The Mining and Lands Commissioner

In the matter of the Conservation Authorities Act

G.H. Ferguson, Q.C.
Mining and Lands Commissioner

Thursday, the 15th day of
September, 1988.

And in the matter of

An appeal against the refusal to issue permission to construct gabions and a twin pipe arch structure and place fill in Riverview Creek in the Township of Smith in the County of Peterborough.


Corporation of the city of Peterborough


The Otonabee Region Conservation Authority

R.J. Taylor, for the appellant.
G.W. Coros, for the respondent.

The appellant appealed to the Minister of Natural Resources from the refusal of the respondent to grant permission for the construction of gabions and a twin pipe arch structure and the placing of fill in Riverview Creek in the Township of Smith in the County of Peterborough. By Ontario Regulation 364/82 the power and duty of hearing and determining such appeals were assigned to the Mining and Lands Commissioner. The appeal was heard in Peterborough on October 5 and 6, 1987.

The subject matter of the appeal is a series of gabions placed in Riverview Creek, which is in effect the ditch along the west side of Water Street in the north part of the city in the area south of Carnegie Avenue, which area is on the westerly side of Water Street opposite the zoo and a walkway bridge constructed across the ditch at the easterly end of a walkway which is the extension easterly of Amundsen Avenue which walkway bridge is located approximately 2,200 feet southerly of Carnegie Avenue. Pursuant to its policy of providing sidewalks along its arterial streets, one of which is Water Street, the city, through some misunderstanding between the officials of the city and the respondent proceeded with the construction of the gabions and the arches in the creek without obtaining the permission of the respondent.

The creek provides the outlet drainage for an area in the Township of Smith containing approximately 1,500 acres. This drainage basin outlets in a watercourse under Carnegie Avenue and flows along the west side of Water Street. A short distance to the south of the site of the walkway the waters flow under Water Street through two sixty inch culverts which are smaller in size than the arches used in the walkway.

The houses in the subdivision lying westerly of Water Street front on streets within the subdivision and the rear of the lots abut Water Street. There is a considerable slope to Water Street on the lots in question. There is a significant grade in a southerly direction from Carnegie Avenue to the site in question.

Although the lots front on streets within the subdivisions approximately four or five of the owners have constructed wooden walkways from the rear of their lots across the creek to Water Street.

The walkway consists of two elliptical culverts measuring seventy-two by forty-four inches in diameter and eight feet in length. Concrete has been poured over the culverts filling in the spaces at the sides of and between the culverts. This concrete forms the walkway and a handrail with vertical metal posts has been erected on both sides of the walkway.

It is apparent from Exhibits 15, a photograph taken prior to completion of the walkway, and 17, a photograph after the completion of the walkway and from viewing the site that a considerable amount of earth had been removed from the easterly side of the ditch to enable the placing of the pipes.

Immediately to the north of the pipes gabions were placed along the easterly edge of the ditch for a distance of approximately 400 feet. In addition a short distance of gabion wall was constructed southerly of the walkway. It is apparent from the photographs and the view that two or three feet of the easterly bank of the ditch had been removed for the purpose of constructing the gabion walls which abutted the new sidewalk placed by the city. In addition a gabion wall was placed in the easterly side of the ditch commencing at a point approximately 1,000 feet northerly of the walkway and running northerly for several lots which are approximately 100 feet in width. Here again it was apparent that the gabion wall had been placed easterly of the natural bank of the ditch. The evidence of W.H. Charters, the engineer for the city, further confirms that a five foot part of the bank was removed in order that a three foot gabion could be placed. In addition to the gabion walls, filter cloth and backfill were installed.

Both parties called expert witnesses in respect of the effect of the walkway on the control of flooding. The appellant called S.A. Vokes, a professional engineer who has had eleven years of experience in water resource management in the private sector. The respondent called L.J. Benson, who was employed by the respondent and other conservation authorities in the field. Both experts agreed that with flows of 650 c.f.s. or greater the structure would have no effect on the velocities or the height of the flood.

There has been no flood plain mapping of the watershed in question. The engineers utilized different methods of assessing flows. In his assessment of the matter, Vokes determined the capacity of the culverts and adopted flows that were larger or smaller than that flow, making HEC-2 analyses in respect of such flows. On the other hand Benson, using the HYMO calculation determined that the flow of the regional flood according to the Timmins flood standard is 2,063 c.f.s. Using a text book entitled "Regional Flood Frequency Analysis for Ontario Streams" by Moin and Shaw (1985) she applied a series of factors and concluded that in the area the flows for the following return periods are:

Return Period Flowrate (cfs)
1:2 year 324
1:5 434
1:10 544
1:20 663
1:50 845
1:100 1000

In applying the HEC-2 formula different result were attained by the engineers which will be set out subsequently. There was no evidence to clearly indicate a reason for the difference in the results. Vokes suggested in cross-examination his calculations were most conservative as he had assumed in his calculations that a wall were erected along the westerly side of the ditch and that his calculations did not include the reductions in elevations that would have resulted from the utilization of the storage capacity lying to the west of that line. He also suggested that Benson's calculations may not have taken into consideration the enlargement of the channel as a result of the placement of the gabion walls with the result that her calculation of the situation prior to the installation of the walkway did not reflect the narrower width of the channel. In this regard there was filed as Exhibit 11 a cross section numbered 1212 showing the effect at the premises known as 1212 Cartier Boulevard which is the first house to the north of the walkway. An examination of that cross section only indicates one series of spot elevations although it shows two flood elevations. The tribunal is not satisfied that the calculations of this witness actually took into account the widening of the channel or the improvement of the flows resulting from the installation of the gabion walls.

Vokes made four calculations. Firstly he calculated the existing conditions prior to the construction of the walkway. His second calculation was related to the increase upstream of the walkway and he concluded that in the worst situation there would be an increase in elevations for a distance of ten feet upstream from the walkway. He examined flows of 100, 200, 350, 500 and 650 c.f.s. and concluded that in the range of 350 to 500 c.f.s. the flows were too large for the culverts and there would be overflows. In these flows he concluded that the depth of the additional flooding would be very local and the effect would have dispersed at the location ten feet upstream of the culverts.

Vokes also made a calculation assuming that both culverts were completely blocked. His evidence was that such a result would be most unlikely. In his opinion the size of the culverts and their locations were such that it was highly unlikely that both culverts would be blocked. He concluded that with full blockage there would be no increased water levels upstream during the high flows. In that regard he said,

As far as a full blockage which was simulated on our third and fourth runs it was found that flood levels, there were no increased water levels upstream during the high flow situation. In other words, when you have the larger flows and you completely block the culvert the watercourse itself would have been flowing full or possibly exceeding its banks anyway so the levels that we calculated as a result of high flows were not made worse by the fact that we had essentially put a dam or at least simulated blockage at the walkway. It was essentially made into a dam. We assumed no water could go through the culverts and that is the scenario that we are looking at there.

With reference to blockage at low flows the witness said,

We determined that water levels would be affected under the low flow. As I said earlier we did not feel there was a chance blockage could occur, but when we did model a complete blockage at the lower flows, that is when the water levels were increased upstream from normal because normally under low flows the water would not be exceeding the channel but if you were to dam it up completely at the culverts then that is why you end up with the higher levels for the low flows but not for the higher flows.

With reference to a complete blockage at the Water Street culverts the witness said,

This is Water Street, right here. The city sized the culverts at this location slightly larger than the pipes that drain Water Street. If we were analyzing blockage at this point we felt in fairness to the city we should look at what would happen if these had blocked anyway. Obviously if blockage could occur at these pipes, the smaller pipes here would be subjected to the same type of blockage, so when we considered full blockage at this point, that also resulted in a damming effect of water to a point upstream where the normal flow in the channel took over. So for both of those instances if you dammed up from the Water Street culverts to approximately 750 feet upstream of the crossing at which, sorry at Station 7 plus fifty, that is about 400 feet upstream of the walkway. The walkway is slightly higher at this location because Water Street slopes upstream as does the watercourse so it is slightly higher so that is why our analysis shows that a complete blockage at these culverts as opposed to Water Street does result in the damming in that the ponding of water for a slight distance of approximately 100 feet upstream further than damming at this point and that was worked out locally at a depth of eight inches and that would be the result.

With reference to the effect of such flooding the witness said,

The statement I made before about the eight inches that leads, that might lead a person to believe that flood depths are consistently increased by that depth but this increase of eight inches that is talked about it only occurs adjacent to the walkway crossing and as you proceed upstream obviously the difference between the two computer runs is less. Just as the placement of the walkway culverts resulted in approximately a five inch increase at that location, complete blockage of the culverts results in eight inches of additional flooding again compared to blockage at Water Street, but it is only very local to the walkway crossing itself. Now as I said it dissipates slightly after that.

With reference to flooding of the ditch above the site at which the walkway was constructed the witness said,

Q. Now in the terms of your analysis of this area of Water Street, could you identify any other areas along Water Street that would have the potential for flooding.

A. Yes at higher flows when examined the ditch or watercourse up the side of Water Street there were locations upstream, heading up toward Carnegie Avenue, in this location in which there are houses, where the watercourse in that area was smaller as in wider, sorry, narrower and shallower than points downstream so the water -- flood levels could leave the watercourse at this point and proceed down Water Street at a higher flow, I mean in the area of 500 to 650 c.f.s., again a higher flow.

With reference to a suggestion of the respondent made prior to the hearing of the appeal that an alternative design would be acceptable, particularly one in which no part of the walkway would be in the flood plain the witness said,

Q. But in the context of your own experience and expertise can you provide any commentary as it would pertain to alternative designs in regard to the walkway.

A. In an instance like this, obviously a free span type of walkway bridge, one that spans from top of bank to top of bank and extends upward, that would result in no obstructions to flow, until such a time that the water is already at the side of the banks but such a design when reviewed with the City of Peterborough for such a short distance over the creek would be such an exaggerated arch and it was so close to Water Street, it was pointed out to me that not only possible icing problems, people going out onto Water Street but the one of wheelchairs which I mentioned earlier.

Benson criticized Vokes' assessment of the situation on the basis that in her opinion he had not prepared sufficient cross sections or based his analysis on sufficient cross sections to meet the standards of the current requirements of the Ministry of Natural Resources in respect of flood plain mapping. It is apparent to the tribunal that if the analysis was such that at one cross section it was established that the effect did not extend to the next upstream desirable cross section it is pointless to measure additional cross sections. In her assessment of the matter Benson created a cross section at each of the properties lying to the north of the walkway and for a distance downstream of five properties, the most southerly of which is opposite the culverts under Water Street, making a total of fourteen cross sections. She calculated elevations for the flows at each cross section. She examined flows of 100, 200, 350, 500 and 650. She also purported to calculate the pre-existing situation, the situation with the walkway installed, the situation with a blockage at Water Street and the situation with a blockage at the walkway. A detailed and extensive table showing the results of her HYMO and HEC-2 calculations is contained in her written report filed as Exhibit 9.

It will be noted at the outset that Benson made no calculations for flows above 650 c.f.s. which, as indicated above, she concluded represent the one in twenty year storm and her concurrence with Vokes' opinion that the effect of the walkway terminated in floods of that flow or less frequent floods.

Benson's conclusions in respect of her analysis were generally discussed in Exhibit 9 under the heading "Discussion of Results" as follows:

The installation of the bridge will cause an increased depth of flooding on private property by as much as 1.44 ft. in the presence of unblocked conditions at 650 cfs. Some degree of increase occurs on four private properties at that flow rate, and the top width of the floodplain increases by as much as 41 ft.

It is not unlikely that debris during a high flow will cause culverts to become blocked especially since there are several small private crossings upstream which could easily destruct and flow downstream. A comparison was done between water levels resulting from a blockage at Water Street vs a blockage at the walkway. A blockage at the walkway will cause increased flooding further upstream (than if the blockage occurred at Water Street) by as much as 0.31 ft. at 650 cfs and will effect as many as twelve private properties throughout a range of flows. Some of these properties will experience flooding for the first time at that flowrate.

Regarding her detailed analysis it is noted that with respect to the five downstream properties there was no indication of flooding on the private properties without a blockage except in the event of the property immediately to the south of the walkway in which case she calculated that there would be one-tenth of a foot of flooding in the event of a 650 c.f.s. flow. It must be remembered that at this location there was a considerable widening of the channel and the insertion of gabion walls.

Benson showed some interesting results in respect of blockages at Water Street and at the walkway. With reference to the property adjacent or somewhat to the south of the culverts through Water Street she showed a significant increase in flooding with a blockage at Water Street as contrasted with a blockage at the bridge. In the event of a 100 c.f.s. flow, she showed an increase of approximately five feet of flooding at Water Street. At 650 c.f.s. the difference in elevations is 1.59 feet. This would tend to confirm the position of the appellant that the opportunity for flow through the walkway is equal to if not greater than the flow through the culverts under Water Street. However it must be remembered that there is a drop of elevation in this area between the walkway and the culverts under Water Street, which area measures four or five hundred feet. This difference in elevation is reflected in her calculation in respect of the property immediately to the south of the walkway where she shows an increase in elevation of 1.72 feet with a blockage at Water Street and an increase of .36 feet with a blockage at the walkway in respect of flows of 650 c.f.s.

More importantly regard should be had to the calculations above the walkway. Benson concluded that at the first property above the walkway in flows of 100 c.f.s. there would be an increase in elevation of .58 feet with the installation of the walkway, which increase would not result in any flooding on private land. She also calculated for similar flows an increase of 2.21 feet with a blockage at Water Street and an increase of 1.67 feet with a blockage at the walkway. Similarly in a 650 c.f.s. flow she calculated an increase in height of 1.44 feet which would create, as noted above, flooding for a distance of 41 feet onto the property. Here again she also showed increases of 1.34 and 1.11 feet in connection with the respective blockages.

In passing, it is also interesting to note in respect of the flow of 650 c.f.s. that her calculations showed an elevation of 103.87 feet in the pre-existing situation which is an elevation of 1.6 feet above the 200 c.f.s. flow which was said to result in an increase in flooding on private property of .26 feet. Although this comparison contains no proof as to the amount of actual flooding it certainly indicates that in the natural condition there is a significant amount of flooding on this particular property at 650 c.f.s.

At the second property the calculations of the witness showed no increased effect on the second property with 100 c.f.s. and 200 c.f.s. flows. She showed an increase of .44 feet at 350 c.f.s., .98 feet at 500 c.f.s. and 1.27 feet at 650 c.f.s.

On the third property the only effects shown were an increase in elevations of .03 feet in a 500 c.f.s. flow and .24 feet in a 650 c.f.s. flow. At the more northerly properties she showed no increase in depth of flooding on the private properties.

It is significant that this witness showed figures indicating an increase in the level of flooding on Water Street. These increases ranged from 1.44 feet to .01 feet. Unfortunately we have no evidence to show the depth of flooding that was being increased by these measurements and cannot make any conclusions as to the significance of the increase of such flooding.

In her concluding part of her report the witness dealt with discussion of damages. Her first conclusion was that the presence of the walkway would create a funnelling effect and an increase in velocity with its risk of increased erosion and scouring downstream as a result of the "funnelling" through a smaller opening. The tribunal cannot conclude that the openings in the walkway are smaller than the previous channel and cannot concur in this result.

Secondly, the witness concluded that there was decreased velocity upstream resulting from the structure and increased flooding with additional opportunities for the deposit of sediment and other debris. The tribunal is more inclined to accept the evidence of Vokes in this regard. As indicated above the tribunal would have no difficulty with this conclusion if it could have been satisfied that the calculations had been based on a proper measurement of the pre-existing channel.

Thirdly, the witness submitted that there would be increased flooding in the backyards of the properties along the westerly side of Water Street. In her words "in other words, a backyard which previously began to flood at a level associated with the flow rate of 650 c.f.s. may now begin to flood at a level associated with a more frequent flow rate of, perhaps, 550 c.f.s." Again this conclusion is dependent on the basic assumption of the capacity of the pre-existing channel.

Fourthly, the witness pointed out that increased flooding would affect one garden shed and fences along the west limit of Water Street and flooding on Water Street itself.

Fifthly, the witness referred to the risk of personal injury or drowning to members of the public who might be attracted to the walkway. In this regard the evidence indicated that individuals or the public are presently using wooden walkways or bridges that are not fastened and which, according to the photographs produced by the respondent, float or turn on their side in photographed flooding situations and the tribunal would have considerable difficulty in determining that the substantial walkway constructed by the city would be a greater hazard than the existing walkways. It would seem to the tribunal that there would be far greater risk in falling off an existing structure or causing an existing structure to ultimately break loose during use than the risk associated with the walkway. The tribunal appreciates that the witness was also referring to the attraction of children who might be affected by the increase in the depth of flooding. Again the increase in the depth of flooding is a matter which this tribunal is not prepared to accept and the tribunal does not feel that this allegation should be seriously considered.

Benson also gave evidence as to the policy of the respondent in respect of exceptions based on the principle of overriding municipal, provincial and federal interest. With reference to municipal footpaths the policy is contained on p. 15 of a document entitled "Flood Plain Management Policies", revised March 12, 1987 a copy of which was filed as Exhibit 14. The relevant provisions read,

  1. It is recognized that certain utilities or services such as storm and sanitary sewers, natural gas or oil pipelines, hydro corridors, footpaths and transportation links will, from time to time, be required to cross or use the flood plain. Such uses should not impede flood flows or be located in such a manner as to cause adverse effects to the flood plain upstream or downstream.

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

    1. As much as possible, bridge or structural abutment should be located outside of the flood plain to minimize obstruction to water flow.
    2. Where structures are necessary within the flood plain the structure should be designed so that overtopping or flanking can occur with a minimum of damage to structure or the channel walls. Major bridges not designed for the Regional Flood should have their approach ramp(s) designed as spillways. Smaller footbridges should be designed to withstand blockage and allow for spill.
  2. Stage-storage characteristics of the flood plain should be retained.

The submissions were that the proposal did not fall within this policy as the abutments were not placed outside of the flood plain and as there was a reduced allowance for spill. The tribunal is satisfied on the agreement of the parties that there is no serious obstruction to the flows of a regional storm by the walkway or flows ranging from those of a regional storm, 2,063 c.f.s. to flows of 650 c.f.s.

Related to the same issue it was suggested as a second alternative that the footbridge was unnecessary at the location at which it was installed and should have been located at a location some distance to the south. The tribunal is satisfied that the public user in the area indicates that this proposal, while it might have evaded the issues brought before this tribunal, is not consistent with the existing public use of the right-of-way of Water Street.

Basically the submissions of counsel related to the conflict in the evidence, the obligation of the municipality to provide adequate roadways and the absence of viable alternatives. The argument of counsel for the respondent related to the risks resulting from the increased flooding illustrated by the evidence of its witness and the risk of lawsuits in accordance with the principles of the case of Scarborough Golf & Country Club v. City of Scarborough et al. 55 O.R. 2d 193. Included in the risks were the alleged increased flooding of private property and also of Water Street which would interfere with the operation of fire and other rescue vehicles in an emergency and would require extensive detours in such situations.

In the opinion of the tribunal the appeal should be allowed for the following reasons:

  1. There has been an expenditure of public funds on a now existing structure and the removal of such structure would constitute a waste of public funds.
  2. The tribunal is not satisfied as indicated above on the evidence that the increase in flooding is of the extent alleged by the respondent. Further the issue of increased flooding affecting fire and rescue vehicles should be regarded in the light of the evidence agreed to by the parties that there is no effect from the walkway in flows in excess of 650 c.f.s. and the evidence of the respondent that such increase would commence with flows of 500 c.f.s. at the third property above the walkway and that such increases were estimated at .01 feet for 500 c.f.s. and .08 feet at 650 c.f.s. These amounts are less than one inch. The largest estimate was .31 feet, 3.6 inches, at the fourteenth property above the walkway at flows of 650 c.f.s. At this property, No. 1268 Cartier Boulevard, there was said to be no increase in the height of the flooding created by the walkway at any of the considered flows.

    This situation is confirmed by the evidence of Vokes particularly that the result will occur with flows between 500 and 650 c.f.s. There was no evidence of the depth of flooding on Water Street without the walkway in such flows. The engineering evidence noted the increase but did not provide any evidence of the flooding of Water Street at such flows without the increase from the walkway. It may well be that traffic would be diverted in such circumstances even without the increase from the walkway. The tribunal cannot conclude that this narrow bond of flows should govern the entire situation.

  3. The tribunal is satisfied that there is no reasonable alternative to the proposal and that the proposal should be justified on the basis of overriding municipal concern.
  4. The tribunal is satisfied that the walkway is a significant improvement over the existing systems of unauthorized wooden bridges and that such wooden bridges are a serious hazard to the control of flooding as they are unattached and very easily could cause a blockage of the Water Street culverts in the pre-existing situation.
  5. The tribunal is satisfied that there is no significant increase in elevations and that the increased attractiveness to children in the area cannot provide a reason for the removal of the structure.
  6. With respect to legal liability the tribunal has considerable doubt that any significant increase in flooding could be established and the areas that are subject to such property damage are not significant.
  7. The respondent will be able, having regard to the ultimate decision in the Scarborough Golf & Country Club case to make its own determination as to whether it wishes to have the walkway remain.
  1. This tribunal orders that the appeal is allowed and permission is hereby granted, in so far as retroactive permission may be granted, to the construction of the walkway crossing Riverview Creek as of the date of hearing. It is understood as a condition of this permission that the appellant will take all reasonable steps to cause the illegal and unauthorized wooden bridges crossing Riverview Creek to be removed.
  2. This tribunal orders that no costs shall be payable by either party to the matter.

Signed this 15th day of September, 1988.

Original signed by G.H. Ferguson
Mining and Lands Commissioner.