Timothy Horner

Tim Horner is a Geology professor at CSU Sacramento, a member of the Technical Advisory Committee (TAC) for Yolo County, and is one of three experts who advise Yolo County on the Cache Creek Resources Management Plan.  He advises on water quality issues within Cache Creek and helps mediate the competing interests of the mining industry, agriculture, and restoration of the creek.

Can we start by telling me your name and occupation, and your interests or expertise?

My name is Tim Horner and I’m a professor at Cal State Sacramento in the geology department.  I teach sedimentology and stratigraphy.  I’m really a hydrogeologist; I work a lot with streams and rivers in Northern California.  I specialize in salmon and steelhead habitat. 

Can you describe where we are right now?

We’re on the Cache Creek Nature Preserve right now.  This riparian area that is restored used to be a gravel mine.  The old mining sites are here but have been carefully restored.  The banks are graded down, and they have worked to get native vegetation here too.  The Cache Creek Conservancy has done a great job in restor[ing] the sites and try[ing] to eradicate the non-natives. 

Why is the tech committee important to the Cache Creek Nature Preserve?

On the TAC, Yolo County has 3 specialists that help manage their areas of professional expertise .  I’m an advisor on anything stream like and water quality in particular.  It’s a complicated system:  there’s mining, agriculture, issues with flooding.  It came out of the 1990’s when people realized they weren’t going to be able to mine gravel right in the channel forever.  That was really big to have agriculture, mining industry and environmentalists all on the same page.  This agreement where we manage this area of Cache Creek with these competing interests is an unusual setup.

What would you include as being 3 key geological aspects of the creek and why?

We’ve got these competing interests, so there’s mining, agriculture, and flood control.  There are places where there is a mine literally 200 feet from an active channel, and a big berm in the middle that keeps the flows out of the mining area.  But mines are right near the creek.  Mining companies don’t want the creek in the mining areas.  Mining is one of the major geologic features here.  Mining is part of the local economy and drives a lot of what is happening here.  I think about flood control where there are places where the channel is narrow.  It’s like a local pipeline that can hold a certain amount of water before its going to overflow.  Agriculture is the third thing.  The farmers use the creek water diverted through the local irrigation district, the Yolo County Flood Control and Water Conservation District.  Creek water is fundamental to the local economy and is essential to agriculture.  Yolo County has strong agricultural roots.  We’re always concerned about how much gravel is in the river and how much gravel is moving around.  I can find where the stream is scored right down to the bedrock; when that happens, we know how much gravel we have.  We have places where you have big thick gravel bars and that’s where the mining interests came from.  The places where you can see the bedrock is significant.  It’s a problem when it gets transported to the settling basin.  We’re worried about capacities and flood control.  I’m trying to paint a picture of a giant, broad marsh land that would have filled the Central Valley.  They say now that there is less than 5% of it left—I’ve heard there’s only 2% of it left.

How would you describe the geology of this part of the Cache Creek?

One is the bed rock, [which] underlies the creek sediments.  The bedrock is old volcanic deposits about 4 million years old.  There would have been volcanic peaks nearby; you’d see blasts of debris in the air.  When this volcano erupted, the area was blanketed in 4 feet of ash at times; it wouldn’t have been a friendly place when the volcanoes were erupting.  It was all compacted and lithified and turned into the bedrock.  The bedrock that we see around here is mostly old volcanic deposits.  It forms thick, impermeable benches that local people would probably call “clay”.  But a lot of that is essentially the volcanic ash from those older eruptions.  As the Coast Range was lifted up, sediment started to erode from the mountains and transported into local drainages.  Cache Creek is one of many that drain the Coast Range.  All these little sediment particles travel downhill and end up in big alluvial fans that go out into the Central Valley.  We’re on a low angle fan and these gravel deposits from Cache Creek have built up layer after layer of sediment in this fan.  We’ve got the bedrock underneath—a couple million years old—and then we’ve got the younger fluvial, which means river deposits. 

How can we understand the history of this place by understanding its geology?

This would have been one giant marshland that would have filled the Central Valley.  When the Europeans got here, they started building big drainage canals, draining the marshes and turning it into farmland.  What we try to do is think about sustainable models, if we can’t restore it, make it absolutely better.  Yolo County has done a wonderful job with the urban service boundary and [with] keeping agriculture land safe from development.  We can learn a lot about riparian zones or buffer zones from the prehistoric times.  If we’d have broader flood plains and wider backset levees then we’d be in better shape.  I am really concerned about flooding on Cache Creek.  We do have these competing interests; the best river for flood control is a big deep ditch that transmits the water quickly, but that may not be best for habitat, for farmers, or for bank stability.   One of the things that I think is really important here is that Woodland is right downstream and we do have limited flood capacity.  I’m really concerned about what happens the next time we have a wet winter and a high flow on the creek.  You have different views on how the land should be used, how the water should be used, and ultimately how things should be managed.