The Vigil Network: Preservation and access of data

Part C

TABLES BY W. W. EMMBTT and R. F. HADLEY

In the United States the recognition of a deficiency in detailed data on hydrologic and geomorphic processes led to the idea of establishing a network of small drainage basins and other selected sites where observations of basic processes would be made over long periods of time (Leopold, 1962a). The network of observational areas has been named the Vigil Network (Leopold, 1962b). Publications on this concept of relatively simple observations of landscape (Emmett, 1965; Hadley, 1965; Hadley and Lusby, 1967; Leopold and Emmett, 1965; Miller and Leopold, 1963) have included suggestions for installation, maintenance, and techniques of observation.

It is hoped that the Vigil Network can serve as a nucleus for international cooperation in hydrology especially in long-term programs of landscape observations. At the first session of the Coordinating Council for the International Hydrological Decade held May 24- June 3, 1965, at UNESCO House in Paris, France, Vigil basins were recognized as one of the Decade projects for collection of basic data (UNESCO, 1965, p. 10-11). The Coordinating Council considers Vigil basins as a special kind in UNESCO's classification of experimental and representative basins. In addition to the 58 Vigil Network sites established in the United States (Hadley, 1965), there are several sites on other continents which help to encompass the wide variety of landscapes and environments of the world.

One of the principal objectives of the Vigil Network is to preserve the results of the field measurements for future generations of scientists. This paper presents the plan for filing the data from Vigil Network sites in a uniform manner in the designated repositories. The appendix of this paper is a sample copy of a file which has actually been submitted to the repositories. This particular sample is a more complete version of the data which Leopold and Emmett (1965) used to illustrate the need for establishing the repositories. The location of repositories is discussed later in this paper.

In a file deposited in the international repositories, the description of the site location and the permanent bench marks installed should be explicit so that subsequent investigators can find the field location with a minimum of effort. The format of the data of the original survey should be similar to that suggested in this paper. For resurveys, if data collected before a file has been submitted to the repositories fall within the guidelines suggested below, this data should be included to allow a comparison of the first survey with later ones. After the file has been deposited, only data meeting the requirements discussed below should be submitted to the repositories.

The site location can best be described by a tabulated roadlog of distances using permanently identifiable features as beginning and intermediate references. As an example, the description by Leopold and Emmett (1965, p.

14) or on page 11 in the appendix of this

report should enable any observer to reach that site. A location sketch map, or a topographic map if one is available, is also helpful to a new observer in relocating the site. In addition, a topographic map allows the observer to be preaware of some of the physical characteristics of the area. However, to minimize the bulk of the folders a page-size cutout or photocopy of the pertinent area within the topographic map sheet may suffice. If plane-table or other survey maps are made, they should be included if they can be conveniently reproduced to fit the file-folder dimensions. However, care must be taken not to reduce a map so much that legibility of the map and its explanations are affected. Even simple sketch maps of the area are handy to the fieldman in relocating bench marks and are appropriate for inclusion in the file.

The file should include a physical description of the site, consisting of data on the geology, soils, vegetation, climate, and topography. The reasons for choosing the area for the particular long-term measurements should also be given.

Ground photographs of pertinent views may be included, but must be adequately identified by the position of the camera and the date of the photograph. If the film negative is on file and available for loan, its location and means of borrowing should be detailed.

Most important is the inclusion of data sheets which show the bench-mark elevations and the initial surveys. Resurveys made before a file is submitted to the repositories may be included if they do not materially add to the bulk of the file. However, data from resurveys that indicate a definite trend or reversal in trend should be included even if they constitute several additional tables. To standardize the format for presenting such data, the next section of this paper shows suggested table headings for the more common types of observations. The units for the data may be either metric or English and should preferably be the units principally used in the country of the station. Within a file the units should be consistent.

After the file has been deposited in the repositories, subsequent data, photographs, or maps of resurveys should be submitted only if they show an important trend or change in the trend indicated by the data initially filed. This practice is to minimize maintenance efforts at the repositories and to keep individual files from becoming unnecessarily bulky with repetitious data.

Publications which relate to the studied area should be referenced in the file, but copies of the publications need not be included. References should be submitted to the repositories for publications issued after the date of filing.

A card index is available at each repository to facilitate retrieval of data on file. Details of submitting index cards with each file folder are discussed later in this paper.

Some observations made in the field by individual investigators are of a nonpermanent or short-term nature for example, mass-movement observations on hillslopes using wooden dowels or glass beads (Hadley and Branson, 1965)and, in stream channels, the use of scour chains or painted rocks for channel-scour and particle-transport studies. If data of nonpermanent installations show significant results, however, they should be included in the repository file for the period of their collection provided that permanent bench marks are established in the basin. If possible, the locations of original bench marks should be detailed or shown on maps, so a later investigator can closely match the location of his measurements to that of the original measurements. The data can thus be used at a later time to compare results of similar studies for two periods even though the original installations cannot be exactly located or recovered. Data from sites having only nonpermanent installations should not be submitted to the repositories.

Observations of stream channels and valley floors are usually conducted by surveying pro* files between permanently established bench marks. Thus, these bench marks must be adequately described and identifiable in the field. Commonly, a small metal tag may be affixed to the bench mark which describes the bench mark and its elevation. In instances where bench marks do not protrude above the ground surface or are otherwise not easily found, a triangulation net extending from easily identifiable features should be included so that bench marks may be relocated. On long profiles extending more than 300 feet (or 100 m), intermediate bench marks should be established so that the stationing of resurveys con be maintained identical to that of the initial survey. Also, longitudinal profiles are assumed to be along the stream thalweg unless specified differently. For cross-sectional surveys, it is standard practice to present the data from the left-bank (looking downstream) bench mark to the right-bank bench mark.

The following skeleton tables (tables 1-3) are examples showing location of stream-channel cross sections and long-profile data. These tables are merely illustrative, and the data shown are by no means complete.

As previously mentioned, some types of observations are of a temporary nature, and the possibility of relocating them in the future is slight. However, if a significant shortrterm record is available at the time of filing with the repositories, they may be included to allow a comparison with later surveys even if reestablishment of the installation is necessary at the later survey. The initial investigator can decide whether or not these types of data should be included in the file. The following (tables 4-7) are suggested formats for several types of short-term measurements that are used in stream-channel and valley-floor observations.

The erosion of the surficial mantle on hillslopes with the resulting changes in profile shape, whether it be by subaerial erosion or mass movement, is often subtle; therefore, monitoring of hillslope profile over long periods has been neglected. Such observations need to be made in a variety of both climatic and lithologic environments to establish cause and effect relationships.

The data for hillslope observations to be placed in the repository files must include original surveys with location of permanent survey bench marks. The format of the following skeleton table is suggested.

Because of the possibility of mas® movement on hillslopes, more than one bench mark should be installed at each site to increase the accuracy in checking the elevation and position of markers as originally established.

There are types of observations in addition to hillslope profiles that furnish useful data on the erosion of landscapes. Although many of these observations do not lend themselves to standardized tabulation, they should be included in the repository file. Some of the types of observations being made are briefly summarized as an example.

The use of erosion pins or nails and washers to measure surficial erosion has proved to be a good supplement to profile surveys. The installation of erosion pins or nails, however, is a technique that requires annual maintenance and at best is subject to deterioration by rust and trampling by livestock. Therefore, the inclusion of erosion-pin data should be only a supplement to instrument surveys (see tables 15-16, appendix). Another point of caution is that erosion pins may be subject to heaving by frost action. Also, hillslopes composed of swelling clays can puff up and give negative exposure measurement after a period of alternate freezing and thawing. Therefore, repeat surveys in this type of material should always be made at the same time of the year.

The use of small reservoirs on Vigil basins have proved very useful in studies of runoff and sediment yield and their relation to geomorphic characteristics. There are, however, some limitations that must be considered before choosing a reservoir as an observation station. The reservoir capacity-drainage area ratio should be sufficiently large to insure against spill during a flood having a recurrence interval of 50 years. This requirement allows direct measurement of runoff and sediment yield from the basin without estimating the volume of spill of both water and sediment. It should also improve the correlation of runoff and sediment yields with basin characteristics.

The following table formats (tables 9-10) for reservoir cross-section surveys and runoff and sediment yields should furnish adequate data for the repository file folder. In addition, a plan map or sketch of the reservoir showing location of bench marks and cross sections should accompany the data.

If a Vigil station is near a meteorological station, the detailed climatological data can be used to supplement observations. However, most Vigil stations are in remote areas where precipitation data are scarce, particularly data on rainfall intensities. The minimum requirement should be a storage gage, charged with oil to reduce evaporation, where seasonal or annual precipitation can be measured. The suggested table (table 11) should be included in the repository file folder.

Vegetation measurements and descriptions are essential for the extrapolation of results of hydrological studies. Of the hundreds of methods that have been used to measure vegetation, the ones that measure areal coverage and weight or volume are the most meaningful in hydrologic studies. In addition to live vegetation, soil-surface features such as quantities of mulch or litter, bare soil, and rock should be measured.

The point quadrat method (Levy and Madden, 1933) can be used to measure foliage cover of herbs and low shrubs. For hydrological studies it is suggested that only the first hit as pins are pushed toward the soil surface be recorded. This method permits calculation, from tabulated data (table 12), of percentage cover per species and percentage of soil surface occupied by mulch or litter, rock, and bare soil. For calculation of foliage volumes the height of each plant unit should be measured and recorded. For measurement of possible vegetation changes over time, permanent metal stakes should be installed 100 feet (SO m) apart.

The permanent 100-foot transect suggested above may be used as one edge of a rectangular plot for sampling woody species (Canfield, 1941). For each woody plant the length of the tape covered by live foliage should be recorded. For trees and large shrubs the depth of crown or foliage should also be recorded, and for both trees and shrubs heights should be recorded.

Arrangements have been completed with two organizations to serve as permanent repositories for basic data on Vigil Network sites. The two permanent repositories will be the Library, U.S. Geological Survey, Washington, D.C., U.S.A., and the Library, Laboratory of Geomorphology, University of Uppsala, Uppsala, Sweden. It is anticipated that an eastern European country will soon make available facilties to establish a third repository.

The purpose of these permanent repositories is to prevent loss of data by neglect, fire, or other causes and to give scientists easy access to the data. The repositories will enable scientists to find field locations where observations of geomorphic processes over time are being made. Several procedures and data arrangements are suggested in this paper so that data can be submitted in standardized format. One benefit of standardization is that the material to be sent to the repositories can be prepared in a very simple fashion. The principal items include written descriptions and maps which will allow a person to find bench marks in the field. In addition, at least the original set of data taken at each observation point is tabulated so that future researchers will know the initial field conditions.

Data for each study site will be placed in a folder and kept on file in the repositories. A card index file will be provided so that a visitor can look up which investigators and what areas are represented in the filed material. Investigators are requested to fill out the form in the pocket of this report to facilitate the task of entering information on crossindexing cards in a uniform manner. Card number and type should be left blank, and the date is date of sufomittal. One copy of the index card should be included with each file folder. Another copy should be sent to R. F. Hadley, coordinator of Vigil Network activities in the United States (address shown on p. 7).

Both repositories are ready to receive material for permanent filing. Scientists are urged to prepare their data in the manner suggested in this paper, and to submit one copy to each

Dec* 1. 1967

Last Day Gully is an example of a small ephemeral basin which has alternately degraded and aggraded in post-Pleistocene time, presumably in response to changes in climate. It terminates in a small alluvial fan on top of a 15-foot alluvial terrace in the valley of the Popo Agie River. The planimetric map of figure 1 illustrates the general configuration of Last Day Gully.

Because similar gullies in small basins are common and because their visual aspect alone does not indicate whether in the present climate these gullies are aggrading, stable, or degrading, this one was chosen for long-term observation as part of the Vigil Network.

This site is an ephemeral wash, or gully, about 1 mile northeast of Hudson, Wyo., NW */4 sec. 6, T. 2 S., R. 3 E. (lat 42°55'33" N., long 108°34'19" W.). It is included on the topographic maps published by the U.S. Geological Survey entitled "Hudson, Wyo.," scale 1:24,000 and "Lander, Wyo.," scale 1:250,000 (parts of both appear in this folder, figs. 2-3). The main channel extends about 3,400 feet from the watershed divide to its end. The gully terminates in a semicircular alluvial fan. The gully bed is sandy silt and nearly free of vegetation. Vegetation adjacent to the channel consists of a mixture of low shrubs and grasses. Predominant shrubs are sagebrush (Artemisia tridentata Nutt.) and cactuses (Opuntia spp.). Grasses generally belong to the grama species (Bouteloua). Total vegetation cover varies but averages about 30-35 percent. The total area within the watershed is about 55 acres. The average elevation is 5,150 feet above sea level, and the relief between the watershed divide and the alluvial fan is 142 feet. Precipitation averages about 10 inches per year.

To reach the site of Last Day Gully, one may start at the center of the village of Hudson, Wyo. (see Hudson, Wyo., 1:24,000 topographic map, fig. 2), proceed east on State Highway 789 for three-quarters of a mile, and then turn north onto an unimproved side road. This road becomes a one-lane steel bridge crossing the Popo Agie River 200 yards from the junction with State Highway 789. After crossing the bridge one proceeds about 700 yards, leaves his automobile, and walks westerly along a fence, bearing N. 20° E. At a distance of 400 feet along the fence is the mouth of Last Day Gully, where the channel terminates in a lowangle fan. The alluvial fan and fence line are indicated in the upper left of the enclosed planimetric map of Last Day Gully (fig. 1). The permanent reference points along the stream, consisting of 1/2-inch diameter steel rods driven in the ground and protruding about 6 inches above the ground surface, are noted on the map by a -small solid dot at each end of the lines marking the cross sections.

The principal measurements consist of 16 cross-channel land-surface profiles surveyed at locations specified in table 1 of this file (p.

17) and are also shown on the planimetric

map (fig. 1). At the time of preparation of this file, four field surveys had been made; August 6-8, 1962, June 9-10, 1963, July 26, 1965, and June 18, 1966. Elevation® from these surveys are listed in the next series of tables (tables 2-17). In addition to having bench marks, two of the cross sections were instrumented with 10-inch-l'ong steel pins driven into the ground at given locations (sections A-B and E-D). Values of erosion can be determined accurately at 'these pins and are given in the tables for sections, A-B and E-D in lieu of elevations from annual resurveys (tables 15- 16). It is emphasized that these 10-inch-long

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