Flooding Impacts

By Dave Sligh


The James was overflowing its banks in a number of places yesterday and many tributaries were roaring in the last several days, with some localized flooding. I'm thankful that I didn't see or hear of any human injuries or death. However, there was lots of damage done to stream channels because of the high flows. It's natural that periodic floods rearrange stream banks and habitats - in fact it's an essential process in the life of the stream. Our activities on the land though cause changes that aren't within the natural range and aren't beneficial.

The first photograph below shows a portion of a stream that I've observed over the last year. While this small section of the stream bank was already eroded and cut down to form a vertical wall of dirt, the recent high waters ripped away all of the dirt in this large depression. I'm not too experienced at estimating amounts of dirt but would guess that at least several tons of soil was carried downstream from a length of stream reaching no more than 100 yards. If you recognize that similar erosion effects occurred in dozens of other places on this same stream and multiply this by the thousands of small streams throughout the James River watershed, you can see the enormity of this problem.

You can see in the second picture (below) the stream bank across from that in the first view. This slope was covered all the way to the top of the slope with large stones (generally known as rip rap) in an attempt to stabilize the portion nearest the adjacent road. Almost all of the stones were washed away during this storm, showing that our human attempts at channel protection are sadly inferior to natural vegetative buffers and land cover.

This small tributary to Ivy Creek, in Albemarle County, is less than one mile in length upstream of the point shown in these photographs and this portion of the stream drains an area of about 0.5 square miles. The land is primarly in pastures with scattered home sites and a relatively small percentage of impermeable surfaces. However, the stream-side vegetative buffers are completely missing or very narrow along at least half of the stream's length. That this small watershed with primarily agricultural land can produce such force and destruction illustrates the extreme importance of maintaining stream buffer plantings and re-establishing them.

Finally, you can click on the link below and see a short news segment from Channel 19 TV in Charlottesville where I was interviewed describing this type of damage from high flows.




http://www.newsplex.com/video?clipID=4490640&autoStart=true&contentID=82706652

Flow Patterns in the James

By Dave Sligh

I've been looking at stream flow records during the last week to understand effects of human management and storms on stream flows in the James River basin. The graphs below show recent flows in the Jackson River, the stream which joins with the Cowpasture River to form the James, in the mountains of Alleghany County.

Releases of water from Gathright Dam control flows in the Jackson River and in the James River for a considerable distance downstream under many conditions. However, we can see that the effects of this recent storm has overridden the influence of the Dam. The first graph below shows that stream flows were maintained at a stable, low level below Gathright Dam through controlled releases by the Corps of Engineers which operates that dam. In contrast, the flows rose very sharply in the Jackson River at the stream gage below Dunlap Creek at Covington.

Flows rose very quickly in the Jackson during a 9 hour period, with an increase of over 400%. Several factors likely contributed to this drastic increase in flow over such a short period. Consistent rains in recent weeks have contributed to saturated soils so that much of the rainfall runs off the land rather than soaking into the ground and the steep mountain slopes in this area can contribute to rapid rises. Finally, there are fairly large percentages of impermeable surfaces (streets, parking lots, buildings, etc.) in the Covington area. To assess the relative contributions of these factors, we can look at storm-related flows during other times of year when the soil is drier and more likely to hold a larger percentage of rainfall that lands on vegetated areas.

I and others plan to make a long-term study of the effects of Gathright dam releases on the James River system. Wherever human actions and structures affect a natural system, we must periodically consider whether these factors can or should be altered to provide for better water quality, for competing human uses, and for the overall natural balance of the stream ecosystem.

Big Challenges For the James and the Bay

By Dave Sligh

I attended a meeting yesterday with citizens and officials from the Rivanna River watershed who are trying to see if they/we can help determine the way that EPA's newest efforts to protect the Chesapeake Bay can and should be applied in the area. I hope this effort can be a model that other citizens in watersheds throughout the upper James basin might emulate, because it could help local folks be more committed to following-through on the implimentation of pollution control plans. These plans are designed to benefit the Bay and all of the downstream resources but can and must correct significant problems from sediment and nutrient pollution in waters throughout the headwaters and Piedment areas of the James watershed.

If you don't yet know about initiatives that EPA, the states, and groups like ours are involved with to finally move Bay restoration forward forcefully, you might be interested to read some of the background materials. One good place to start is the Virginia DEQ's site at: http://www.deq.state.va.us/tmdl/chesapeakebay.html/chesapeakebay.html. We'll working to keep you up-to-date on these issues in the coming year or two and will need your help to support strong, specific cleanup goals and vigourous enforcement. Please also check out our brand new "State of the James" report - our report card on the River and its tributaries (http://jamesriverassociation.org/the-james-river/state-of-the-james/).

Finally, I'll leave you with a view of the Rivanna River this past summer, to remind you of the kinds of impacts an over-supply of nutrients can have on local streams.
























The solid-looking masses you see in the Rivanna are not rocks but large clots of algae that made the stream unpleasant for human use and are a symptom of water quality problems.