Seth Kadish
Flow discharge and sediment transport models for estimating a minimum timescale of
hydrological activity and channel and delta formation on Mars
M. G. Kleinhans
“There is an illustrative legend of a conversation between Albert Einstein and his son Hans
Albert Einstein, wherein the son starts studying sediment transport, upon which the farther
remarks that he prefers the more simple problem of general relativity because it has fewer
variables.”
The bottom line: The goal of this paper is to use terrestrial water flow and sediment transport
models to further our understanding of martian fluvial geomorphology. In particular, Kleinhans
aims to provide a quantitative analysis of the formation of channel and delta formation on Mars.
The paper is heavily invested in the theory behind flow conditions and how sediment is moved
within the flow. Kleinhans spends more time discussing what we do not know than what we do,
but does provide estimates on the timescales of channel formation and spends some time
discussing specific cases of martian channels.
For basic equations, see papers by Komar, (1979, 1980).
Why is understanding flow and sediment transport on Mars such a complicated problem?
Conditions that we have measured on Earth are largely unknown for Mars (see paragraph 5!)
Specifically, the following questions are unresolved (to name a few):
 Were the flows under equilibrium conditions?
 What was the width of the channel at the time of the flow? Are we concerned with
bankfull flow?
 What is the Manning coefficient for Mars?
 How do we calculate friction (hydraulic roughness) and shear stress within the channels?
 What is the grain size distribution of the sediment? (Table 1)
 How is the sediment transported (bed load vs suspended load), and how concentrated is
the sediment within the flow?
 How can we use channel and delta morphology to constrain flow and sediment
conditions? (This one is somewhat resolved…)
Despite these unknowns, Kleinhans makes a number of key predictions:
 The grain-size distribution of sediment in flows is bimodal. It contains equal parts of
coarse gravel/cobbles and silt/sand.
 The formation of Gilbert-type deltas (GD) requires multiple aquifer reloadings. GD are
common at the end of smaller channels fed by sapping, and suggest bed load dominated
conditions and small transport rates.
 Hyperconcentration conditions likely played an important role in developing large
outflow channels and forming smooth deposits on the floor of an ancient ocean.
 Transport rate uncertainty is currently about one order of magnitude.
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Transport rates are smaller than calculated when 40% of the flow volume is sediment,
based on the sediment transport predictor of Ribberink (1998).
Formation timescales are very short for the channels and delta deposits (1 kyr to 1 Myr).
Channels were formed in multiples events because deltas take longer to build than the
minimal timescale of hydrological activity. However, the timescale of aquifer reloading
is very uncertain.