Yoshiki SATO (GSJ, AIST)

Simple Delta Simulator ver1.00

This program allows you to estimate how the position of the delta front will change in response to sea-level change. HOWEVER, please note that this is based on a simple calculation based on the following assumptions and is not academically exactly. Note that this program is run by Javascript.

From "the Condition Settings", set the measurement time, initial delta shape (delta front position, angles of delta plain and slope), sea level fluctuation, and sediment supply. After the setteing, click the "Run" button to start the simulation, and the position of the delta (black colored circles and line) and trace of delta front (red colored line) will be described on "the Output Form" every second until reaching the measurement time. You can check the status of the initial settings in a graph by click the "Confirm" button on the right side of the condition setting form.

CAUTION

Do NOT strike the Run button repeatedly. Duplicate processing will occur and the calculation will not be performed correctly.
Calculation will stop when the delta front position becomes negative.
The angle of delta plain should be smaller than that of delta slope.
If you run a series of calculations, the process may become slow. Please reload as necessary.
If you find any strange behavior, please let me know.

Assumptions

River (Delta) immediately reach an equilibrium (graded) state in response to sea level change.
The angles of delta pline slope are constant, not change in response to sea level change.
For simplifying calculation, we assume that the angle of prodelta is 0 degree.
A certain percentage (ρ) of the amount of sediment eroded when the delta reaches equilibrium contributes to the formation of a new delta.
Sedimentation and erosion by forces other than rivers, such as waves and tides, are NOT considered.


Condition Settings
Setting examples

Measurement time		[s]	Cross-sectional view of initial delta

Initial delta shape
Position (X0)
Position (Y0)
Angle of delta plain		Constant: [degree]
		Inverse phase of SL: (amplitude) [degree] *Under construction
Angle of delta slope		Constant: [degree]

Sea level fluctuation (Sum of Factors 1 - 5)			Change in sea level & sediment supply
Factor 1	Initial value（=Y0）
Factor 2	Linear (=tectonic)	* time (Uplifting + ; subsidence -)
Factor 3	Sine curve	sin(2 phi/ ( *time－ )
Factor 4	Linear (asymmetry)	Amplitude: Rising period:[s] Falling period:[s]
Factor 5	Fourier	Amplitude: n: Periodicity:

Sediment supply
Sediment supply rate (sum of Factors 1 & 2)		Factor 1 (constant):
		Factor 2 (synchronous with sea level): * (Amplitude)
Lost ratio of eroded sediments (ρ)


Output Form
Current Status		Cross section of the delta
Time [s]
Sea level
X
Y
Area
Change in sea level & sediment supply