View source for Doi.org/10.1006/ecss.1996.0091

== Target Article ==
<div style="text-align:justify">
Ridd, P.V. (1996). Flow through animal burrows in mangrove creeks. Estuarine Coastal and Shelf Science. 43(5), 617-625
Available at: http://www.sciencedirect.com/science/article/pii/S0272771496900918
DOI: https://doi.org/10.1006/ecss.1996.0091
</div>

== Significant Claim ==
<div style="text-align:justify">
This paper looks at the flow through mangrove crab burrows with multiple openings caused by water flowing over the surface of the burrow. The surface water flowing into or out of a mangrove swamp must have a small surface slope to drive the water against the opposing friction forces caused by the shallow and hydrodynamically rough surface of the swamps. Wolanski et al (1992)<ref name="REF01">Wolanski, E., Mazda, Y. & Ridd, P. V. 1992. Mangrove Hydrodynamics. In Tropical Mangrove Ecosystems (Robertson, A. & Alongi, D., eds). A.G.U., Washington, pp. 43–61.</ref> estimate that the manning friction coefficient inside a mangrove swamp is around ten times higher for a mangrove swamp than for a similar area without vegetation. The water slope thus creates a different water level, and thus pressures, over different openings within the burrow thus potentially driving a current through the burrow. 
</div>

== Possible caveat with this article ==
<div style="text-align:justify">
The section on “Theoretical predictions of burrow flow” is under contention. The flow rate inside the burrow is not only dependent upon the pressure gradient but also the friction coefficients and length of the burrow. This paper gives a simple method to determine the friction coefficients for the burrow, and also the length of the burrow by setting up an oscillation in the water level in the burrow when it is not covered by water. The burrow is modelling as a classical simple harmonic oscillator and the period of oscillation of the water level fluctuations, and the time constant for the decay of the oscillations, is used to determine the friction coefficient and burrow length. To first order the rate of decay of the oscillations is dependent upon the friction coefficients, and the period of the oscillations is also depending upon the burrow length. 

There are two reservations about this method which have become evident as more work has been done in the field. The first problem relates to modelling the burrow as a simple “U” tube. This would seem to be an unreasonable model unless it can be demonstrated that the burrow has only two openings. However, Stieglitz et al (2000)<ref name="REF02">* [https://link.springer.com/article/10.1023/A:1003925502665] T.C. Stieglitz, P.V. Ridd, P. Müller  2000. Passive irrigation and functional morphology of crustacean burrows in a tropical mangrove swamp. Hydrobiologia, 421, pp. 69-76, doi:10.1023/A:1003925502665</ref> has shown that burrows are likely to have a far more complicated morphology with multiple openings, and complicated interconnected galleries, and loops. Thus the method would have limited value in determining length. Ridd (1996) used the burrow length to calculate flow speeds within the burrow (eq 10) so the calculated flow speeds must be considered to be questionable.

The second issue relates to the assumption that the flow in the burrow is controlled by a simple balance between the pressure gradient (caused by the surface slope) and the opposing friction force. It has been demonstrated (Heron and Ridd, 2003<ref name="REF03">* [https://doi.org/10.1016/S0272-7714(03)00068-4] S.F. Heron, P.V. Ridd 2003. The effect of water density variations on the tidal flushing of animal burrows. Estuarine, Coastal and Shelf Science, 58, pp. 137-145., doi: 10.1016/S0272-7714(03)00068-4</ref>, Hollins et al., 2009<ref name="REF04">* [https://doi.org/10.1016/j.ecss.2009.03.007] Hollins, S., S. F. Herron & P. V. Ridd, 2009. Methods for monitoring tidal flushing in large animal burrows in tropical mangrove swamps. Estuarine, Costal and Shelf Science 82: 615–620., doi: 10.1016/j.ecss.2009.03.007</ref>) that water in the burrow may have a considerably different salinity to the water entering the swamp and thus there is a density generated pressure gradient force when water is partially displaced from the burrow (Heron and Ridd 2003 <ref name="REF03" />). If the density of water in the burrow is sufficiently high, it is possible that a given surface slope will be unable to displace the all water in the burrow, i.e no flow will occur. Neglecting this density affects makes the use of the governing equation (eq 1) questionable.
</div>

== References ==
<div style="text-align:justify">
<references />
</div>

== Comments ==
In WL-Letters you have the freedom to respond to any caveat that may be inaccurate.
<br />-- [[User:Andutta|Andutta]] ([[User talk:Andutta|talk]]) 18:11, 6 July 2022 (UTC)