Definitions of Landslide Features

I have spent a lot of time lately learning about mass wasting. No, that doesn’t have anything to do with drugs. Mass wasting is the downslope movement of slope material under the influence of gravity. Mass wasting shows up as rock falls, landslides, and various types of flow (mud flow, earthflow, debris flows, etc.). I am reproducing here a table from a handout that I got in a recent lecture on landslides. The handout has on it a hand-written reference to Turner & Schuster (eds) 1996, Landslides: Investigation & Mitigation.  On closer examination, an almost identical table can be found at the wikipedia entry for Landslide Clasification.  The wikipedia version, attributed to Varnes (1978), Cruden and Varnes (1996), Hutchinson (1988), and Hungr et al. (2001), is given below.

Type of movement Type of material
Bedrock Engineering soils
Predominantly fine Predominantly coarse
Falls Rockfall Earth fall Debris fall
Topples Rock topple Earth topple Debris topple
Slides Rotational Rock slump Earth slump Debris slump
Translational Few units Rock block slide Earth block slide Debris block slide
Many units Rock slide Earth slide Debris slide
Lateral spreads Rock spread Earth spread Debris spread
Flows Rock flow Earth flow Debris flow
Rock avalanche Debris avalanche
(Deep creep) (Soil creep)
Complex and compound Combination in time and/or space of two or more principal types of movement

The Geographic Realm

Some thoughts from a lecture at school today:

We break the world into arbitrary units of Natural and Cultural. The University is broken up this way, with its College of Science and its College of Humanities, and never the two shall meet. As geographers we know that the two, Natural and Cultural, are really interwoven. At the interface between Natural and Cultural, the two arbitrary units are so twisted and tied together that the attributes of one become the attributes of the other. It is at this interface that Geography occurs

Dot Grid Method

The area of a surface with square corners and straight edges on a map or photo can be found by multiplying the length of the surface by its width and then converting to real-world units using the scale of the image. What do you do if you need to find the area of an organic shape, or of a very complex geometric shape? One method that is widely used is the dot count using a dot grid.

dotgridA dot grid is a transparent sheet printed or drawn with dots arranged in a regular and even pattern such as a grid. When the dot grid is calibrated to the scale of the map or photo you are studying (finding the number of dots that falls in a known area), the area of an unknown surface can be found by laying the dot grid over the area, counting the number of dots that fall in and on the surface, and dividing that number by the number of calibrated dots per unit area. This gives you the area of the surface you are estimating in the units of your calibration.

As an example, let us suppose that I have calibrated my dot grid on an aerial photograph using a farmer’s field, bounded by section-line roads, as my known distance. How do I know the area of the farmer’s field? Often, fields are laid out along the US Public Land Survey System, with roads following the 1-mile edges of sections. A field bounded by such roads would be 1 square mile. These human features are obvious in aerial photos and on maps, and are very useful for establishing scale and for calibrating dot and square grids. Calibrating against the 1-square-mile field, suppose that I find that my dot grid is a size that there are 225 dots per square mile.

Now suppose that I have to find the surface area of a lake on the same photograph as the 1-square-mile field. Using the dot grid that I have just calibrated, I cover the lake with the dot grid and count 675 dots on the lake. The number of dots in my area-for-estimation (675), divided by my number of dots per unit area (225 dots per mile square) gives the lake an area of 3 square miles.

There are a few key points to using the dot grid:

1.) A dot count is a statistical method. It is important that you don’t line up the grid to get the best fit to count in your object. The whole point of the dot count is to see how many dots randomly fall within the area when the dot grid is placed in a random relationship to the area.

2.) When you are counting dots, each dot that falls completely within the area is given the weight of 1 full dot. Any dot that touches the side of the object, whether it is inside, outside, or one the line, gets a weight of 1 half dot. The number of whole dots plus the number of half dots (or the number of half dots divided by two, actually) is the total number of dots to be used in estimating the area of a surface.

3.) Once you have begun counting dots, don’t move the dot grid. If you do accidental move the grid, don’t just keep counting. You have to start over from the beginning.

I have created a dot grid for you to use in trying this method out. To use the dot grid, click on the image above to download “dotgrid1.pdf.” This file needs to be printed on plastic transparency, which is available for inkjet and laser printers, as well as copy machines for between $0.15 and $0.75.

Desirable Watershed Conditions

The capture, storage, and beneficial release of water.
The Watershed Manager’s Mantra

To achieve the watershed manager’s goal of capturing, storing, and releasing water in a safe and beneficial way, he must:

  1. Maintain vegetation on the site sufficient for absorbing the energy of precipitation (so raindrops hit leaves and dissipate their energy – raindrops splatter soil, but they also plug pore spaces, which lowers infiltration, and increases runoff, which means an increase in erosive potential.).  *Enhances infiltration
    • (organic soil has higher infiltration) *Vegetation delays movement of water toward and into drainage pathways.  1in rainfal on 1ac exerts 900ft-tons of energy.
    • Increasing velocity increases the capacity of water to do erosive work.
    • A slower raindrop has much more time to infiltrate.
    • The more water that plants absorb, the less water to run over the surface.  Less surface water equals less erosion.
  2. Maintain minimal drainage density.  The higher the drainage density, the better the drainage (more risk of flash flooding, water leaves the system quicker).  Achieve highest possible sinuosity.
  3. Optimize temporary water storage.

GIS Links

Here is the second installment from my Favorites folder. This time I’m looking through the folder of GIS links. I guess it’s been quite a long time since I’ve looked through these links and cleaned them out, because there are millions of them (not really), and some of them are worthless.

As a little disclaimer, since I live and work in Washington State, a lot of my data links are for Washington State. Sorry to all of you looking for stuff on, say, Zimbabwe, or something. The links are split up by general topic, but I haven’t put them in any further order than that. Hopefully I will eventually annotate all of these, so that you don’t have to visit them to see exactly what they are, and to give you some idea how good the sites are.

Free Geospatial Data

Washington State Maps at University of Washington Libraries (09/09/05)

ArcData Downloader (09/09/05)

Washington State DOQs and DOQQs (09/12/05)

Washington DNR GIS Data (09/12/05)

Free GIS Data (09/12/05)

StreamNet Salmon and Stream Data (09/12/05)

USGS GISDATA Map Studio (09/12/05)

Landsat Imagery Data Access (09/12/05)

NGDC GLOBE Project (09/12/05)

GTOPO30 Global Topographic Data (09/12/05)

Washington State DRGs (09/12/05)

HYDRO1k North America Data Page (09/12/05)

National Atlas Raw Data (09/12/05)

Mount Saint Helens DEMs (09/12/05)

Pacific Northwest Biological Geospatial Coverages (09/12/05)

Inside Idaho GIS Data (09/12/05)

USGS Seamless Data Distribution

Guide to Mostly On-Line and Mostly Free U.S. Geospatial and Attribute Data (09/12/05)

Northwest Subbasin Geographic Data Browser Home Page (09/12/05)

UA Census 2000 TIGER/Line Files (09/12/05)

USGS Geographic Data Download (09/12/05)

3D Visualization Software (Free and Otherwise)

3DEM Downloads (09/09/05)

GIS Software (Free and Otherwise)

Map Maker – Desktop Mapping (09/12/05)

Free GIS and CAD Software (09/12/05)

GIS Knoppix (09/12/05)

FreeGIS Database (09/12/05)

Jump Unified Mapping Platform (09/12/05)

GIS Tutorials

DRG Tutorial (09/12/05)

Environmental Applications of GIS (09/12/05)

Minnesota DNR GIS/GPS Training Materials (09/12/05)

LandSat Tutorial (09/12/05)

Citizen’s Guide to Spatial Data and NSDI (09/12/05)

Mt. Rainier Challenge: Superior Overlays using 3DEM (09/12/05)

The Remote Sensing Tutorial (09/12/05)

Scale, Accuracy, and Resolution in GIS (09/12/05)

Making a Map (09/12/05)


ArcPad Evaluation (09/12/05)

ArcVoyager (09/12/05)

ArcView Tutorials

Columbia River Basin Environmental Research Project Curriculum (09/09/05)

Introduction to ArcView GIS 3.x (09/09/05)

ArcView Tips and Tutorials (09/09/05)

PASDA’s ArcView Tutorial (09/12/05)

Preparing tables for use with ArcView and ArcGIS (09/12/05)

ArcUser Magazine (09/12/05)

Terrain Modeling with ArcView GIS (09/12/05)

ArcView Scripts and Extensions

ArcView Scripts Downloads (09/09/05)

Image-Tools (v2.6) and DRG-Tools (v3.7) (09/09/05)

Minnesota DNR ArcView Extensions (09/09/05)

Impervious Surface Analysis Tool (09/09/05)

Polygon in Polygon Analysis (09/12/05)

Watershed Delineation Extension (09/12/05)

GIS Fonts (09/12/05)

ShadeMax Color System (09/12/05)

BASINS: Better Assessment Science Integrating Point & Nonpoint Sources (09/12/05)

GIS Information Portal

Web Resources Compiled For Terrain Modeling (09/12/05)

Digital Grove (09/12/05)

Open-Source GIS (09/12/05)


In Search of a Better Scraper

One of my main pedological field tools (pedology is the science of dirt), other than my trusty shovel, is the “scraper.”  The search for the perfect scraper is the focus of all my gear-hunting efforts.  The scraper is used when looking at a soil profile to get a clean, flat, clear soil face to look at.  I have tried, or seen tried as scrapers: old army shovels; the head of a Pulaski firefighting tool on a shorter handle, like a hammer handle; garden hoes; garden trowels; masonry trowels; barbeque spatula; and an ice scraper.  I even used a pie knife for a while.  The very best scraper tool I have used, though, and perhaps the most widely used and deeply loved, is a pointed Marshalltown Trowel.

Global Earth Observing System of Systems

It must be going on a couple of years now that we have been getting e-mails at work talking about GEOSS, a new “system of systems” that will somehow greatly increase our knowledge about the Earth, but it wasn’t until just a few days ago that the real importance of the project hit me.  I got so excited about the whole thing that I wanted to write an article about it, but realized that I couldn’t really remember any of the specifics about the system from the few years of half-read e-mail.  An EPA document helped supply the facts that I haven’t really been paying attention to over the last couple of years.

GEOSS, which stands for Global Earth Observing System of Systems, is an attempt to “connect the dots” between thousands of individual pieces of technology that are gathering earth observations around the globe.  The global initiative is spearheaded by the United States, through the Group on Earth Observations, and supported by sixty countries, the European Commission and more than 40 international organizations.  NOAA’s Earth Observing System Web page, in speaking of GEOSS, asks us to “imagine a world in which we can forecast winter weather months in advance; predict where the next outbreak of malaria, SARS or West Nile virus is likely to hit; and, in the U.S. alone, reduce energy costs by about $1 billion annually.”

Of the system, EPA Administrator Mike Leavitt said, “Our environment knows no boundaries. We all breathe the same air and drink the same water. We all cause pollution—every one of us. And working together, we can find the solutions and affect the changes needed to protect people, promote prosperity and preserve our planet,”

I don’t think I quite understood the significance of GEOSS, and I still probably don’t realize it fully, but I see GEOSS as something like the Google of Earth data.  It is the very discontinuity of data about the Earth’s systems that causes so much contention in making policy and management decisions.  We don’t know exactly how to fix the Earth’s problems when we don’t exactly know, from our fractured data, what the Earth’s problems are, or even if it really has any.  GEOSS represents an opportunity to finally get a whole snapshot of the Earth’s health. I am so excited.


I will post more about GEOSS as I know more.