How hydrologic and hydraulic calculations are worked out.

First, the potential maximum soil moisture retention *(S)* is computed with the
user-defined curve number *(CN)* and used to calculate the initial abstraction *(Ia)*.

With the user-define total storm depth *(P)*, computed maximum soil moisture
retention, and initial abstraction, the resulting runoff depth is computed.

Runoff Depth =
*(P-Ia)*^{2}
*(P-Ia+S)*

With each runoff burst depth occurring at each time step, a small "burst" hydrograph
is computed based on the dimensionless SCS (Soil Conservation Service) Unit Hydrograph. This
dimensionless unit hydrograph was derived based on many hydrographs of varying size
and geographic location and is made dimensionless by normalizing the flow with the peak flow
*(q/q _{peak})* and by normalizing the time with the time of peak

In order to populate each burst hydrograph, the time to peak *(t _{peak})* and peak flow

where *t _{c}* is the user-defined time of concentration (hours),

With the calculated t_{peak} and q_{peak}, the flow at each time step is solved for
based on the shape of the Dimesionless SCS Unit Hydrograph shown in Figure 1 resulting in a burst hydrograph
for the particular runoff depth.

Each burst hydrograph is then added together to form the runoff hydrograph for the overall storm.

Discharge and overflow from a basin resulting from inflow runoff *(q _{inflow})* is governed
by a general continuity equation as follows:

where *storage* is dependent on the user-defined basin geometry parameters (area, void space, height) and
*seepage* represents the volume of water lost to infiltration.

Outlflow from the basin *(q _{outflow})* is can be broken down into orifice flow and weir flow
as follows:

Orifice flow is governed by the orifice equation which is essentially a rearrangment of the Bernoulli Equation

where *C* is a coefficient (assumed to be 0.62), *A* is the cross-sectional area of the orifice based on the
user-defined orifice diameter, *g* is the force of gravity, and *h* is the head on the orifice at a given point in time.

Similarly, weir flow is calculated as follows:

where C_{d} is the weir discharge coefficient, *b* is the width of the weir, *g* is the force of gravity, and *h*
is the head on the weir at a given point in time.

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