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geomorphology

Braided river meets mountain gorge: The Snake River escapes Jackson Hole

Though I don’t think anything can top Kyle’s pathologically misdirected RYNHO, I recently had cause to contemplate a river that everyone has heard of – the Snake River of the northwestern United States. Now, the Snake River has a famous gorge, a famous lava plain, and it’s had a famously big flood or two, but the upper reaches of the Snake are pretty scenic too. The Snake originates in Yellowstone National Park and flows through Grand Teton National Park and the Jackson Hole valley. Throughout the broad, flat valley, the Snake is beautifully braided (with some gorgeous terraces too).Then it runs into some mountains – the Wyoming Range – and it runs out of room to braid, becoming constricted into a narrow mountain gorge. Interestingly, after heading south from Yellowstone and through Jackson Hole, the river turns west through the mountains and then quite abruptly turns north towards Idaho’s Snake River Plain.

I’d love to know how and why the river started along this path and how intensely the river’s course is geologically controlled. I think the gorge is south of the Teton block, and it’s possible that it’s in an narrow zone that hasn’t seen as much uplift as other mountain blocks in the Basin and Range, but I’m just speculating here. If anyone has any good ideas or citations, please drop them in the comments.

The images below are from a mix of Flash Earth (permalink here) and Google Earth. The first is a large scale view of the braided-gorge transition, while the second and third are close-ups of typical braided and gorge reaches, respectively.

Posted via web from Pathological Geomorphology

New publication: Coevolution of hydrology and topography on a basalt landscape in the Oregon Cascade Range, USA

ResearchBlogging.org

How does a landscape go from looking like this…

<2000 year old landscape on basaltic lava with no surface drainage

~1500 year old basaltic lava landscape with no surface drainage

to looking like this?

2 Million year old landscape on basaltic lava

2 Million year old landscape on basaltic lava. Note steep slopes and incised valleys

Find out in my new paper in Earth Surface Processes and Landforms.

Hint: Using a chronosequence of watersheds in the Oregon Cascades, we argue that the rates and processes of landscape evolution are driven by whether the water sinks into the lava flows and moves slowly toward springs with steady hydrographs or whether the water moves quickly through the shallow subsurface and creates streams with flashy hydrographs. Further, we suggest that this water routing is controlled by an elusive landscape-scale permeability which decreases over time as processes like chemical weathering create soil and clog up pores in the rock. And as a bonus, because of the high initial permeability of basaltic landscapes, the formation of stream networks and the dissection of the landscape appears to take far longer than in places with less permeable lithologies.

Jefferson, A., Grant, G., Lewis, S., & Lancaster, S. (2010). Coevolution of hydrology and topography on a basalt landscape in the Oregon Cascade Range, USA Earth Surface Processes and Landforms, 35 (7), 803-816 DOI: 10.1002/esp.1976

When it rains a lot and the mountains fall down

Cross-posted at Highly Allochthonous

2006 debris flow deposit in the Eliot Glacier drainage, north flank of Mount Hood (Photo by Anne Jefferson)

The geo-image bonanza of this month’s Accretionary Wedge gives me a good reason to make good on a promise I made a few months ago. I promised to write about what can happen on the flanks of Pacific Northwest volcanoes when a warm, heavy rainfall hits glacial ice at the end of a long melt season. The image above shows the result…warm heavy rainfall + glaciers + steep mountain flanks + exposed unconsolidated sediments are a recipe for debris flows in the Cascades. Let me tell you the story of this one.

It was the first week of November 2006, and a “pineapple express” (warm, wet air from the tropic Pacific) had moved into the Pacific Northwest. This warm front increased temperatures and brought rain to the Cascades…a lot of rain. In the vicinity of Mt. Hood, there was more than 34 cm in 6 days, and that’s at elevations where we have rain gages. Higher on the mountain, there may even have been more rain…and because it was warm, it was *all* rain. Normally, at this time of year, the high mountain areas would only get snow.

While it was raining, my collaborators and I were sitting in our cozy, dry offices in Corvallis, planning a really cool project to look at the impact of climate change on glacial meltwater contributions to the agriculturally-important Hood River valley. Outside, nature was opting to make our on-next field season a bit more tricky. We planned to install stream gages at the toe of the Eliot and Coe glaciers on the north flank of Mt. Hood, as well as farther downstream where water is diverted for irrigation. But instead of nice, neat, stable stream channels, when we went out to scout field sites the following spring, we were greeted by scenes like the one above.

Because sometime on 6 or 7 November, the mountain flank below Eliot Glacier gave way…triggering a massive debris flow that roared down Eliot Creek, bulking up with sediment along the way and completely obliterating any signs of the pre-existing stream channel. By the time the flow reached the area where the irrigation diversion occur, it had traveled 7 km in length and 1000 m in elevation, and it had finally reached the point where the valley opens up and the slope decreases. So the sediment began to drop out. And debris flows can carry some big stuff (like the picture below) and like the bridge that was washed out, carried downstream 100 m and turned sideways.

2006 Eliot Glacier debris flow deposit (photo by Anne Jefferson)

2006 Eliot Glacier debris flow deposit (photo by Anne Jefferson)

In this area, the deposit is at least 300 m wide and at least a few meters deep.

Eliot Creek, April 2007 (photo by Anne Jefferson)

Eliot Creek, April 2007 (photo by Anne Jefferson)

With all the big debris settling out, farther downstream the river was content to just flood…

[youtube=http://www.youtube.com/watch?v=J4eduMJU710]
Youtube video from dankleinsmith of the Hood River flooding at the Farmers Irrigation Headgates

and flood…

West Fork Hood River flood, November 2006 from http://elskablog.wordpress.com/2006/11

West Fork Hood River flood, November 2006 from http://elskablog.wordpress.com/2006/11/. For the same view during normal flows, take a look at my picture from April 2007: http://scienceblogs.com/highlyallochthonous/upload/2009/10/IMG_1108.JPG.

and create a new delta where Hood River enters the Columbia.

Hood River delta created in November 2006 (photo found at http://www.city-data.com/picfilesc/picc30876.php)

Hood River delta created in November 2006 (photo found at http://www.city-data.com/picfilesc/picc30876.php

And it wasn’t just Mt. Hood’s Eliot Glacier drainage that took a beating in this event. Of the 11 drainages on Mt. Hood, seven experienced debris flows, including a rather spectacular one at White River that closed the main access to a popular ski resort. And every major volcano from Mt. Jefferson to Mt. Rainier experienced debris flows, with repercussions ranging from downstream turbidity affecting the water supply for the city of Salem to the destruction of popular trails, roads, and campgrounds in Mt. Rainier National Park (pdf, but very cool photos).

In the end, our project on climate change and glacial meltwater was funded, we managed to collect some neat data in the Eliot and Coe watersheds in the summer of 2007, and the resulting paper is wending its way through review. The November 2006 debris flows triggered at least two MS thesis projects and some serious public attention to debris flow hazards in the Pacific Northwest. They also gave me some really cool pictures.

FYI: NCED Summer Institute on Earth-surface Dynamics

I basically recommend anything this NCED group puts together. The short courses on Mountain Rivers and Sand-bed Rivers that I took as late-stage PhD student were absolutely fantastic.

HOW DOES VEGETATION INFLUENCE LARGE-SCALE TOPOGRAPHIC FORM?
—————————————————————————————————————————–
In order to adequately describe the interactions among the physical, biological, geochemical, and anthropogenic processes that shape the Earth’s surface, we need to take a holistic, cross-disciplinary approach. Thus, the National Center for Earth-surface Dynamics (NCED) founded the Summer Institute on Earth-surface Dynamics (SIESD) as a forum to expose early-career scientists to laboratory experiments, fieldwork, and lectures on predictive Earth-surface science.

In 2010, the Summer Institute will focus on the science of rivers and vegetation. Participants will gain experience in: the basic physics of water-sediment-vegetation interaction; modeling the co-evolution of landscapes and their ecosystems; quantitative analysis of complex landscapes; LiDAR analysis of river topography and vegetation; and specifics of braided, meandering, and deltaic systems interacting with vegetation. In addition, students will gain hands-on experience with a suite of analytical tools including GeoNet (an automatic feature extraction tool for high resolution topography) and InVEST (a modeling environment to support environmental decision-making).The Institute will also expose students to broader-impacts research via the Science Museum of Minnesota and other NCED educational and diversity activities.

Eligibility: The Summer Institute is directed to graduate students in the final years of their PhD program, postdocs, or early-career scientists (three years from PhD). Applications from women, minorities, and individuals with disabilities are strongly encouraged.

Cost: NCED will make arrangements to cover local expenses related to participation in the Institute (enrollment, accommodations, breakfast, and lunch). However, students should remember they are responsible for the cost of transportation to/from Minnesota and all incidental expenses. Limited resources are available to cover travel expenses upon request.

Application Procedure: An online application is available at: http://www.nced.umn.edu/content/2010-summer-institute-earth-surface-dynamics-siesd-application.

Lecturers (subject to change): Chris Paola, Gary Parker, Brad Murray, Gordon Grant, Steve Polasky, and Efi Foufoula-Georgiou. Additional lecturers will be announced on the course website.

Deadline: The application and all supporting materials must be received by June 25, 2010.

For more information, please visit http://www.nced.umn.edu/content/summer-institute-earth-surface-dynamics.

Delta upon Delta

For some reason the last few days have seen me browsing the semi-frozen areas of the Earth and in my search for the perfect thermokarst landscape, I’ve run across some really nice deltas. I don’t know anything about the one below other than its location in far northwestern Saskatchewan, but it looks to me like this river had built a beautiful fan delta only to see the lake shoreline dramatically change (perhaps as a result of isostatic rebound?) triggering the building of not one, but two, new fan deltas like Mickey Mouse ears on the margins of the old one.

The image below is from Google Earth. Here’s the Flash Earth permanent link: http://www.flashearth.com/?lat=59.114818&lon=-109.354195&z=11.9&r…

Posted via web from Pathological Geomorphology

More tributes to Reds Wolman from all those who miss him

About two months ago, I noted with great sadness the passing of a legendary figure in fluvial geomorphology, M. Gordon “Reds” Wolman, long-time professor at The Johns Hopkins University and inspiration to hundreds, if not thousands, of geomorphologists, hydrologists, and environmental scientists around the world.

In the past two months, Wolman’s students and colleagues have done an outstanding job of paying tribute to our hero. On April 11th, generations of Wolman’s students gathered on the Hopkins campus for a memorial service, which included a eulogy from a childhood friend and reflections from Hopkins geomorphology colleague Peter Wilcock. The day before the memorial, many of the attendees conducted their own Reds’ style field trip to some of his favorite locations in Baltimore County and waved their arms and debated some of the same questions Reds had spent decades pondering. (Sadly, I could not attend the celebration, because I was leading my hydrogeology class on a field trip to Congaree National Park, but somehow I feel like Reds would understand.)

Among the lasting tributes to Wolman are a couple of JHU web pages, two wonderful videos (below), and perhaps my favorite memorial ever:

A permanent memorial tribute will be installed outside the classrooms in Ames Hall where Reds Wolman taught for more than a half century. Stones provided by students, colleagues and friends from around the world will be constructed into a path in a shape that mirrors a meandering river.

For those of you still wondering what all the fuss was about (and still reading this post), please take a few more minutes and listen to the preface of one of Wolman’s seminal works and some reflections from Wolman’s colleagues and students (including, if you listen carefully, me) and from Wolman himself.

[youtube=http://www.youtube.com/watch?v=-vCDJ8T5usY&hl=en_US&fs=1&]

[youtube=http://www.youtube.com/watch?v=iB2e0Ei04pg&hl=en_US&fs=1&]

Reds is deeply missed by all who knew him, but these wonderful tributes give us a small way to hang on to the man who influenced, encouraged, and inspired us.

Deltas into Rivers: Chippewa River into the Mississippi River, Wisconsin

The Chippewa River drains the glaciated terrains of north-central Wisconsin including major outwash plains from the margins of the Laurentide Ice Sheet.  The sand carried by the Chippewa is a major sediment source for the Upper Mississippi River for tens of miles downstream.  The Chippewa forms a beautiful delta into the Mississppi River, as seen below, creating the only natural lake on the Mississippi, in the form of Lake Pepin (birthplace of water-skiing, by the way).  I like this delta because we don’t often think of riverine deltas forming in the rivers, and their propogating upstream and downstream effects. Plus, it makes a pretty contrast to the dissected blufflands of the Driftless area.

Flash earth link: http://www.flashearth.com/?lat=44.418021&lon=-92.140805&z=11.6&r=0&src=msa If you zoom in on Flash Earth you can get some nice imagery of the sand bars and fluvial islands of the Chippewa as you move upstream, plus some nice long anastomosing reaches.

Posted via email from Pathological Geomorphology

The pathologically curvy Rio Grande Delta

I spent a summer in college staring at maps and aerial photographs of the Rio Grande delta in Texas and Mexico. Maybe now I can get some use out of it.  I was working with J.D.  Stanley at the Smithsonian’s NMNH and he pointed me to the apparently high sinuosity of deltaic channels on the Texas side of the Rio Grande delta.

According to my notes, the modern Rio Grande has a sinuosity of 2.075 in its delta, while Holocene channels have a sinuosity of 1.83, younger Pleistocene channels have a sinuosity of 1.81 and remnants of older Pleistocene channels have about 1.32. So our data suggests that the channels of the Rio Grande delta have gotten curvier over time. I also did a literature review of channel sinuosity in other deltas and found that the Rio Grande was indeed anomalously sinuous compared to many of the world’s major deltas.  In my review, only the Niger and Klangat Langat deltas were curvier. Unfortunately, we never came up with a good mechanism to explain why the Rio Grande was so curvaceous.

Indeed, if you look at the flash earth images (http://www.flashearth.com/?lat=26.07433&lon=-97.526349&z=10.4&r=0&src=msa)  below, you can see what caught our eye. One of the images is the majority of the delta (look for the anthropogenically straightened main outlet channel), one zooms in on the modern river mouth and area just to the north, one shows a portion of the southern, Mexico portion of the delta, and one shows the northern portion of the delta, which if I recall correctly has some of the oldest exposed deltaic deposits along with some eolian features (which can been seen in the image).

Posted via email from Pathological Geomorphology

Bombetoka Bay, Madagascar

Hunting for a Where on Google Earth location a while ago I ran across this wonderful tidally-influenced delta on the northwest coast of Madagascar. It is the mouth of the Betsiboka River and just north of the river mouth is the second largest port in Madagascar.

What struck me about the delta was not just the nice tug-of-war between riverine and tidal processes in shaping the islands, but the dramatic red color of the water in the Google Earth image (and others as well). This red color is symptomatic of the massive erosion resulting from rampant deforestation of the island.

The four photos are from Flash Earth, Google Earth, and the Gateway to Astronaut Photography, NASA Earth Observatory (ASTER satellite)

Flash earth permanent link: http://www.flashearth.com/?lat=-15.883853&lon=46.436067&z=10.8&r=0&src=msa

Astronaut Photograph: http://eol.jsc.nasa.gov/scripts/sseop/photo.pl?mission=ISS005&roll=E&frame=9418

Earth Observatory ASTER image: http://earthobservatory.nasa.gov/IOTD/view.php?id=5245

Posted via email from Pathological Geomorphology

Is Anne a hydrologist? geomorphologist? hydrophillic geologist? or whathaveyou?

Cross-posted at Highly Allochthonous

The theme for the next edition of the geoblogosphere’s Accretionary Wedge carnival is along the lines of “what are you doing now?” Recently as I was whining to my Highly Allochthonous co-blogger about how busy my teaching was keeping me, and how I wouldn’t have time to write anything for the Wedge, Chris suggested that I exhume some navel-gazing writing I’d done a while ago and simply post that. And in slightly modified form, now I have.

So, what do I do? The major theme of my research is analyzing how geologic, topographic, and land use variability controls hydrologic response, climate sensitivity, and geomorphic evolution of watersheds, by partitioning water between surface and ground water. The goal of my research is to improve reach- to landscape-scale prediction of hydrologic and geomorphic response to human activities and climate change. My work includes contributions from field studies, stable isotope analyses, time series analyses, geographic information systems, and hydrological modeling. My process-based research projects allow me to investigate complex interactions between hydrology, geomorphology, geology, and biology that occur on real landscapes, to test conceptual models about catchment functioning, and to show whether predictive models are getting the right answers for the right reasons. My current and past research has allowed me to investigate landscapes as diverse as the Cascades Range volcanic arc, the Appalachian Mountains and Piedmont of the southeastern United States, the Canadian Arctic Archipelago, and the Upper Mississippi River watershed.

My on-going and developing research program focuses on three areas:

  1. Watershed influences on hydrologic response to climate variability and change;
  2. Controls on and effects of partitioning flowpaths between surface water and groundwater; and
  3. Influence of hydrologic regimes on landscape evolution and fluvial geomorphology

If you really want the long version of my research interests, venture onward. But don’t say I didn’t warn you.

Watershed influences on hydrologic response to climate variability and change

On-going climate change is predicted to have dramatic effects on the spatial distribution and timing of water resource availability. I use historical datasets, hydrologic modeling, and GIS analysis to examine how watershed characteristics can mediate hydrologic sensitivity to climate variability and change. Currently, I focus on climate sensitivity in watersheds with seasonal and transient snow and on down-scaling hydrologic impacts of climate change to smaller watersheds.

Watersheds with seasonal and transient snow: A long-held mantra is that watersheds with extensive groundwater are buffered from climate change effects, but in a pair of papers set in the Oregon Cascades, my collaborators and I showed the opposite to be true. Minimum streamflows in watersheds with abundant groundwater are more sensitive to loss of winter snowpack than in watersheds with little groundwater (Jefferson et al., 2008, Tague et al., 2008). Glaciers are another water reservoir often thought to buffer climate change impacts, and in a paper in review, we show that projected glacier loss from Mt. Hood will have significant impacts on water resources in the agricultural region downstream.

I have also been examining hydroclimate trends relative to hypsometry (elevation distribution) of watersheds in the maritime Pacific Northwest. Almost all work investigating hydrologic effects of climate change in the mountainous western United States focuses on areas with seasonal snowpacks, but in the maritime Northwest, most watersheds receive a mixture of winter rain and snow. My research investigates how much high-elevation watershed area is necessary for historical climate warming to be statistically detectable in streamflow records. Preliminary results were presented at the American Geophysical Union meeting in 2008, and I’m working on a paper with more complete results. Extending this work into the modeling domain, I am currently advising a graduate student using SnowModel to investigate the sensitivity of snowmelt production to projected warming in the Oregon Cascades, Colorado’s Fraser Experimental Forest, and Alaska’s North Slope, in collaboration with Glen Liston (Colorado State University).

Down-scaling climate impacts to watersheds and headwater streams: Most studies of hydrologic impacts of climate change have focused on regional scale projections or large watersheds. Relatively little work has been done to understand how hydrologic and geomorphic impacts will be felt in mesoscale catchments or headwater stream systems, yet most of the channel network (and aquatic habitat) exists in these small streams. In August 2009, I submitted a proposal to a Department of Energy early career program to investigate the effect of climate change on hydrology of the eastern seaboard of the US. This work proposed to contrast North Carolina’s South Fork Catawba River and New Hampshire’s Pemigewassett River and their headwater tributaries through a combination of modeling and field observations of the sensitivity of headwater stream networks to hydroclimatic variability. While the project was not funded, I am using the reviews to strengthen the proposal, and I plan to submit a revised proposal to NSF’s CAREER program in July. I have a graduate student already working on calibrating the RHESSys hydroecological model for the South Fork of the Catawba River.

Controls on flowpath partitioning between surface water and groundwater and the effects on stream hydrology, geomorphology and water quality

Many watershed models used in research and management applications make simplifying assumptions that partition water based on soil type and homogeneous porous bedrock. These assumptions are not reflective of reality in many parts of the world, including the fractured rocks of North Carolina’s Piedmont and Blue Ridge provinces. I am interested in understanding how water is partitioned between groundwater and surface water in heterogeneous environments, and what effect this partitioning has on stream hydrology, geomorphology, and water quality. My interest in the controls on flowpath partitioning began during my work in the Oregon Cascades Range, where I showed that lava flow geometry controlled groundwater flowpaths and the expression of springs (Jefferson et al., 2006). Currently, I am using fractured rock environments and urbanizing areas as places to explore the effects of heterogeneous permeability.

Fractured rock: The Piedmont and Blue Ridge provinces of the eastern United States are underlain by crystalline rocks, where groundwater is largely limited to discrete fractures. Groundwater-surface water interactions on fractured bedrock are largely unexplored, particularly at the scale of small headwater streams. I am interested in how groundwater upwelling from bedrock fractures and hyporheic flow influence the hydrology and water quality of headwater streams. A small grant facilitated data collection in three headwater streams which is forming the thesis for one of my graduate students, has precipitated a collaborative project with hydrogeologists from the North Carolina Division of Water Quality, and will serve as preliminary data for a proposal to NSF Hydrologic Sciences in June 2010.

Urban watersheds: Urbanization alters the partitioning of flowpaths between surface water and groundwater, by creating impervious surfaces that block recharge and installing leaky water and sewer lines that import water from beyond watershed boundaries. Also, the nature of the drainage network is transformed by the addition of stormwater sewers and detention basins. In September 2009, my collaborators and I submitted a proposal to NSF Environmental Engineering to look at how stormwater best management practices (BMPs) mitigate the effects of urbanization on headwater stream ecosystem services. While we weren’t funded, we were strongly encouraged to resubmit and did so in March 2010. We are also submitting a proposal to the National Center for Earth Surface Dynamics (NCED) visitor program to use the Outdoor Stream Lab at the University of Minnesota to investigate the interplay between stormwater releases and in-stream structures.

Influence of hydrologic regimes on landscape evolution and fluvial geomorphology

The movement of water on and through the landscape results in weathering, erosion, transport, and deposition of sediment. In turn, that sediment constrains the future routing of water. I am interested in how the hydrologic regime of a watershed affects the evolution of topography and fluvial geomorphology. My work in this area has examined million-year scales of landscape evolution in high permeability terrains, century-scale evolution of regulated rivers, and the form and function of headwater channels.

Evolution of high permeability terrains: The youngest portions of Oregon’s High Cascades have almost no surface water, because all water infiltrates into high permeability lava flows. Yet on older parts of the landscape, streams are abundant and have effectively eroded through the volcanic topography. In a paper in Earth Surface Processes and Landforms (Jefferson et al., 2010), I showed that this landscape evolution was accompanied and facilitated by a hydrologic evolution from geomorphically-ineffective stable, groundwater-fed hydrographs to flashy, runoff-dominated hydrographs. This coevolutionary sequence suggests that permeability may be an important control on the geomorphic character of a watershed.

Human and hydrologic influences on large river channels: Almost all large rivers in the developed world are profoundly affected by dams, which can alter the hydrologic regime by suppressing floods, supplementing low flows, and raising water levels in reservoirs. On the Upper Mississippi River, in the 70 years since dam construction, some parts of the river have lost islands, and with them habitat diversity, while in other areas new islands are emerging. In 2008-2009, I had a small grant that facilitated the examination of some islands with a unique, unpublished long-term topography dataset and its correlation with hydrologic patterns and human activities. This project became the thesis research of one of my graduate students, who will be defending his M.S. in May 2010.

Headwater channel form and function: Although headwater streams constitute 50-70% of stream length, the geomorphic processes that control their form and function are poorly understood. Most recent research on geomorphology of headwater streams has focused on streams in very steep landscapes, where debris flows and other mass wasting processes can have significant effects on channel geometry. In the Carolina Piedmont, gentle relief allows me to investigate the formation and function headwater channel networks, isolated from mass wasting processes. One of my graduate students has collected an extensive sediment size distribution dataset which shows that, at watershed areas <3 km2, downstream coarsening of sediment is more prevalent than the downstream fining widely observed in larger channels. Another graduate student is collecting data on channel head locations and flow recurrence and sediment transport in ephemeral channels in order to sort out the relative influences of topography, geology, and legacy land use effects on the uppermost reaches of headwater streams. Both of these projects have already resulted in presentations at GSA meetings.

Whew. So that’s what I do, between teaching some field-intensive courses and raising a preschooler. But, what am I? Hydrologist? Geomorphologist? Hydrophillic geologist? Or something else entirely?