Rain and Flooding

Blue Jay Barrens is about as wet as it can get.  A long sequence of storms moving through during the past week has dropped nearly six inches of rain over the area.  Storm clouds moved through once or twice every day.

The soil, already fully hydrated by over six inches of rain in March, quickly became saturated and the output of each storm had nowhere to go but to run overland to the creek.  A storm yesterday afternoon produced 0.8 inches of rain in 15 minutes.  The result was a flash flood, the third this week.

Water from the township road carried red clay particles to the pond.  It looks like a bowl full of mud, but the water clarity is not as bad as it appears.

A closer examination shows the water to still be fairly clear.  The clay tint makes the dark Wood Frog tadpoles easy to see. 

The tadpoles have just recently taken on the traditional tadpole shape and become free swimming.  If these rains persist, there will be no problem of the pond drying up before the tadpoles transform into little hoppers.

The diversions around the vegetable garden have been working overtime this spring.  The garden sits in a level area that was formed by eroded soil being trapped by an elevated roadway.  Without the diversions, water would inundate the garden after every rain.

After each storm, I check to see that the female Carolina Wolf Spider is alive and well.  So far, she seems to have been unaffected by even the heaviest of rains.

Small upland waterways swell to wide streams as the water quickly rushes downhill.  After each rain event, I try to get down to the creek to see how the increased water flow moves through the channel.

The quickest way to the creek is over the hill.  Even in the driest, most well drained locations, water still stands on the surface.

Five minutes after the rain has stopped, concentrated water flow is still pouring from small woodland watersheds along the creek. 

Water running from these woodland areas is generally clear, but it carries a heavy load of leaves.  The result is a mosaic of bare ground and thick piles of leaves.  This will influence the pattern of plant growth through the rest of the year.

I’m always relieved when I see the bridges still intact.  All but one of the bridges have been replaced to an elevation above the record flood level.  If we do get a flood capable of tearing out this bridge, I hope I’m here to see it, because it will be a truly rare and terrifying event.

Calm and scenic features, such as a small waterfall, are covered over by the flood.  It’s always a surprise when the water drops and the creek resumes its earlier appearance. 

Water pools in the flood plains as it waits for a chance to seep into the ground.  This soil is very well drained and normally allows rapid water infiltration.  Its appearance now makes you think of vernal pools and amphibian breeding, but given a day without more rain, it will pass all of this water into the creek.

This is the last bridge needing to be repaired and elevated.  It has been moved and battered by flood water many times over the years.

Downstream of the bridge is the area blocked by a log jam a couple of years ago.  Since the removal of the jam, water now flows freely through the channel.

Since I wait for the lightning to clear the area before venturing out after a storm, I usually miss seeing the water at its highest level.  At the peak of the flood, water left the creek channel and moved overland.  This area was scoured clean when the water was suddenly blocked by the formation of a log jam and forced out here.  It’s likely that a new channel will be formed here someday.  I could have left the log jam in place and let the new channel form, but this little area has a nice collection of woodland flowers that I would like to enjoy for a while longer.

The third of three large bridges is now well above flood level.  This bridge was repaired using sections of decking from two older bridges.  I think this one is elevated and anchored well enough to withstand any flood.

I find still photos of rapidly moving water to be lacking in impact, so I have included a short video that captures the movement and sound of the angry creek.  It is also available for viewing on YouTube by clicking HERE.

Flood Damage - Bridges

I think the term flood damage is most appropriately applied to the effects on artificial structures that have been intentionally placed in the path of rapidly moving water.  The only structures I’m concerned with are the foot bridges along the trails.  This bridge crossed the tributary I followed to the creek.  I was not surprised to find it a bit out of place.

This bridge acted just as it was designed to do.  One upstream corner of the bridge is cabled to an immovable tree.  When the water rises high enough to float the bridge, the entire structure is pushed out of the current and on to the bank.  It’s a fairly easy operation to lever the bridge back into its proper place.  Each time a bridge is replaced, I elevate it to a point just above the new high water mark.  I keep thinking that we’re unlikely to have a higher flood and the new elevation should mean never again having to reset the bridges, but I’m continually proven wrong.  The storm of 1997 that produced seven inches of rain in 24 hours, was said to be an event likely to occur only once every few hundred years.  I thought that bridges set above that level would be pretty safe, but that record has been broken seven times since then.  The storm that caused this latest flood only produced 1.2 inches of rain, but it fell on already saturated ground within a period of just a few minutes.

This bridge didn’t get washed away, but it also didn’t fare very well in the flood.  When I first saw it, the image reminded me of a giant snake skeleton strung out on the creek bank.

As water from the creek forced the bridge onto the bank, runoff from the hillside tried to push it back toward the creek.

I once tied to a jetty on the north side of Pelee Island that looked much like the remains of the bridge.  This bridge will not be swinging back into place any time soon.

At some point in the action, the bridge support attached to the cable snapped in two.  Fortunately, the bridge had moved far enough over the bank to be caught and held in place only a few feet away.  I’ll have to get out and salvage the deck boards before we have an even bigger flood that carries away the entire structure.

The ruined bridge seems to blend harmoniously with the torn up surroundings.  I’m afraid it will look totally out of place once things green up this spring.  I’ll make it a priority to get all of the bridge parts picked up before the spring wildflowers begin to bloom.

Bridge Back in Place

The early flowers have pretty much reached the end of their blooming season, so it’s about time for me to mow the trails. In preparation for that event, I’ve been putting the bridges back into position. They may look a little bit battered, but they’re still sound.

Presence of the bridge on the bank suppressed the plant growth. Now that the bridge has been removed, the plants will be quick to grow.

Boards provide a smooth surface on which the bridge supports can slide as I pull the bridge back into place. They also act as levers for scooting the bridge into its final position. I loop a rope around the bridge supports and use it as a handle to pull the bridge along. The bridge can be popped back into place in a short amount of time with very few tools.

This gravel bar was created by the same floods that moved the bridges. A temporary blockage just downstream slowed the water at this point and caused the heavy particles to drop out. The loose packed sand and gravel didn’t provide much support. It reminded me a lot of playing at the beach, at least the kind of beach people who live inland are used to. With the blockage removed, normal winter runoff will have all of this gravel moved away by next summer.

A few rains will get the deck cleaned off. We’ve moved into a drier pattern now and the scattered showers have been consistently missing us. It may take a while before cleansing rains show up.

The section of runaway bridge deck has been pulled from the brush pile and is ready to be hauled back upstream. The last bridge won’t be back in place for a while. One of the bridge supports, an eleven inch diameter cedar log, suffered a green stick fracture when it got tangled in other debris and hit a tree. Fortunately, I can use one section of bridge deck as a temporary way to get DR across the creek when I mow.

Bridges vs Floods Round 2

Weather related records are being broken at a rapid pace this year. Some of the records stand for only a short time before they are again broken. Setting a record should be a positive experience, but I’ve not experienced much joy in these record breaking events. A recent intensive storm has set a new high flood level that will be very difficult to top. Foot Bridges that survived the previous record flood just last month were torn to pieces by the wild water that accompanied this last event. Evidence of this flood is going to be visible for a long time.

The only sure way to avoid flood damage is to stay out of places that flood. If you do put something in the path of the flood, expect it to be damaged. I’ve always known that any of my bridges could be torn apart by a wild flood. In anticipation of that fact, I designed the bridges so that the resulting pieces were predetermined. Although this six foot section of bridge decking is 600 feet downstream of its original position, it has not received any damage. It is intended to be one of several separate units that can be easily carried back and reassembled in the proper location.

Here’s the rest of the bridge decking, tethered by its safety cable. The logs used as bridge supports are in a tangle of debris downstream. Moving water is a powerful force, but that shouldn’t have been enough to demolish this bridge. Some logs showing in the debris tangle came from a neighboring property somewhere upstream of the bridge site. These logs, carried down the channel by the flood water, would act as battering ram and would have hit the bridge with enough force to take it apart. Had the water been free of debris, the entire bridge would have been sitting comfortably on the far bank as has occurred in the past.

When I constructed foot bridges across the creek, I had to decide just how much damage I was willing to accept and how much I was willing to deviate from my vision of the perfect crossing in order to reduce damage. As a child, one of my greatest joys was peering through the boards of a bridge deck and spying on the aquatic life beneath. My preference would be to have low bridges that provide an intimate nearness to the creek, but this type of bridge would move with every high water. Raising the bridges high enough to avoid any flood impact would result in a much longer span across the creek and a bridge deck far removed from the water. I chose a position in the middle and set the bridges so they would only be damaged by exceptional runoff events which would be expected once every five to ten years. This bridge was moved from its stone supports, but wasn’t really damaged. The path of bright green ground cover indicates the area that was swept clean by the flood.

The bridges will be repositioned when things dry out. I’ll mark the new high water levels and see if any adjustments to the bridge heights can be accomplished to make them a little more secure. I don’t want to get them too high, because there’s always the chance that I’ll fall off of one some day.

Bridges vs. Floods

There hasn’t been any snow for awhile, but we’re far from getting any relief from the weather. Now we’re in a pattern of rain storms coming through every few days. Saturday’s storm dumped 3.4 inches of rain on top of already saturated soils and the resulting flash flood rose to set a new record. One of my concerns during times such as these is the security of my foot bridges spanning the creek.

After the record setting floods of 1997, this bridge was relocated and elevated to keep the bridge deck above the high water mark. The accumulation of debris shows that the bridge was submerged for at least part of the recent flood event. Fortunately, the flood water wasn’t strong enough to move it from this position.

This bridge didn’t fare quite as well. It looks a mess, but things aren’t really as bad as they appear.

The bridges are intended to move with the flood water. Each bridge is tethered to an immovable object. When the water rises, the bridges float up and lay themselves along the bank. The restraining cable can be seen attached to the lower right-hand corner of this bridge. Repositioning the bridge is much easier when it’s still at its proper site rather than a quarter mile down the creek.

My options in a situation like this are to either let the bridge move during a severe flood or elevate it above the high water level. Elevated bridges make it difficult to cross with DR Brush and still require maintenance of the approaches after a flood. Anchoring the bridge in place doesn’t work because the immobile bridge causes the creation of plunge pools, bank erosion and channel redirection such as you would get when a tree falls across the channel. Bridge movement is a rare occasion, so it’s not something I have to deal with very often.

At its peak, the flood water completely covered the level ground between the hills. The leaves that weren’t washed away, ended up plastered on the bases of the tree trunks. It’ll take a little while for the plants to upright themselves.

This bridge on a smaller tributary is intended to stay in place. The rock bottom of the stream is immune to plunge pool development and rock in the banks makes the whole site fairly stable. Strong storms are predicted through the middle of the week, so the bridges may get hit again. I’ll wait until things dry up a bit before putting things back where they belong.