Update 1: Channel Dimensions Changed - Two Meter Deeper and Bottom Slope Milder (明渠改深及底坡缓了）- Landslide Dam Removal at Tangjiashan "Quake Lake"

The channel inlet would be made two meters deeper, and the channel outlet one meter deeper. Over almost the same channel length, the bottom slope would be much milder at about half of what originally planned. The changed channel dimensions are: Length = 320 m, top width = 50 m, bottom width = 8 m. Depth at upstream end = 10 m, that is, the dam was excavated from the original top surface elevation of 750 m down to 740 m. Depth at downstream end = 13 m, that is, the dam was excavated from the original top surface elevation of 752 m down to 739 m. The channel is expected to be completed by noon (New York time) or midnight (Beijing time) today.

At 14:10 Beijing time, the lake water level was 734 m, still 6 m below the channel bottom. The water level rising speed was 1.5 m per day. The lake level is expected to rise up to the channel bottom in three or four days and the water would start to discharge downstream through the channel.

Change to the deeper channel was attributed to a desire for an earlier water release (because of the decreased channel bottom elevation). They were able to make this change because the construction was several days ahead of schedule. The original plan to blow open an entrance to the drainage channel using explosives was also scraped since it was no longer necessary. The change to a milder bottom slope was not explained.

Due to complex and likely unknown soil properties of the massive landslide dam, there would still be a possibility of catotrophic collapse even with a proper design and construction of the drainage channel.

All the 190,000 people expected to be affected by the 1/3 dam collapse scenario have been evacuated.

I would define success as the downstream water level rises to or below that projected for the 1/3 dam collapse scenario. I am of course hoping for a smaller water level rise downstream (thus less damages) if the water release and dam removal would indeed occur slowly.

Yesterday, I sent my best wishes and my thoughts (or reminder) on proper design and construction of the drainage channel to the China Ministry of Water Resources. This is possibly the best thing that I could do for my motherland within the distance and time constraints.

“修好(改变)后的导流明渠全长320多米，顶宽50米，底宽8米。上游深度为10米。就是从原来的750高程降低到现在的740高程。下游深度为13米，也就是从原来的752高程降低到现在的739高程。导流明渠修好后将不再实施爆破导流，而是自然溢流。"

"目前，唐家山堰塞湖的水位是734米，距离最低过流面740还有6米，目前水位增长速度是每天1.5米左右。以这种速度计算的话，三、四天后唐家山堰塞湖将开始导流。"

"按唐家山堰塞湖三分之一溃坝方案需撤离的绵阳十九万民众今天上午八点已全部转移到安全地带。”

我认为如果排水除坝过程中下游水位不超过三分之一溃坝方案线, 就是成功。当然， 我希望湖水会真的慢慢下降，下游水位会上升更底而损失更小。

我已于昨天把我最良好的祝愿和对导流明渠最优设计与建造的想法(或提醒)发送给了中国水利部。由于距离及时间的限制，这也许是我能为我的祖国做的最好的事。

Info source: CCTV.com

The Most Daring Landslide Dam Removal in Human History: Proper Design and Construction of Drainage Channel is Key to Success (唐家山堰塞湖-泄洪槽设计和建造是成功关键)

It just came to my full realization that the Chinese authorities are actually trying to release the water and remove the landslide debris/dam simultaneously at the Tangjiashan "quake lake." Apparently, keeping the dam in place was not an option. The dam removal and water release operation will start within several days!

A drainage/sluice channel is being dug through top of the dam, and is almost completed (see photo to the left). Once the water starts to flow in the channel, water current will scour the channel bottom and the channel sides. The channel will become wider and deeper while water level in the "quake lake" will be lower and lower. The channel bottom and sides will scour because of steep slope of the channel being dug.

If it works perfectly, a good mixture of debris/soil and water will be flowing gradually downstream, water in the lake will be draining down slowly, and the dam itself will disappear steadily. In this scenario, the flooding downstream will be minimal, although some debris/soil will deposit along the way.

However, if scour of the channel is not gradual and initial release of the water triggers a catastrophic collapse of the dam, entire volume of the lake water will rush downstream rapidly, leading to devastating downstream flooding and destruction.

Therefore, this daring engineering has to be designed and executed extremely carefully. A detailed hydrodynamic and sediment transport analysis (including computer modeling and physical modeling which Chinese engineers are fully capable of conducting) would help properly design and construct the channel. A reinforcement at downstream end of the channel and/or diversion of the released water far away from toe of the dam may also be necessary.

The best wishes to the Chinese endeavors!!!

The channel dimensions are: Channel length = 300 m, bottom width = 13 m, top width = 50 m, inlet bottom elevation = 742 m, outlet elevation = 740 m (i.e., an elevation drop of 2 m over the length of 300 m, a steep slope that will definitely result in soil scour once the water flow starts), upstream depth = 8 m, downstream = 12 m. Total volume of the debris/dam = 20,370,000 cubic meters. At 8:00 a.m. of May 29, 2008 (Beijing time), lake water level = 730.13 m (rising), water depth = 62.58 m, lake water volume = 161,000,000 cubic meters.

Three downstream evacuation plans were planned: 1/3 of the dam opened up instantly, 1/2 of the dam opened up instantly, and the entire dam opened up instantly (the catastrophic collapse). Nearly 200,000 downstream people are being evacuated based on the scenario of 1/3 dam collapse. More than one million people are on alert, and they would have to be evacuated if the total collapse, in addition to inconceivable property and natural environment damages. A lot is at stake, and it is obviously highly desirable to have a well engineered slow dam removal and water release.

The Chinese Short Version:

从媒体报道得知，唐家山堰塞湖的泄洪槽(导流槽)已基本上修完。 湖水面在近日就会上升至槽（渠）底开始排水。

因为新修的渠比较陡 （300 米距离内底部高程降2米），放水一开始，渠道就会冲刷。我想这是中国工程师预期的效果，既边排放湖水，边冲走堰塞土堆/坝。

我相信中国的水利专家已经为决策高层设计了最佳的渠道高程，断面，和坡度。修造最佳的渠道可以达到缓慢放水，平稳冲涮（除坝）的目的。最佳设计可以先通过水动力学与泥沙传输原理简单计算得出，然后最好再用复杂的数学模型及/或大型物理模型验证。万一这一步还没做，需马上请国内专家算， 以作渠道调整。我在美国也可以帮
算，但需要土质资料。

我还想提醒中国工程师的是要用当地石块加固坝的下游底面和河床，以避免坝趾掏空而溃堤。

祝唐家山堰塞湖排水成功！

Photo credit and info source: CCTV.com

The Highest Annual Rainfall in the World: Wailua River on Kauai Island, Hawaii

A photo that I took of the Wailua River on the island of Kaua'i, looking downstream toward the Pacific Ocean. The headwater area of this river receives the highest annual rainfall in the world, at 460 inches (11,700 mm).

I was in Hawaii last week attending the ASCE/EWRI Environmental and Water Resources Congress. I presented a paper and moderated a technical session on certification guidelines for stormwater manufactured treatment devices, and later presided over a committee meeting on the same topic.

While enjoying the nice weather and beautiful scenery in Hawai'i, I was saddened by the devastating news of earthquake in China.

My ablum contains additional photos of the Hauai Island.

Final Report Published: Stormwater Management Rule Implementation Process for Highway Projects

"Stormwater Management Rule Implementation Process," a final report prepared by our project team, was made available for public downloading by the New Jersey Department of Transportation (NJDOT) (Report Number: FHWA-NJ-2007-23).

The New Jersey Department of Environmental Protection (NJDEP)’s Stormwater Management Rules (N.J.A.C. 7:8), adopted on February 2, 2004, has created more stringent storm water management standards for land developments in the state, including roadway and other transportation projects. These Rules include requirements for groundwater recharge and both stormwater quality and quantity control. A Stormwater Best Management Practices (BMP) Manual was developed by the NJDEP to assist regulated agencies such as the NJDOT with Rule compliance. However, the BMP Manual lacks sufficient guidance to properly lead engineers to identify applicable regulations and select appropriate storm water management measures for transportation projects.

As a result, NJDOT planners, designers, and maintenance personnel need a simplified process to navigate the Stormwater Management Rules and facilitate the selection of appropriate stormwater management measures. This report documents the development of an electronic decision-making program in Microsoft Excel that provides such a process. This program also assists NJDOT personnel in determining during early project stages whether all of the requirements of the Rules can be met for a specific project or whether hardship waivers will be necessary.

Our research project team consisted of Rutgers University, Gannett Fleming, and Storm Water Management Consulting, LLC.

(My presentation contains additional info on the project.)

Rain Chains

On December 10, 2007, I attended a meeting of the ASCE/EWRI Stormwater M-BMP Maintenance Subcommittee on North Carolina State University campus in Raleigh.

After the meeting, Professor Bill Hunt, the Subcommittee Chair, took us for a field trip to several rainfall/stormwater management sites on campus. One of the photos that I took (shown to the left) was on "rain chains."

"Rain chains do exactly what downspouts do, but they do it in a way that brings visual pleasure and delight. Rain swirls and flows down, creating a mesmerizing sense of motion and tranquility right outside your window." (www.HarvestH2O.com)

Baltimore Inner Harbor

My family and I visited Baltimore's Inner Harbor last Friday and Saturday, one of the America's oldest seaports - and one of the world's newest travel destinations. I was very impressed by the transformation of an abandoned area of rotting warehouses and piers to a major cultural and economic area of the city. I think this is an excellent example of waterfront re-development.

However, water quality could be improved. Visibility of the water was almost zero, and floatables were occasionally visible from the water taxi that we took. In addition to control of municipal and industrial discharges, stormwater runoff from the street needs to be intercepted and treated, as it could carry a large amount of trash, debris, oil, grease, sediment, and other pollutants to the harbor. Being an "inner" harbor that has a very limited pollutant flushing capability, control of the pollutant sources is critical.

Tour of the National Aquarium was fantastic! I believe everybody would appreciate watershed and salt marsh much more after seeing the exhibit "Maryland: Mountains to the Sea.

My album contains additional photos of the Baltimore's Inner Harbor.

Dam Operations to Help with Recovery and Reconstruction Efforts at Collapsed I-35W Bridge Site

It was reported that the recovery (sadly) efforts were hindered by the rapid and turbid river current at the collapsed I-35W Bridge site. I believe the rapid current was due to water falls upstream, and the turbid water was due to its high soil and organic contents that was made worse by debris from the collapsed bridge.

The Google map/image shows the I-35W Bridge, and the Upper and Lower St. Anthony Falls. You can see the rapid currents at downstream sides of both Falls. The I-35W Bridge is in rapid tail water of the Lower St. Anthony Falls.

To help the recovery efforts, water level was lowered in the Mississippi River at the bridge site, by opening up more the downstream Ford Dam (a part of the Lock and Dam No. 1 System). But this made the current at the bridge site even faster, thus tougher to anchor and stirring up even more debris. It was a tricky engineering that helped with the recovery efforts.

Maybe they could additionally change operations at the lock and dam systems associated with the St. Anthony Falls upstream, and lower the gates at the Coon Rapids Dam further upstream to hold more water.

Well-coordinated opeartions of downstream and upstream dams would also likely help a rapid and smooth reconstruction of the bridge.

What a horrible event! May the recovery and re-construction efforts go well!

PS: I lived in a rooming house close to the bridge while a graduate student at the University of Minnesota. I still remember the sound of I-35W traffic as well as the view of St. Anthony Falls!