Archive for August, 2010

San Juan Report

Monday, August 30th, 2010

Attendees at the AWRA Summer Specialty Conference, August 30 – September 1, 2010, are getting their hydrology up close and personal. I’m home at JAWRA World Editorial HQ in Reston, but AWRA 2010 President Ari Michelsen reports, as of 11:37 EDT this morning, “As I write this we’ve got a Tropical Storm going. Looking out the window with blowing winds, high surf and rising tide. Conference is proceeding well with occasional power outages (so far brief ones). Some speakers report difficulty in getting here.”

Although I took a pass on attending this one, there are a number of fine talks scheduled. I’ve emailed a few presenters asking them to consider preparing a paper in JAWRA. I hope the power stays on and everyone stays dry!

Urban Drainage Networks Matter

Tuesday, August 24th, 2010

October 2010 Article: Analyses of Urban Drainage Network Structure and its Impact on Hydrologic Response, by Katherine L. Meierdiercks, James A. Smith, Mary Lynn Baeck, Andrew J. Miller

Urban flood studies have linked the severity of flooding to the percent imperviousness or land use classifications of a watershed, but relatively little attention has been given to the impact of urban drainage networks — including storm pipes, surface channels, street gutters, and stormwater management ponds — on hydrologic response. The authors demonstrate that drainage networks, like natural river networks, exhibit characteristic structures and that these features play critical roles in determining urban hydrologic response.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]

Modeling an Extreme Flood in Texas

Monday, August 23rd, 2010

October 2010 ArticleHydrologic Modeling of an Extreme Flood in the Guadalupe River in Texas, by Hatim O. Sharif, Almoutaz A. Hassan, Sazzad Bin-Shafique, Hongjie Xie2, Jon Zeitler.

"Flash Flood Alley"

One of the most flash flood prone areas in the U.S. is a region of South-Central Texas, called Flash Flood Alley (see figure) by local residents and weather experts. This dubious honor is the result of both climatic and geomorphic factors. In November 2004, a moist air mass from the Gulf of Mexico combined with moist air from the Pacific Ocean resulted in the wettest November in Texas since 1895. This paper examines the meteorological conditions that led to this event and applies a two-dimensional, physically based, distributed-parameter hydrologic model to simulate the response of a portion of the basin.

The study results clearly demonstrate the ability of physically based, distributed-parameter simulations, driven by operational radar rainfall products, to adequately model the cumulative effect of two rainfall events and route inflows from three upstream watersheds without the need for significant calibration. Results of simulation by the distributed model demonstrate the advantage of using quality-controlled radar products, which typically better characterize the spatial and temporal distribution of rainfall than rain gauges.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]

Testing Stream Restoration

Friday, August 20th, 2010

October 2010 Article: Design of Experimental Streams for Simulating Headwater Stream Restoration, by Jung-Chen Huang, William J. Mitsch, Andrew D. Ward.

Map of research facility

Stream restoration is a billion dollar industry in the U.S. — and a very controversial topic. JAWRA has published a number of articles on this topic in the past several years, and almost all have generated spirited discussions and replies. One problem is the uniqueness of each restoration project: a park agency restoring a stream, for example, is not inclined to build several different versions just to test the theories. At the Olentangy River Wetland Research Park, Columbus, Ohio, however, researchers are doing exactly that.

This study designs three experimental channels – two-stage, self-design, and straightened channels – on a human-created swale for long-term evaluation of headwater stream evolution after restoration. The swale receives a continuous flow of pumped river water from upstream wetlands. These stream channels, after construction, will be monitored to evaluate physical, chemical, and biological responses to different channels over a decade-long experiment.

This article is the first of what likely will be a series of journal articles over the years describing the progress of the restoration project. It looks at the characteristics of the facility and how the experimental channels are hypothesized to evolve.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]

101-year floodplain

Monday, August 16th, 2010

A recent article in the Washington Post, “As Fairfax updates flood plain map, residents must buy new insurance,” had an interesting connection to our 2010 Boggess Award winner. (See my August 4th posting.) Lauren A. Patterson and Martin W. Doyle, in their paper, “Assessing Effectiveness of National Flood Policy Through Spatiotemporal Monitoring of Socioeconomic Exposure,” note a significant increase in flood exposure immediately outside the 100-year floodplain. This is exactly the type of boundary affected by the new maps.

The revised maps, drawing upon new technology and better or updated data, move some homes in or out of the designated floodplain. Some residents are upset they now have to purchase flood insurance, others relieved they no longer have to. The relief or complaining seems to reflect a lack of understanding, as if some designated line on a map is going to hold back a flood. Flooding risk typically is a continuum, so the 101-year floodplain is only marginally safer than the 100-year floodplain. If I need a careful survey to determine whether my house is in or out, I’m still buying flood insurance!

Protecting the 100-year floodplain had focused our societal efforts on locations most vulnerable to flooding. However, it may be giving us an unrealistic sense of security against larger floods.

August 2010 Cover

Thursday, August 12th, 2010

Recent storms here in the east made me think more about the August 2010 cover. I took this photo in the afternoon from our 4th floor window in the Hotel Berchelli. (We splurged; Florence was too pretty to scrimp on!). Of course, I am well aware of what even such a peaceful-looking river can do.

Photo of Ponte Vecchio over the Arno River

In the early morning of November 4, 1966 the Arno River rampaged through the center of Florence leaving 5,000 homeless and damaging much of the priceless books and artwork of this Renaissance city. Photos show trees and debris piled up to the first level of windows on the upstream side of the bridge (opposite shown here). It’s a wonder the bridge survived at all. The Uffizi Gallery, one of the world’s great collections, can be seen just upstream to the left of the bridge, also in harms way.

Truly heroic work was done to restore much of the damaged treasures. The disaster ultimately contributed to significant research in the science of restoration. Some flood control measures have been taken upstream, though I don’t know the details. Practical museum administrators, however, have their own ways of reducing the risks. We noticed in visiting the galleries, while offices and shops were downstairs, one had to climb up to the second or third floors — well above the river — to see any artwork of value.

Documenting Channelization Effects

Monday, August 9th, 2010

August 2010 articleThe Effect of Channelization on Floodplain Sediment Deposition and Subsidence Along the Pocomoke River, Maryland, by Daniel E. Kroes and Cliff R. Hupp.

Channelization’s got to be one of these things that sounded like a good idea at the time. No doubt it achieved some immediate benefits and there are places today where we probably can’t do without it. The environmental price of massive channelization, however, has been very high.

The nontidal Pocomoke River was intensively ditched and channelized by the mid-1900s, and this article documents the effects. The sediment storage function of this river has been dramatically altered by channelization. Channelization has limited contact between streamflow and the floodplain, resulting in little or no sediment retention in channelized reaches. Additionally, the drainage of floodplains by improved channels has resulted in the oxidation of stored organic sediments, resulting in subsidence. The nutrient by-product (nitrates, phosphates) of this subsidence could be a contributor to the eutrophication of downstream water bodies; in this case, the already stressed Chesapeake Bay. Wish we knew all this when somebody made the decision to channelize!

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]

2010 Boggess Award

Wednesday, August 4th, 2010

AWRA President Ari M. Michelsen has announced the winners of the 2010 Boggess Award: Lauren A. Patterson and Martin W. Doyle, of the University of North Carolina. Their paper, “Assessing Effectiveness of National Flood Policy Through Spatiotemporal Monitoring of Socioeconomic Exposure,” was published in the February 2009 issue of JAWRA. The award will be presented at the luncheon of the AWRA 2010 Annual Conference, this November in Philadelphia. Congratulations to both authors!

The authors found a significant increase in flood exposure immediately outside the 100-year floodplain throughout North Carolina. As a result of this unintended consequence of national flood policy, any flood even slightly higher than the 100-year flood will have a disproportionately large impact, since development is outside the legal boundary of national flood policy.

The William R. Boggess Award is given to the author or authors of the paper, published in the Journal of the American Water Resources Association during the preceding year, that best describes, delineates, or analyzes a major problem or aspect of water resources from either a theoretical, applied, or philosophical standpoint. Established in 1973, the Award honors William R. “Randy” Boggess, a member of AWRA, one of the first Directors, and a former President of the Association, who has also made significant contributions to AWRA as an Editor of JAWRA.