel (SMT-3H) and a constructed channel to the southwest (SMT-3;

alternative channel). Field work found these channels to be poorly defined, and reach SMT-

3H was difficult to identify on air photos. However, initial meander belt widths were

assigned to these reaches, resulting in preliminary belt widths of 14 m for the historic

channel and 12 m for the alternate channel, and final widths of 17 and 14 m, respectively.



9.0 REFERENCES Collinson, J.D. 1978. Vertical sequence and body shape in alluvial sequences. In, Miall,

A.D., ed. Fluvial Sedimentology. Canadian Society of Petroleum Geologists. Memoirs 5: 577-586.

Galli, J., 1996. Rapid stream assessment technique, field methods. Metropolitan Washington

Council of Governments. 36 pp. Leopold, L.G. and M.G. Wolman. 1960. River meanders. Bulletin of the Geological Society

of America, 71: 769– 794. Lorenz, J.C., and D.M. Heinze. Determination of Widths of Meander-Belt Sandstone

Reservoirs from Vertical Downhole Data, Mesaverde Group, Piceance Creek Basin, Colorado. American Association of Petroleum Geologists Bulletin 69: 524-532.

Ministry of Natural Resources. 2001. Understanding Natural Hazards (Part 2), An introductory guide for public health and safety policies 3.1, provincial policy statement, Section 7.0 River and Stream Systems, Ontario, June 2001.

PARISH Geomorphic Ltd. 2002. Geomorphological protocols for subwatershed studies. Submitted to: Regional Municipality of Ottawa-Carleton.

PARISH Geomorphic Ltd. 2004. Belt Width Delineation Procedures. Submitted to: Toronto and Region Conservation Authority.

PARISH Geomorphic Ltd. 2006. Urban Stream Crossing Guidelines. Phase 2, Submitted to:

Toronto and Region Conservation Authority. Ward, A. D. Mecklenberg, J. Mathews, and D. Farver. 2002. Sizing Stream Setbacks to

Help Maintain Stream Stability. 2002 ASAE International Meeting, Chicago, IL. July 28-21, 2002. Paper Number 0222239.

Willams, G.P. 1986. River meanders and channel size. Journal of Hydrology 88.1: 147-

164.



10.0 ADDENDUM – RECOMMENDED STRUCTURE SPAN A risk-based approach is typically undertaken when evaluating the recommended span of a

crossing structure in terms of the local geomorphic conditions (Figure A-1). This risk

assessment protocol provides a site-specific context whereby an appropriate crossing

structure size can be evaluated and determined from a geomorphic perspective, based on the

processes that are operative at the proposed crossing location. Further integration of these

recommendations with design considerations and constraints identified through the overall

study will then establish whether the geomorphic requirements are the governing factor for

structure span. The risk assessment process involves the following parameters:

a) Channel Size: The potential for lateral channel movement and erosion tends to increase with stream size. Headwater streams tend to exhibit low rates of lateral migration due to the stabilizing influence of vegetation on the channel bed and banks. Erosive forces in larger watercourses tend to exceed the stabilizing properties of vegetation and result in higher migration rates.

b) Valley Setting: Watercourses with wide, flat floodplains and with low valley and channel slopes tend to migrate laterally across the floodplain over time. Watercourses that are confined in narrow, well defined valleys are less likely to erode laterally but are more susceptible to downcutting and channel widening, particularly where there are changes to upstream land use. Typically the classification of the valley will fall into one of three categories: confined; partially confined; and, unconfined.

c) Meander Belt Width: The meander belt width represents the maximum expression of the meander pattern within a channel reach. Therefore, this width/corridor, covers the lateral area where the channel could potentially occupy over time. This value has been used by regulatory agencies for corridor delineation associated with natural hazards and the meander belt width is typically of a similar dimension to the regulatory floodplain. The use of the meander belt width for structure sizing has been a criterion from some of the agencies and certainly represents a very conservative approach.

d) Meander Amplitude: The meander amplitude and wavelength are important parameters to ensure that channel processes and functions can be maintained within the crossing. For the purposes of this study, the meander amplitude of the watercourse was measured in vicinity of the crossing and used as a guide to determine the preliminary crossing structure span.

e) Rapid Geomorphic Assessment (RGA) Score: An RGA score is essentially a measure of the stability of the channel. Channels that are unstable tend to be actively adjusting and thus more sensitive to the possible effects of the proposed crossing. Accordingly, there is more risk associated with unstable channels. While the actual RGA score will be



reported, there are three levels of stability: 0-0.20 is stable; 0.21 to 0.40 is moderately stable; >0.40 is unstable.

f) 100-year Migration Rates: Using historical aerial photographs, migration rates were quantified (where possible) for each crossing location. A higher migration rate indicates a more unstable system and higher geomorphic risk.

Essentially, it is a risk assessment where, based on the condition of the channel, migration

rates and trends, existing planform and valley configuration, an appropriate opening size

from a geomorphic perspective can be developed.

SMT-1

Based on the findings of the historic assessment, field evaluation, channel planform and

valley setting, the risk associated with a crossing structure along this reach was deemed low.

From a reach-based perspective, the channel was poorly defined with bankfull widths in the

range of 1-2 m, and highly controlled by vegetation. It displayed a straight planform due to

the low order nature of the stream, as well as historic land use practices. Given the altered

nature of the stream, a governing meander amplitude could not be applied to this section of

stream in order to establish the preliminary structure span from a geomorphic perspective.

Although the meander belt width stipulated an 18 m preliminary width consideration, the

scale and stable nature of the drainage feature provided justification to refine this dimension.

In order to maintain the geomorphic form and function of the existing channel, a 5 m span

was deemed appropriate. This dimension refers to a single-span culvert (preferably with an

open footing) that is oriented optimally (90 degrees) to the direction of flow. It also

represents a dimension equivalent to roughly three times the average bankfull width which

provides an additional factor of safety in order to account for any future channel planform

adjustment or widening due to shading effects within the structure. Table A-1 provides a

summary of the risk-based considerations and recommended crossing span for SMT-1.

Preliminary Meander

Belt Width

Erosion Setback (Risk)

Meander Amplitude

Bankfull Width

Valley Setting

RGA Score Crossing

Span

18 m 1.8 m (Low) NA 1-2 m Unconfined 0.10 In Regime (Aggradation) 5 m

Table A-1. Geomorphic parameters and recommended structure size for SMT-1.



Figure A-1. Geomorphic risk-based assessment protocol for span recommendations.



SMT-2

















Preliminary Meander

Belt Width


Meander Amplitude

Bankfull Width

Valley Setting

RGA Score Crossing

Span





SMT-4

















Preliminary Meander

Belt Width


Meander Amplitude

Bankfull Width

Valley Setting

RGA Score Crossing

Span





Two additional crossing sites are located on small tributary swales leading to SMT-4

and SMT-2, respectively. Due to their small watershed areas, these channels do not require

meander belt delineation, but it is assumed that the meander belt widths would be smaller

than those for the downstream system. Otherwise, the channels are similar to the others in

the study site – unconfined, straightened, grass dominated, and relatively stable. Bankfull

widths in these swales appear to be around 1 m. As such, the recommended crossing span

at both locations is 3 m. This dimension refers to a single-span culvert (preferably with an


represents a dimension equivalent to roughly four times the average bankfull width which


adjustment or widening due to shading effects within the structure.

SUMMARY

A risk-based geomorphic assessment was conducted on a reach basis to establish the

recommended crossing span for 5 crossings in the planned cemetery, from a geomorphic

perspective. Within the context of the meander belt width assessment, the low risk, low

energy, and stable nature of the reaches within the study area provided justification to refine

this dimension from the meander belt width, resulting in a recommended span of 5 m for

the three major crossings, and 3 m for 2 minor crossings at tributaries. The span widths

refer to single-span culverts oriented optimally to the direction of flow.



11.0 ADDENDUM – DIRECT RESPONSE TO COMMENTS Response to Conservation Halton comments from April 8, 2011. In a document dated April 8, 2011, Conservation Halton provided comments to the

Hamilton Diocese’s initial application submission and subsequently permit a proposed

cemetery and related ancillary uses on the subject property.

Conservation Halton’s review included specific comments on the original November, 2009,

meander belt width assessment prepared for the Diocese of Hamilton by Parish

Geomorphic, Ltd. Since the original submission, Parish Geomorphic has revised the

meander belt estimates based on additional data and updated methods. The report,

therefore, was rewritten to address these issues and present the revised results. Additionally,

the report attempts to respond to many of the issues raised by Conservation Halton in the

April 8, 2011, letter. Because the responses are somewhat scattered throughout the

updated report, this addendum was added to summarize Parish Geomorphic’s responses to

Conservation Halton’s specific questions and comments (page 5 in the April 8, 2011 letter).

With respect to the assessment completed to define the erosion hazard limit, Conservation

Halton staff offered the following comments (in italics):

i Based on notes from previous site visits (which indicated potential historic fill placement along the north

bank of SMT-I), and a review of Conservation Halton's historic air photos, it appears that the assessed

meander belt widths for SMT-1 and SMT-2 relate to channels that have been impacted by agricultural

practices. Please identify how these practices have been accounted for in the calculations. Given the high

potential for on-going site alteration, was the use of the empirical equation to calculate meander belt widths

considered? If this approach was considered and deemed to be inappropriate, please provide discussion

supporting this decision. Can any other approaches to calculating meander belt width be considered? Please

revise the report to provide meander belt width calculations (including any supporting documentation)

associated with all appropriate calculation methodologies in the report, along with discussion supporting how

the ultimate meander belt width was calculated for each reach.



Parish Geomorphic agrees that determining meander belt widths in small, straightened

agricultural drainages is problematic. It is hard to determine if the channel is on its way to

equilibrium or if it is just beginning to adjust back to some version of a “natural” state. In

part, this is why Parish includes a synoptic survey when performing a meander belt width

assessment (Section 6). If the survey suggests the channel is adjusting then a more

conservative approach would likely be used in our determination. However, the stability

indices indicated that the tributary channels were primarily in regime (RGA stability indices

< 0.2, Table 4, Section 6) and the sequential air photos depicted a relatively stable channel

without a lot of adjustment (erosion rates < .1m/yr, Table 5, Section 5). This situation is

not surprising for these channels, considering their size and the clayey material they flow

through.

Meander Belt Delineation for this site is discussed in Section 7 of the revised report. It has

been acknowledged that the meander belts provided in the November 9, 2009, report were

undersized, in part due to use of unscaled, or incorrectly scaled, photographs. This issue was

rectified (Section 7.1.1) and the resulting meander belt widths were compared to estimated

meander belt widths from 7 different empirical equations, including the TRCA/Parish

Geomorphic (2004) equation (Section 7.1.2). The results from the air photo analysis lie close

to the mean values provided by the empirical equations (Table 5 and Table 6, Section

7.1.3)). The final meander belt widths, including the erosion setbacks, fit the Ward (2002)

equation that incorporates a factor of safety. Additionally, most of the formula calculations

are based on maximum values from the field reconnaissance, resulting in conservative

values. And finally, it should be noted that the empirical equations were not meant to

provide exact numbers. They were often developed to suggest general relationships, or to

use as a last resort if data is not available. The equations are usually associated with high

standard deviations and developed for particular uses or study areas. They should be used to

support values derived from field measurements or from air photos and contour maps.



Table 5: Channel parameters used in the empirical formula and summary of results.

Channel Parameters (Inputs) SMT 1 / SMT 2 / SMT 4 SMT 3

Bankfull Cross-Sectional Area (m2) 1 0.345

Watershed Area (km2) 1.5 0.6

Bankfull Discharge (m3/s) 1.1 0.3

Slope (%) 0.005 0.005

Bankfull Width (m) 2.5 2.3

Bankfull Mean Depth (m) 0.4 0.15

bankfull maximum depth (m) 0.5 0.3

Meander Belt Calculations SMT 1 / SMT 2 / SMT 4 SMT 3

Source Equation Meander Belt Width (m) Meander Belt Width (m)

Collinson (1978) - maximum depth (m) 65.6D 1.57 22.1 9.9

Lorenz et al. (1985) - width (m) 7.53W 1.01 19.0 17.5

Williams (1986)- width (m) 4.3W 1.12 12.0 10.9Williams (1986)- channel area (m) 18A c

0.65 18.0 9.0

Parish/TRCA (2004) - discharge and drainage area 8.32*ln(9806*A w *Q bf *S)-14.83 21.7 8.4

Ward (2002)- width (ft) - no factor of safety 4.8W 1.08 14.2 13.0

Ward (2002)- width (ft) - w/ factor of safety 6W 1.12 19.3 17.6

Averages 18.0 12.3



Table 6: Summary of Meander Belt Width Results (Leopold and Wolman 1960).

Reach

Preliminary MBW (m)

Erosion Setback (m) – 10% of Preliminary

Final MBW (m)

SMT-1a 18 1.8 22

SMT-1b 16 1.6 19

SMT-1c 12 1.2 15

SMT-2 18 1.8 22

SMT-3Hist 14 1.4 17

SMT-4 16 1.6 19

SMT-5 24 2.4 29

ii Please provide a copy of all materials used for analysis, (including the 1972 air photo image), and indicate

the location of all elements considered in the analysis (i.e. for the 1972 photo, please show the location of the

visible meander bends considered in the analysis of lateral and downstream migration rates).

Section 4 and Section 5 discuss the historical analysis, including meander migration rates.

The air photos are depicted in Figures 1, 2, 3, and 4, and the channel centerlines are

compared in Figure 5. Additionally, Figures 7-9 also show channel positions over time,

but at a smaller scale. The measurements were conducted at all bends in the lower 100 m of

SMT-1 and SMT-2 and any obvious bend or offset in the other reaches. Most of the

observable change occurs in the downstream sections of SMT-1 and SMT-2. The rest of the

channels are relatively stable and meander offset is within the measurement error associated

with rectifying and digitizing channels.

iii For SMT-I, based on a 2009 orthophoto, staff noted a meander amplitude of approximately 9m

(corresponding to a belt width of approximately 20m) near the bend adjacent to the farmhouse. It appeared

that in this particular area, the channel was less impacted by agricultural practices and may have had an

opportunity to naturalize. Staff also reviewed a 1954 aerial photo, which demonstrated that downstream of

SMT-I between Regional Road #25 and the watercourse's crossing of Lower Base Line, the watercourse had



a defined meander belt width of approximately 40m. While at this point the downstream reach had a

contributing drainage area of approximately 250 ha, as opposed to SMT-1's contributing drainage area of

approximately 170ha upstream of the confluence with SMT-2, staff question whether this information could

be used for the calculation or confirmation of the meander belt width upstream. Please review and evaluate

both of these items and provide further discussion in the report.

SMT-5 is included in the revised report for comparison purposes. The reach has a meander

belt of around 30m, but it is not a good reach to use for a reference upstream. As noted in

the April 8, 2011, comments from Conservation Halton, the channel holds water from both

SMT-1 and SMT-2. It also appears to be in a more defined “valley” with a greater slope.

The combination of these factors likely leads to greater meandering in this system than what

would occur upsteam.

.iv Please provide an evaluation of the geomorphological implications of the proposed flow diversion swale to

SMT-2, including any mitigation measures that may be required

Conservation Halton's request for an evaluation of this nature was premised on the original

storm drainage design as set out in the Stormwater Management Report for the Proposed

Cemetery Developments at Regional Road 25 and Lower Baseline Road, Town of Milton,

prepared by AMEC Earth & Environmental, dated November 2010. That stormwater

management design proposed a diversion swale extending across the entire north lot line of

the proposed cemeteries in order to convey off-site drainage to SMT-2.

As a result of updated evaluation of site constraints by this Meander Belt Width Assessment

Report, the updated floodline delineation and staking of aquatic fish habitat, the Master

General Plan for the proposed cemeteries prepared by Grever & Ward, revised to January

13, 2012 extends the drainage features and headwater tributaries of SMT-2 and SMT-4 to the

north lot line of the proposed cemeteries, obviating the need for the previously proposed

diversion swale along the north lot line. Instead, local runoff between these drainage

features is expected to be managed by interceptor swales with subdrains. In consequence, a

geomorphological evaluation of flow diversion to SMT-2 is unnecessary



v. In regards to SMT-3, we note that although drainage to this feature has been re-routed, the development

plans ultimately call for drainage to be returned to the natural channel. A geomorphic assessment of the

erosion hazard associated with this feature is required.

SMT-3H, the historic watercourse, is included in the revised report.

vi A meander belt width assessment is also required for the southeasterly flowing tributary which confluences

with SMT-I approximately 200 m upstream of Regional Road #25.

This watercourse, SMT-4, is also included in the revised report.

vii As the Parish report is intended to define the erosion hazard limit associated with a natural channel, staff

require that the report be signed and sealed by a licensed professional geoscientist or engineer.

Documents

Sixteen Mile Creek Tributaries - Meander Belt Width Assessment · PDF file · 2013-05-09Sixteen Mile Creek Tributaries Meander Belt Width Assessment Status: Final Report Version: