General Category => Using SLAMM => Topic started by: zhiliehui1 on November 14, 2019, 01:40:26 AM

Title: why the results with and without the dikes is no differet
Post by: zhiliehui1 on November 14, 2019, 01:40:26 AM
I am a student from China. I had several problems using slamm:
1\ I want to simulate the influence of the presence and absence of dikes on the coastal wetlands in the current and future situations. The data type of the dikes I used is the type of position and height. In the execution window, I made the Settings including and excluding dikes respectively, as shown in the screenshot below.However, the result is consistent with the fact that there is no dike, but obviously this is not consistent with the actual situation, please help me how to solve this problem.

2\In the process of model simulation, I noticed there are run model for NWI photo date (0) in execution window , refer to the technical manuals, but I still don't quite understand, why no matter whether the check this option, the result is 0 year which is not  consistent with the   starting year wetland distribution  in simulation , please help me to solve, whether in the simulation of actual need to check this option.
thanks a lot for your help sincerely
Title: Re: why the results with and without the dikes is no differet
Post by: Jonathan S. Clough on November 15, 2019, 01:36:25 PM
With regards to Question 1:

Thank you for your question, I'm not sure this is adequately addressed in the technical documentation.

The way that the "include dikes" and "dike location raster" works is that the model uses the connectivity algorithm to see if there is a connection between the land behind the dike and a "salt water source."  Specifically, the categories "riverine tidal," "estuarine water," "tidal creek," and "open ocean." must not appear behind the dike.  Otherwise the dike location raster will not work and the results will be no different.

You may check the connectivity of your site using the connectivity map option when setting up your model.

With regards to Question 2:

The time-zero run is a very important step.  To the extent possible, it should not be any different than the model's initial conditions.  It tests that the conceptual model, the wetland coverage, the elevation data, and the tide range data are all consistent.  In the results the initial condition is shown as "0" and the "time zero" result is shown as the first date of the simulation.

From the tech doc:
SLAMM can also simulate a "time zero" step, in which the conceptual model can be validated against the data inputs for your site. The time-zero model predicts the changes in the landscape given specified model tide ranges, elevation data, and land-cover data. Any discrepancy in time-zero results can provide a partial sense of the uncertainty of the model. There will almost always be some minor changes predicted at time zero due to horizontal off-sets between the land-cover and elevation data-sets, general data uncertainty, or other local conditions that make a portion of your site not conform perfectly to the conceptual model. However, large discrepancies could reflect an error in model parameterization with regards to tide ranges or dike locations, for example, and should be closely investigated.
Title: Re: why the results with and without the dikes is no differet
Post by: zhiliehui1 on December 03, 2019, 06:59:14 PM
Thank you for your detailed explanation. My problem has been solved. Thank you again.