Nichols, K. K. and Bierman, P. R., Fifty-four years of ephemeral channel

response to intense military activity at Camp Iron Mountain, Mojave

Desert, California

The authors surveyed in great detail several tracts of land on a

desert piedmont surface to assess any lingering geomorphic effects from

two years of intense military training 55 years ago. Their data suggest

that the shallow ephemeral channels common to this area were disturbed at

the onset of military training and have still not regained their

pre-disturbance character. In particular, channel widths, depths,

cross-sectional areas, drainage densities, and areas remain different in

disturbed plots of land as compared with control plots.

The authors present convincing evidence that the effects of

military training 55 years ago linger today, and will likely persist into

the future. The writing is clear and concise, with only a few grammatical

errors as noted. The diagrams are helpful and easy to understand, with a

minor exception or two (again, noted on the manuscript). Their data appear

to be thoroughly collected and thoughtfully analyzed, although the

standard deviations of channel measurements commonly approach 75% of the

mean value, and often overlap with the standard deviations of measurements

that the authors mean to distinguish. Therefore, although the differences

in channel character are distinguishable, they are often small.

I recommend this paper for publication with the revisions noted.

These suggestions mostly concern grammar and punctuation, and are noted on

the manuscript. My comments for major revisions or further thought are

provided below, and are referenced by number to their location of concern

in the manuscript.

1. The word "plots" is used lots in this paper. It would help to

define this term not solely with respect to the different varieties of

experimental types of plots you used for this study. A brief statement in

the methods section that makes clear their designation for a tract of land

of a certain size would help the reader.

2. Although the title clearly states that the focus of study is the

nature of ephemeral channel response to military training, the

introduction states the importance of a broad understanding of geomorphic

disturbance and response to military exercises. Some explanation, then,

should be given for the focus solely on channel character in this study.

What other geomorphic disturbances occur as a result of military training?

Why is the channel character of paramount importance here? For example,

soil compaction and surface smoothing are discussed later in this paper.

Some mention early in the paper that they and any other effects result

from military training would improve the paper.

3. Might these categories of plots introduce any kind of bias to the

data? The paper would be improved by an explanation for why plots were

divided into these three categories for this study. We can only assume

that the remains of the camp may be similarly divided (visually).

Review of Nichols and Bierman

This paper outlines the effects of military activity from 1942 to 1944 on

the channel morphology of a desert piedmont surface in the Mojave Desert

of California. The study has compared three different types of land use

at the Army camp in order to determine the effects of each type of

activity: walkways, roads, and control sites that were untouched by camp

activities. It is shown that the natural channel system on the piedmont

slope has largely been unable to reestablish itself within the military

camp area. Walkways, which had been outlined by small rock walls, have

diverted water flow on the piedmont surface causing channels to be

narrower and shallower than natural channels in the control areas.

Walkway channels also tend to be discontinuous and have a high drainage

density. Road berms have also redirected water flow on the piedmont

surface, creating a 20-40m zone of sheetwash down gradient of the berm

with most runoff dispersing into braided channels at breached berms or

along roads that are parallel to gradient. Increased stream power,

discharge and sediment yields have resulted from the compaction and

smoothing of soil on the piedmont surface. Nichols and Bierman suggest

that removal of road berms and walkway rocks would aid the rehabilitation

of piedmont channels, although the consequences of soil compaction and

smoothing may last for tens of years.

In general, I found the paper to be very well thought out and clearly

presented. Methods are carefully reviewed, and the data is presented both

verbally and visually to aid reader comprehension. The data correlate

well with the reported field observations and final conclusions. All

calculations are presented with their corresponding equation sets and

error margins. The writing was well-organized and easy to follow. Some

parts of the paper were a bit choppy and/or redundant, however, I believe

that some minor edits could resolve that problem. Also, some details

could be better explained (see manuscript notes). Tables and figures were

clear and straightforward - I was able to quickly gather information from

most of the tables and figures. Only one figure seemed out of place and

unexplained in the text (note #9 in the manuscript). A few typos are

present throughout the script.

I would recommend this paper for acceptance with only minor edits. The

paper presents timely evidence for the effects of human impact on

landscape development and provides information that will assist in future

remediation of such sites. I feel that the topic will be of interest to a

large audience. Additionally, it is a strong paper with a clear portrayal

of current channel activities at Camp Iron Mountain, and is written with

an attention to detail and a clarity that makes it accessible to readers

from a diversity of scientific backgrounds. The data sets are complete

and well represented in the accompanying tables and figures.

Manuscript:

1. I think this sentence would work better as a beginning sentence - i.e

as the first sentence of the paragraph. It's a strong sentence that would

make a good impact at the beginning of the paragraph.

2. I just wondered why the army had constructed the berms and walkway

outlines - was it for navigation only, or to also divert channel drainages

away from the camp?

3. In this paragraph, you say that most of the precipitation is being

infiltrated, then in the last sentence you say that only some of the

overland flow is being infiltrated. I find that a bit confusing.

4. How deep does sheetwash generally need to be to prevent incipient

channels from being obliterated by raindrops?

5. I just wanted to mention that I switched 'training' to 'usage' because

it sounded like the stream had undergone military training. Also, the

hanging "54 years ago" at the end of the sentence seems very out of place,

although I don't know how to better rewrite that.

6. You haven't mentioned anything about the size or area of the study

plots - do they all have the same area?

Also, it might be helpful to the reader to mention an average channel

width for control streams, since you mention the depth several times.

A more thorough explanation of why the plots were chosen as they were

would be helpful. It is obvious that you went through a lot of effort to

standardize the plots, but what was the basis for those standards? For

example, why did all of the road plots need to be free of rock alignments?

Was it to be able to view the effect of each type of structure alone? If

so, then say it!

7. Figure 3 - I don't understand what "abundance" represents.

8. "The average drainage density for the walkways inside the walkway

plots..." I'm confused - do you mean the density of streams that have

formed within old walkways? And does that mean you are ignoring any

streams that are in the plot but did not form in walkways for this

calculation?

9. How does Figure 5 fit into the text here? You don't discuss it at all.

10. On page 8 you say that the control plot stream channels have the

largest range of orientations, but here on page 9 you say that they have

little deviance in orientations. So which one is it?

11. The underlined sentence seems out of place since the previous

sentence discusses the rock barricades. It might be best to start a new

paragraph here, using the underlined sentence as the first in the new

paragraph.

General note: I had a hard time visualizing how road berms were affecting

channel flow from reading the text.

The paper by Nichols and Bierman presents survey data gathered in and near a military camp abandoned over 50 years ago. The data characterize the small-scale drainage network and demonstrate that human impacts on the landscape can still be detected in measurements of average channel width, depth, area, and drainage density.

Overall, the paper is complete and reasonable presented. It would be greatly strengthened by the addition of statistical verification of population seperability. The process model section could be condensed as it is repetitive of the text in places. The text needs minor clean-up including correction of the page 1/page 2 transition and line spacing. There are numerous minor marginal comments on the ms.

Final recommendation, publication after revision.

1. Title needs a time reference so as to indicate activity is not ongoing.

2. No sense at end of page 1.

3. On figure 1, need to show camp.

4. Figure 1A needs lat., long, and scale.

5. This sentence is the place to introduce, succinctly, the test of means difference using t-test.

6. Condense to one sentence, these are redundant.

Critical Review of Nichols, "Fifty-four years of ephemeral channel response to intense military activity at Camp Iron Mountain, Mojave Desert, California."

Nichols "Fifty-four years" describes the affects of the U.S. Army's presence in Camp Iron Mountain (Mojave Desert, CA) on the re-establishment of ephemeral channels fifty years after the camp was abandoned. Nichols studied three types of plots including two types of experimental plots (road and walkway) and a set of control plots. The military's presence and alteration of the landscape has not allowed the ephemeral channel network to fully recover to 'natural conditions' (as illustrated by comparison of control and experimental plot data). Channel depths and widths are smaller in experimental plots and the channels are more discontinuous than control plots channels. Control plots have the highest drainage densities. Local drainage divides set in place by the military, such as rock alignments and road berms, have changed channel flow patterns in experimental plots forcing flow against the natural gradient and leaving areas 20-40m without channeled drainage. Nichols also explains the results of previous studies that focused on humans (military and ORVs) smoothing surface roughness, reducing infiltration, and compacting desert soil. Nichols links existing data to his findings by showing that these factors are present in the experimental plots due to the presence of the military. Nichols shows that these factors also influence the discrepancy between control and experimental plots.

Nichols thoroughly explains how he collected the data, presents the data clearly, and provides logical explanations about the data. Nichols seems to have a sufficient amount of data (i.e. topo points, plot numbers, and variation in plot locations) to make generalized conclusions about the entire camp. The control plot data, even with a large variation in location on the piedmont, supports that the piedmont is uniform (and therefore a 'true' control). Nichols backs up his general conceptual interpretations by citing well known, reliable sources in geomorphology (Horton, Dunne and Leopold). Nichols also cites more recent source that have studied the affects of humans in arid regions and links these sources to his study. Nichols illustrations complement the data and explanations well. The rose diagram of channel orientations is a very strong figure! The air-photo of plot locations also sets a lot of things in perspective. I do have a few recommendations for figures, which are listed below.

I believe that Nichols paper should be accepted for publication simply because it is an original study conducted in unique area where the military's impact on small-scale geomorphology can be studied. Not only does Nichols have an interesting data set, but he also does a good job of explaining of how the military has affected the recovery of the channel network. I do recommend this paper (in its current form) for publication, however I am not sure what the editors of Environmental and Engineering Geology Impacts on Military Operations are looking at for publishable work. Nichols does not explain why the military should care (or why anyone should care) about what persisting affects that Camp Iron Mountain has caused to the recovery of the channel network. I can understand that the presence of the camp has altered the channel network morphology (which is interesting, hence making the paper worthy for publication somewhere), but does that have far-reaching implications that the editors of Env. and Eng. Geology Impacts on Military Operations will be concerned with.

Specific Comments:

1. Add specific data/numbers here You use numbers elsewhere in your abstract, it will make it more consistent.

2. This refers to Figure 1B. You mention the camp in the text yet it does not appear on figure 1B you could add it by just drawing a square on the existing figure. It will help to further place fig 1C into perspective and to explain how the camp roads are placed sub-parallel/perpendicular to the natural gradient.

3. This is the point in the paper when I noticed that you jumped between the uses of runoff and overland flow. Do they have the same meaning? In the next paragraph you explain sheetwash this helps, but define/differentiate between runoff and overland flow.

4. Mention that a computer contoured the data and mention the program software I think Surfer is known as one of the best for interpolating topography.

5. Would measuring two channel orientations for channels with curvature make any sense or is averaging the orientation the way to do it. I feel that measuring two (or three) orientations might better represent what is really happening.

6. This refers to figure 3. Is there any significance to the fact that all the plots are skewed to the right?

7. In your Data Section (under channel orientations) you mention control plots have the largest range of orientations, yet here you mention there is 'little deviance'. You should reword this a little bit to make it sound less contradicting. And also mention that the control plot channel orientation is very close to the piedmont average gradient the connection is not spelled out in the text and I think it is an important one.

8. How did you estimate that 'more than half of the road berms and walkway alignments are still intact'. I'm a little confused here have half of these disappeared in fifty years?

*** Two general comments. 1. Mention the previous studies on surface roughness and soil compaction earlier (in the intro) the first mention of these results comes on the 9th page. The text will flow better if you mention these (just briefly) studies earlier in the paper. 2. Mention that over ten other camps existed in the Mojave that all are probably experiencing the same implications by having road berms and rock alignments present.

"Fifty-four years of ephemeral channel response..." by Kyle

Nichols discusses the recovery (or lack thereof) of desert surfaces

following a short-term, intense disturbance of the landscape caused by

military manuevers during World War II. The surfaces in question are a

bank of coalescing alluvial fans forming a piedmont surface in front of

the Iron and Granite Mountain ranges in the Mojave Desert. Specifically,

Nichols looked at the size, distribution, and orientation of shallow

ephemeral streams in both disturbed (containing either roads or walkways)

and undisturbed areas on the piedmont surface. Channels in the

undisturbed regions are wider (by nearly a meter) and deeper (by just over

centimeter) than the channels in the disturbed areas. Disturbed areas are

also more likely to contain channel heads. Roads and walkways also affect

the orientation of channels (channels tend to prefer flowing along a road

or walkway almost as much as flowing directly down-gradient).

This paper should be accepted for publication in "Environmental

and Engineering Geology Impacts on Military Operations," after the author

addresses some minor issues (discussed in detail below), and the more

major issue of the redundancy of the "Process Model," section of the

Discussion. The author makes it very clear exactly what data were taken,

how those data were treated, and does not try to overstep its own bounds

in coming to any speculative conclusions. My only really major problem

with this paper is the seemingly-inefficient manner in which the author

presents results and then repeats many of those results in the discussion.

A final minor problem I had with this paper is that none of the desert

process references are younger than 10 years old--I do not pretend to have

any idea about what the desert geomorphology literature is like, but it

would seem that someone would have been working on similar topics within

the last 10 years.