How High’s the Water, Mama? EarthCache
Hidden : 6/15/2018
Difficulty:
1.5 out of 5
Terrain:
1.5 out of 5

Size: Size: other (other)

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Geocache Description:


WARNING: The coordinates are at the edge of the parking lot. Most of the year, there’s a small beach at the edge of the river; although people regularly walk on the beach, it can be dangerous and there’s no need to go onto the beach to make your observations. If you visit the area during the spring high water (May to June), use caution near the water.


PARKING: The Regional Park has ample parking, but if it's full or if you arrive during high water and the park is gated, you’ll also find parking on Tall Road, under the bridge. Simply walk up and over the dyke.


BACKGROUND AND HISTORY
You will visit Matsqui Regional Park, located under and near the Mission Bridge, and on the Matsqui portion of the Fraser River dyking system. The Trans Canada Trail also uses this dyke on its way through the Fraser Valley.

The Fraser River drains 232,300 square kms, nearly one third of the province of British Columbia. It rises on the western slope of the Rocky Mountains, near Mt. Robson, and 1,375 kms later discharges its waters into the Strait of Georgia, south of Vancouver. The Fraser is the longest river and also has the largest watershed of any river that’s wholly within the province. Besides this, it’s the tenth longest river in Canada. The Fraser breaks out of the mountains at the town of Hope (elevation 41 m) before it flows through the Fraser Valley to the ocean about 180 km downstream.

Historically, the lower Fraser River was prone to flooding; indeed, First Nation legends describe a devastating flood within historic times. It’s only since the last few years of the 19th century that attempts have been made to control the Fraser during the spring freshet.

Throughout history, the Fraser has been important to humans: as a highway and a source of food for the First Nations, as well as for early European settlement. Later it became a place to build towns and pulp mills. Besides this, some of the province’s richest farmland lies on its floodplain. Despite the Fraser River’s great size and great potential for hydroelectricity, only a few dams, on some tributaries, provide hydroelectric power. The Fraser itself has never been dammed for two reasons: Its high sediment levels would result in dams with short lifespans, and there’s a strong traditional opposition from fisheries and other environmental interests. The Fraser is a major source of the salmon fishery. The Fraser’s dirty-looking water isn’t due to human pollution; rather, it’s due to silts carried from glacial melt waters and from other erosion of the mountains throughout its basin.


HISTORIC FRESHET WATER LEVELS AT MISSION
The Mission gauge, across the river from where you’re standing operates seasonally, to record each year’s freshet levels; a few outstanding high levels are:
-- June 1894: 7.92 m. The highest recorded level. (This level wasn’t recorded, rather it was estimated by studying such things as high water marks).
-- June 1948: 7.61 m. The last major flood, when the river broke through the dykes in multiple places, including the Matsqui dyke.
-- 1950: 7.45 m, fourth highest recorded level.
-- 1972: 7.12 m.
-- 1997: 6.39 m.

Although the water levels at Mission weren’t exceptionally high in 2018, they were higher than normal due, in part, to each of the following events in the Fraser River basin:
-- Higher than normal snow pack the winter of 2017-18.
-- Cooler than normal temperatures in April preventing low-to-mid elevation snow melt.
-- Rapid warming in late April with record-setting temperatures causing significant snow melt.


FLOOD CONTROL
Hydroectric dams provide electricity, and they also control downstream water levels, preventing floods. Due to the relative lack of dams on the Fraser and its tributaries, the Fraser Valley’s floodplains are protected by about 600 kms of dykes. Besides this, 400 flood boxes and 100 pump stations drain the land behind the dykes. This earthcache only considers the dykes, in particular the 11.644 km long Matsqui Dyke. This dyke protects 5,000 hectares, including agricultural lands, Matsqui and Clayburn villages, First Nations land, Hwy 11, railways, communications, etc. You’re standing about half way between its eastern and western ends. A dyke breach similar to the 1894 flood would inundate Matsqui Prairie and result in a catastrophic, economic loss not only to Abbotsford, but also to the Province and the Nation. Matsqui Prairie would need up to four months to be drained and for businesses to return to normal, assuming a 2-months sustained freshet. (City of Abbotsford Council Report, March 9, 2015).


MATSQUI DYKE BASICS
Simply put, a dyke is an artificially built, thick wall that’s intended to stop water flooding onto very low-lying land from a river or the sea. Dykes can be constructed in several styles; the diagram below shows the style of the Matsqui dyke (not to scale), with a setback strip between the river and the dyke, and a water-side slope that’s less steep than the back-side slope. Note also that the setback has some trees and shorter vegetation, but large trees aren’t permitted to grow near the toe of the dyke or on the dyke itself. This permits unobstructed visibility for inspection, and prevents holes from being created in the dyke. Check the Matsqui dyke where you’re standing and you’ll see this to be the case. (“Environmental Guidelines. . .”.) You might want to take a walk up or down stream on the dyke to observe the dyke’s construction.



INTRODUCTION TO FRASER RIVER DYKE HISTORY
Before dyke construction was begun, the lower Fraser River flooded regularly, but with the development of the Fraser Valley, the flood of 1894, was particularly devastating. After the 1894 flood, a dyking system began to be constructed. Unfortunately the dykes weren’t adequately maintained and over time, they fell into disrepair, becoming overgrown with brush and trees. Some of the dykes weren’t even adequately built for the exceptional freshet of 1948, and the dykes failed in several places. Thus, the flood of 1948 was the second most disastrous flood in the Fraser Valley’s recorded history. There’s been some flooding since then but it’s been fairly localized and not nearly as extensive as in 1948. Today, the dykes are carefully watched, regularly assessed, and maintained to prevent even minor flooding.

During your walk along the dyke make observations regarding maintenance, such as keeping the trees in control, occasional mowing of the sides for weed control, etc. The surface is gravel, wide enough for a single lane road, and is good walking for any street shoe. Below the dyke, near the river, is also a good, all-season trail that’s often within the trees and is cool in the summer.


SPRING 2018 FRESHET
During my research for this earthcache, I visited the dyke at Matsqui Regional Park several times to make observations; below are photos from my trips to the Regional Park.

May 5, was my first visit. The water had risen and was lapping at the grasses at the top of the river bank, but was still within the bank.


May 15, the water continued to rise over the next 10 days, as is evidenced by its height on the bridge pier and by the flooded tree. Visible through the water is the gravel on the park’s roadway.


May 21, the water level peaked on this day and began to drop by the next day. This photo was taken from part way up the dyke’s slope and shows that the roadway, as well as the picnic area were flooded. The tree in the May 15 photo is one of the ones in the background of this photo.


June 14, the water had dropped to lower than it was on May 5, and would continue dropping in the next little while. A family of geese enjoys a swim near the river bank. Silt deposited by the flood waters is evident on the lawn near the bridge pier, and soil erosion caused by the retreating waters is also evident in the foreground. These features could be part of another earthcache


May 21, 2018: This photo includes the gauge beneath the bridge.


SPRING 2020 FRESHET
For photos of the 2020 freshet, scroll down through the Logged Visits to the Owner Maintenance, dated June 29, 2020.


RESOURCES
These contain more detailed information on the dyke, and include photos.

“Environmental Guidelines for Vegetation Management on Flood Protection Works to Protect Public Safety and the Environment.” www.env.gov.bc.ca/wsd/public_safety/flood/pdfs_word/env_gd_veg_man.pdf . 1999.

“Freshet Flooding & Fraser Valley Agriculture Evaluating Impacts & Options for Resilience.” www.bcagclimateaction.ca/wp/wp-content/media/FV02-Freshet-Flooding-Agriculture-Impacts-summary2017.pdf . 2016.

“Revised Design Flood Profile for Lower Fraser River.” www.ebbwater.ca/wp/wp-content/uploads/2013/06/McLeanMannerstromLyle2007.pdf . 2007.


TO LOG THIS EARTHCACHE
Include any photos with your log, but send me the answers to the questions via e-mail. Use the information I gathered in 2018, unless you visit the park in a year of higher water levels; in which case, you may use the day you visited in that year.

Note: The gauge is placed so that Zero is on the river bank, which is a bit above sea level; consequently, if you use your GPS to read elevations, your readings will be higher than the gauge’s levels.

1. I was able to visit the park within an hour or two of the river’s highest, 2018 water level. What, in metres, was the water level on the gauge under the bridge? (Note: The gauge is in metres.)

2. Use either of the following two scenarios: If you use the 2018 high water, was the dyke needed to protect Tall Road? Why or why not?
If you use a year other than 2018, was the dyke needed to protect Tall Road? Why or why not?

3. At the time the information sign was erected under the bridge, what percentage of BC’s population lived in the Fraser River Basin.

4. The sign also tells the reader that “dykes have been built to protect the areas from ________ to _________.” Fill in the two locations.

5. Optional: With your log, post a photo of the river and/or its dyke. If the water is high, your photo will likely include flooding into the parking lot and possibly in the picnic area. If you use a year other than 2018, you could also post a second photo of the gauge found under the bridge.

Enjoy your caching experience and keep safe near the river.


Congratulations MulderClan! on logging the first FTF. It sounds like you had a good time at the park.


How high’s the water, mama?
Five feet high and risin’
How high’s the water, papa?
She said it's five feet high and risin’

Well, the rails are washed out north of town
We gotta head for higher ground
We can’t come back till the water comes down,
Five feet high and risin’

Well, it’s five feet high and risin’

From “Five Feet High and Rising” by Johnny Cash

Additional Hints (Decrypt)

Jnyxvat qvfgnapr naq gvzr arrqrq ner nf zhpu nf lbh qrfver.

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)


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