Herschel Henderly was interviewed by Katy Barber in Eugene, Oregon on 23 October 1999.
B: Yes. Well, tell me, for example, what it was like to work here during the 1996, during the flood period. What were your responsibilities then during that kind of unique time?
H: Well, let me do a little background. Up until about 1990-92 when the dams were switched over to remote control the staff down here would have had the primary responsibility of actually operating the dam. The River Forecast Center in Portland with NOAH works very closely with the Corps of Engineers reservoir regulation people to determine what kind of flows they need from each dam and how much water needs to be held back in times of flood emergencies and they're operating all the dams in the Willamette Valley as a system so they all help, not only prevent floods immediately downstream from each dam but in concert, they're working to prevent dams further downstream at Salem and Albany and Portland where they all have an effect.
So up until 1990-92 when they switched to remote control, the duties would have been and were to stay close to the phone, take orders from Lookout Point which was told by the reservoir regulation people we need so many cubic feet per second from Cottage Grove Dam at this time and at another time we need more or less. You know, they'd tell you maybe go to 700 cfs at 9:00 am, go to 1200 at 10:00 am, go to 1700 and so on so we would spend quite a bit of time running back and forth to the dams and doing the calculations to figure what kind of gauge settings we needed to get those kind of flows.
Since '92, and '96 being the example you asked about, our duties in large part are to, number one, answer questions from the public because the public, especially in this local area know who were are. They're fairly familiar with our projects so we're the first people they call when they have questions about what's happening really. Many of them don't exactly trust the radio and television. They want to know from the horse's mouth. They'll call us. So, for example, in '96 on the 18th, 19th of November when we were having the flood event we probably took 150 calls here or some more than that. I mean, there were two of us answering the phones and as soon as you put the phone down it would ring again within seconds in many cases. So we were trying to answer the public's questions, tell them exactly where things stood.
The second duty was to coordinate with the people at Lookout Point and in reservoir regulations to let them know where things stand or stood. They, of course, have the telemetry so they know how many cubic feet per second were coming in, how many were going out, where the lake level is and how fast it's rising or falling. What they don't know, for example, is when they're discharging high amounts, high flows downstream and going past the normal operating perimeters what's happening. For example, these dams are designed ostensibly to control a hundred year flood, the theory being that if you have basically a one-time, a single event, flood event, one big storm and if starts when you have basically all of your flood control capacity available that you have a storm, you'll have a lot of inflow, you'll be able to contain it, and control that hundred year flood. What happened then was that at Dorena we actually had two hundred-year flows that night of November 18th. I think the two hundred-year flow level is like 39,000 and some cubic feet per second and we went over 39,000 and we only had a few readings that night so I'm sure we passed the two hundred year flood mark.
On one hand, we had basically the theoretically best possible event. We started with full flood control capacity available and had one big storm. We didn't have weeks and weeks of rain and saturated soils and a lake half full to begin with. Also, the flood event happened very quickly. The inflows went up very rapidly, they spiked, it stopped raining, and they dropped off very rapidly so we were able to contain that. On the other hand, if we had stuck with the normal operating perimeters, we'd have run over the spillway and lost control to some extent and what I'm talking about is that historically 5,000 cubic feet per second discharge was a maximum discharge at Dorena. We had never exceeded that to my knowledge since the dam was built and that was assumed to be, believed to be about the bank-full capacity of the river downstream.
When it was obvious that we were getting these extremely high flows the lake was filling very rapidly and if we didn't do something we were probably going to go over the spillway and lose control before the inflow dropped off to the point that the lake would stop rising the decision was made, well, let's see if we can keep jacking up the discharge without causing additional flooding downstream. So then we started taking turns, a couple people here answering the phones, another one driving up and down the Row River and the Coast Fork between here and, oh, I guess almost as far as Eugene watching the river level as they kept increasing the discharge from Dorena. So instead of 5,000 cfs maximum going out we went up to 7,000, 40% more and by going up that extra 40% we were able to control the flow downstream. It was more than we wanted but we were able to control it and keep the reservoir from filling to the point that it went over the spillway at which time we would have had no control. Does this all make sense?
H: Oh, good.
B: Did you have to evacuate people during the flood?
H: What we did, we didn't evacuate per se but that night when we were going up, or that afternoon when we were going up very rapidly and it was obvious that if it kept raining we were going to lose control – fortunately it stopped raining and we never went over the spillway but for a number of hours things looked fairly grim so we talked to the sheriff's office and
TAPE STOPS – electricity went out at the Cottage Grove dam office We pick up again the next day, 23 October 1999, at Henderly's home in Eugene, Oregon
H: Okay, to continue we didn't evacuate per se. That afternoon we realized that if it kept raining we would have water going over the spillway and we would lose control of how much water was going downstream. It could be a moderate amount or it could be enough to cause flooding so we contacted the Lane County Sheriff's office and the Cottage Grove Fire Department. They both provided officers and transportation to go out there and we worked out way downstream from just below the dam all the way to the junction of Row River and the Coast Fork warning people that there was a reasonable potential for flooding that night and they needed to be prepared to evacuate if necessary. If I remember correctly, we didn't start that until fairly late in the evening but I can't remember exactly what time off hand.
B: Do people get, does anybody in the area get flooded out in that area anymore?
H: No, downstream from the dams there hasn't really been any flooding since the dams went in. Let me take that back. In '64 water went over the spillway at Dorena in pretty substantial quantities. I wasn't here then. I would assume there was enough that there may have been some flooding downstream. Otherwise, no. Of course, as I said before, we went up to about 7,000 cubic feet per second which is 40% over the 5,000 limit at Dorena but even at that there wasn't any flooding of homes. There were some small outbuildings, woodpiles and things like that but no home flooding.
B: What about the debris that accumulated behind the dam after a flood?
H: We get fairly substantial amounts but to put it in perspective, when I came here in 1980 we were getting in normal precipitation years with normal inflows and freshets during the winter we got a pretty substantial amount of debris every year and what we did then and what we did after '96 was to take two boats and a log boom tug behind them in a "u" around the edge of the lake and work the edge of the lake pushing the debris that accumulates on the edge of the shoreline out past the most shoreward boats which collected in the boom and when the boom is full we tie it together and tow it to a collection point at Baker Bay and we do that in typically late May, early June. We collect all the major floating debris around the lake. Our goal is anything that weighs more than a couple pounds because a boat going at high speed or a water-skier could be damaged or injured hitting something like that so we get everything we can and tow it over to Baker Bay, excuse me, Hermes Park which is Rat Creek and dip it out with a crane and leave that for people to cut fire wood off of during the summer and then the next spring we burn whatever is left over and start over again.
The interesting thing is that, as I said, I came here in '80 and they'd been doing that for years. We did it through the late '80s. Late '80s we had some years with some fairly low precipitation, not a lot of flow during the winter and for two or three years we didn't collect any debris at all. There wasn't enough to put that much effort into and since then, given the changes in logging – there's less logging and they're staying away from streambeds more and stuff like that, that in '96 we had a good amount of debris, as much as we've ever collected in any individual year in the '80s but we haven't collect debris since then. Well, we collected a little bit last year but the amount of debris is way down from what it used to be.