We have seen some unusually warm weather in the past week or so and most of the snow and ice has melted during this period. This past week the temperature rose to around +10 degrees Celsius for a couple of days, and has been above zero degrees for about a week. In December we received a record amount of snow fall, and the snow pack must have been around three feet, or one meter. The large amount of snow melting in a short period of time has increased the flood risk in several areas, including the Rideau Valley.
The Rideau Valley Conservation Authority has been issuing regular flood warnings and have been monitoring the situation closely. They were mostly concerned about the ice breaking up in the river, which could create an ice dam. An ice dam combined with increased water flows could quickly cause flooding in some areas. Their update yesterday indicated that they feel that the risk of flooding is low now, and that we have probably already reach the peak flow levels along the river.
I was not familiar with how they managed levels of water in the river before this thaw, but it has been interesting to watch the levels of the river and dams during this period. Last fall they lowered the level of the river so that it was probably over a foot below its normal summer levels. I am guessing that they were pretty glad that they had a good starting point when the temperatures rose so quickly this past week. It also looks like they recently lowered the dams again, and the river level has only increased slightly, but the river is flowing much faster than normal. Because of all of this, there is now a tremendous volume of water flowing over the dams along the river. I have included a photo of the dam near Watson’s Mill in Manotick below, which shows the peak levels of the river.
Although the RVCA does a great job of managing the River, this week has given me a healthy respect for the power of Mother Nature too. Just visiting one of the the dams along the river, you realize that an incredible amount of water was flowing into the river over the past few days. The RVCA indicated that this was similar to a normal spring thaw, but you could easily see it being much larger if this had happened later in the season, or if there was more rain combined with the mild weather.
To give you an idea of how large and fast the temperature change was, here is a photo of the second day of the big thaw. A few days earlier the temperature was close to minus 30 degrees celsius, and on the day when this picture was taken, it was closer to plus 5 degrees Celsius. As you can see below the sharp increase in temperature created a large amount of fog for a couple of days, which is very unusual for January in Ottawa. Also note the Coyote footprints near the hole in the ice in the photo below.
