Riverine sediment consistently changes seascape

Creeks and rivers carry a sediment load into the ocean.

Ordinarily, talking about the weather is considered a topic for idle small talk, a stopgap solution for when we know nothing else to say to each other.

Not so this week: There is nothing idle or evasive when people talk about the weather. Perhaps the last decade of climate change has gotten us used to climate-related extremes, record-breaking temperatures and even weather-related disasters.

This week, the whole Pacific Northwest coastline is sweltering in a heat wave predicted to reach temperatures above any recorded. Officials are releasing warnings to stay cool, drink water, limit activities and watch out for each other.

I know it is difficult to imagine the heat wave for us here in Kodiak, where the creeks and ponds are still overflowing with extremely high water levels from the past week’s rainfall, hiking trails have turned into water runoffs and unpaved roads are riddled with new water-filled potholes.

Riding my bike this morning, I was so cold that I wished I had gloves to protect my hands. I’ll take those cold hands any day over a heat wave, and I feel truly sorry for everyone trapped in the infernal heat.

Such is the nature of extreme weather events that in one area the thermometer climbs, whereas in another area flood warnings are issued. For Juneau, Kupreanof Island and Lynn Canal NOAA has issued high-water and flood warnings because high temperatures have melted a lot of the winter snow still present at high latitudes, which now flows down in creeks and rivers toward the ocean.

Coastal oceanographers can detect a drop in salinity when high-water events like this flush large amounts of fresh water into the ocean.

The rivers also carry a load of sediment with them, the consistency and amount of which depends on the geography and geology of the area.

If you notice a little creek usually just trickling down the side of Pillar Mountain, which has swelled to a sizable waterfall during the last two weeks, that increase in water volume and energy washes down the soft top layers of soil.

Sometimes the sediment carried by the rivers can be seen as a distinctly different-colored plume when it reaches the salty water of the coastal ocean.

Most of us wonder about this only for a moment. Once it is in the ocean, we consider this sediment washed “away.”

“Away” is a curious word: Most people use it as an end destination, like the end of existence, as if something magically dissolved into nothing.

The dictionary is not so dilutional about it; it defines the word as (1) at a distance, and (2) in a place of storage or safekeeping. If we started to think about “throwing things away” in those terms, perhaps we would be more careful with the end-of-life storage of the things we produce. 

Just like the things in your roll cart do not suddenly disappear from existence when the garbage truck picks them up, the sediment that washes into the ocean also does not disappear.

Once the directional flow of the creek or river that carried the sediment into the ocean ceases, the sediment load will sink to the bottom and get deposited.

Often, the energy of tides and storms will work and rework the sediments, carry them on and deposit them again and again, forming slopes, bars, hills, valleys and sandflats underwater. Most continental slopes also feature a sedimentary wedge, basically the side of a hill.

Not only do these sediments change the very substance of the underwater scenery, but they also contain the minerals and salts of the rocks they once were and contribute to the salinity of the ocean and its chemical composition.

Some rivers carry large amounts of pollution into the one world ocean. For the longest time in human history, we believed that the ocean was so vast and the water volume so incredibly huge that any amount of pollution we introduced was going “away” by being so diluted that it would no longer be harmful to any living creature. 

From this practice stems the catchy phrase “the solution to pollution is dilution.”

As it turns out, this is delusion, as in: not true. Every part of the ocean today shows evidence of human pollution, whether in its chemical composition or visibly through the presence of plastics and other human-made debris.

This is true even for the deepest trenches and the most remote Islands. Not only do the natural sediments get washed into the ocean, but so do the breakdown products of human inventions that were designed to last for generations. 

Are we doomed? With ocean pollution, climate change, ocean acidification, extreme weather events and global pandemic disease, each and every one of us has felt some battering.

Some families were affected more than others, but no one’s life has been the same through the last year.

It turns out that there is one thing that people are really good at: coming together in times of need. Doing what needs to be done, overcoming huge obstacles and persisting.

As we persist today through a heat wave or a cold summer with flooding conditions, we may not like what is coming or what is already here, but we can adapt to climate change and changing weather.

Should the heat come to Kodiak, we can always take a dip in the sea at White Sands Beach, where the most recent storms have created an amazing new sand bar.

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