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Does the model simulate sediment inputs as a function of the tydal range?

Started by Pat Prado, April 04, 2018, 06:42:19 AM

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Pat Prado


I was wondering if someone could clarify if SLAMM takes into account that higher sediment inputs seem to happen in systems with greater tydal ranges, which could lead to enhanced resilience to SLR compared to systems with lower tydal ranges. Is the model calibrated to simulate this effect?

Many thanks in advance!!

Jonathan S. Clough

Tidal ranges affect SLAMM in many ways.  Certainly the model predicts significantly enhanced resilience to SLR for larger tidal range sites.

For one thing, a fixed change in tide levels (due to SLR) is a much higher percentage of the tide range in a microtidal site than a macrotidal.  This means that a marsh (that exists within the "tidal frame") can have much more elevation capital in a macrotidal site.

But with regard to the question at hand.  The SLAMM model does not directly model sediment inputs but those inputs come into account in the relationship between marsh accretion rate and marsh elevation.   See for example Figure 4 in this document.  This figure was derived based on the calibration of a model that does explicitly model sediment inputs (MAM3) 

We recognized that a model such as MAM3 generally predicts a single parabolic accretion-rate response to SLR (if you hold sediment inputs and tide range constant over time).  (The parabola has accretion rates on the y axis and marsh elevation relative to MTL on the x axis)  Therefore we allow for an input of this type of parabola to SLAMM.  A site with a larger tide range has more elevation capital to work with and will generally accumulate more sediment over a period of SLR.  MAM3 also predicts increased sedimentation rates in sites with larger tide ranges.

To generate the required parabola a site-specific empirical data analysis or application of a site-specific mechanistic model should be utilized. 

Hope this is useful and sorry about the long delay in response