The Landlab v1.0 OverlandFlow component: a Python tool for computing shallow-water flow across watersheds

Adams, Jordan M.; Gasparini, Nicole M.; Hobley, Daniel E. J.; Tucker, Gregory E.; Hutton, Eric W. H.; Nudurupati, Sai S.; Istanbulluoglu, Erkan

doi:https://doi.org/10.5194/gmd-10-1645-2017

Articles | Volume 10, issue 4

https://doi.org/10.5194/gmd-10-1645-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/gmd-10-1645-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 10, issue 4

Model description paper

|

20 Apr 2017

Model description paper |

| 20 Apr 2017

The Landlab v1.0 OverlandFlow component: a Python tool for computing shallow-water flow across watersheds

Jordan M. Adams, Nicole M. Gasparini, Daniel E. J. Hobley, Gregory E. Tucker, Eric W. H. Hutton, Sai S. Nudurupati, and Erkan Istanbulluoglu

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Final revised paper (published on 20 Apr 2017)
Supplement to the final revised paper
Preprint (discussion started on 08 Nov 2016)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

SC1: 'Exective Editor Comment on "The Landlab OverlandFlow component: a Python library for computing shallow-water flow across watersheds"', Astrid Kerkweg, 30 Nov 2016
- AC1: 'Response to Astrid Kerkweg', J.M. Adams, 05 Feb 2017
RC1: 'please see comments below and attached', Dapeng Yu, 20 Dec 2016
- AC2: 'Response to Dapeng Yu', J.M. Adams, 05 Feb 2017
RC2: 'Review of Landlab OverlandFlow component - Adams et al', Katerina Michaelides, 06 Jan 2017
- AC3: 'Response to Katerina Michaelides', J.M. Adams, 05 Feb 2017

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by J.M. Adams on behalf of the Authors (05 Feb 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (06 Feb 2017) by Jeffrey Neal

RR by Dapeng Yu (15 Feb 2017)

RR by Katerina Michaelides (19 Feb 2017)

Suggestions for revision or reasons for rejection

1. Fundamentally, the paper needs to clarify a couple of crucial things that at the moment are still causing some confusion:

a) The term “hydrologic” implies hydrological processes (e.g. rainfall-runoff generation via infiltration and subsurface-surface water linkages); whereas the term “hydraulic” is used to denote the characteristics of movement of water through a system. As is, this paper describes the hydraulic processes (not the hydrologic processes) and it needs clarification. This confusion is apparent in the conflation of flood inundation models with rainfall-runoff models (e.g. LISFLOOD-FP is not a rainfall-runoff model – it is a flood hydraulic model which routes a hydrograph through a channel-floodplain system but does not generate that hydrograph from rainfall nor does it simulate overland flow on un-channelized hillslopes). Therefore, I think the authors need to use the correct terminology when referring to hydraulic vs hydrological processes in the context of this new model component and to decide whether this is a hydrologic model or a hydraulic model (which is what I think it is).

b) Having read both versions of the paper several times now, I’m still confused as to whether this model routes flow over the hillslopes and channels or only in channelized components. In this revised version, I think I’m even more confused because on page 16 [13-14] it is stated that the model makes no distinction between hillslopes and channels which would lead one to believe that the model routes water over the entire grid (hillslopes and channel) but from the results in Figure 8 c&d it appears as though the ‘overland flow’ routing is only applied in the channelized parts (i.e. water depths and shear stresses on non-channelized components are zero). The term ‘overland flow’ implies hillslopes (as opposed to channel flow). So can the authors please clarify these aspects as they are quite important? If it is only a channel flow model, then perhaps they may consider revising the name (as it is misleading) and the part of the title that says “across watershed”?! If flow routing does take place on the non-channelized parts of the basin (i.e. the hillslopes) then can I please request this is made clear upfront?
If from 1) and 2) the authors ascertain that the model is a channel flow hydraulic model (as opposed to basin-scale hydrologic model), then this needs to be clear upfront as the two mean quite different things.

2. The abstract seems overly long and detailed and still contains some confusing statements. I think it would benefit from becoming more succinct and direct. For example, consider rewording the opening sentences from:

“Hydrologic models and modeling components are used in a wide range of applications. Geomorphologists include aspects of hydrologic models, albeit in a highly simplified manner, when using long-term landscape evolution models to approximate how flowing water shapes landscapes over thousands to millions of years. Most landscape evolution models make assumptions that reduce overland flow into a function of drainage area and precipitation rate, removing physical parameters like water surface slope 5 and surface roughness from flow calculations in favor of computational speed.”

To something like:

Representation of water flows in long-term landscape evolution models (LEMs) is simplistic compared to short-term hydrological models due to assumptions taken to reduce complexity and increase the computational speed necessary to run simulations over thousands to millions of years.

3. There is still confusion about the timescales of applicability of this model. On p1 [13] of the Abstract it is stated that the paper will illustrate the application of the new component on event-based and decadal timescales. The final sentence of the Abstract (p2, 2) states that the model takes a few hours to run simulations up to 10,000 years. So given that Landlab functions predominantly as an LEM, and given the speed of running 10,000 years, why didn’t the authors demonstrate some long term results in this paper? I think that would be a great addition.
4. P2 [22] Remove “moving downstream”
5. P3 [1] Abbreviate landscape evolution models to LEMs throughout the paper
6. P3 [6] Flood inundation models like LISFLOOD are not to be confused with rainfall-runoff models (see point 1a above). This section needs reworking.
7. P4 [13] Why are you limiting your simulations to 10 years and not showing off the 10,000 year capability? (see point 3 above)
8. P13 [section 7] Does ‘long-term fluvial erosion’ here mean decadal? I would reword as the expectation from someone reading this heading is that you are going to be simulating hundreds to thousands of years at least.
9. P14 [15] Does ‘short-term landscape evolution’ here mean decadal? Or event-based? In any case, short-term landscape evolution is not usually used to denote either event-based on decadal scale landscape changes.
10. P15 [10] I remember highlighting this point in my review of the original manuscript. What is the geomorphic meaning of comparing 10 years of incision depth with long-term steady state incision? Aren’t you comparing apples and oranges here?
11. P16 [12-14] Sentence is unclear. Clarify whether it is the manuscript or the model that make no distinction between hillslope and channel processes. And see point 1b above.

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ED: Publish subject to minor revisions (Editor review) (20 Feb 2017) by Jeffrey Neal

AR by J.M. Adams on behalf of the Authors (02 Mar 2017) Author's response Manuscript

ED: Publish as is (16 Mar 2017) by Jeffrey Neal

Short summary

OverlandFlow is a 2-dimensional hydrology component contained within the Landlab modeling framework. It can be applied in both hydrology and geomorphology applications across real and synthetic landscape grids, for both short- and long-term events. This paper finds that this non-steady hydrology regime produces different landscape characteristics when compared to more traditional steady-state hydrology and geomorphology models, suggesting that hydrology regime can impact resulting morphologies.