Drainage Specific Parameters

The following specific parameters are shown for drainage networks. They are shown in Table parameters along with the general parameters of the spreadsheet.

Layer hatch
Layer to set for basin hatches. Each network may have a different layer and is easier to define this layer the worksheet that the

CAREA command.

Calculation of TE
Calculation of concentration time at the entrance of the structure.
This parameter serves to inform which equation to use to calculate the time TE, or runoff (inlet time).

In the Basic Manual of hydrology, DNIT (IPR 715), are defined as:

Basin	Area
Small	< 2.5 km²
Medium to Large	> 4.6 to 3476 km²

The equations implemented are:

Arbitrated - If selected, the column TE is available for editing
Kerby - Applicable to small basins TE = (37 * (0.5 * LT / DeclTal) ^ 0.47)
Kirpch - Originally applicable to watersheds smaller than 0.8 km ². According DNIT is applicable to small, medium and large bowls. TE = (57 * (LT ^ 3/H) ^ 0.385)
Picking - Applicable to small basins TE = (5.3 * (LT ^ 2 / DeclTal) ^ (1.0 / 3.0))
USCE (U. S. Corps of Engineers) Applicable to small basins TE = (18 * (LT / DeclTal ^ 0.25) ^ 0.76)
Ven Te Chow - Applicable to small basins TE = (25.2 * (LT/ DeclTal ^ 0.5) ^ 0.64)

DNOS - Applicable to any basin TE = ((10/vk) * AreaContr ^ 0.3 * LT ^ 0.2/(DeclTal ^ 0.4))
AreaContr - contribution area in hectares
With the values of vk:

Land	vk
Land sandy clay, covered with dense vegetation, high absorption	2.0
common ground, overgrown, appreciable absorption	3.0
Land clay, covered with vegetation, average absorption	4.0
Land soils, vegetation average, poor absorption	4.5
Land with rock, sparse vegetation, low absorption	5.0
Rocky terrain, sparse vegetation, reduced absorption	5.5

Kirpch Modified - Applicable to any basin TE = (85.2 * (LT^3/H) ^ 0.385)
George Ribeiro - Applicable to any basin TE = (16 * LT/((1.05 - 0.2 * pr) * (100 * DECTAL) ^ 0.04))
Where:
pr - is the portion of the basin covered by vegetation (0 % to 100 %)
Passini - Applicable to any basin TE = (6.42 * (AreaContr * LT) ^ (1.0/3.0) / DECTAL ^ 0.5)
AreaContr - basin area in square kilometers
Ventura - Applicable to any basin TE = (7.62 * (AreaContr / DECTAL) ^ 0.5)
AreaContr - basin area in square kilometers
Rossi - Contra indicated in any basin TE = (46.2 * (LT/DECTAL ^ 0.5) ^ 0.295)
Giandotti - Applicable for medium and large bowls TE = 60 * ((4 * AreaContr ^ 0.5 + 1.5 * LT)/(0.8 * H ^ 0.5))
AreaContr - basin area in square kilometers
Lag TE = Kn * (0.0053 * LT * Lc)/DECTAL ^ 5) ^ 0.38
KN - is the average of the Manning coefficients of the watercourses most important basin (ranging from 0.01 to 0.3)
JohnCollins TE = (44 * (LT/dm) * (AreaContr ^ 2 /DECTAL) ^ 0.2)

dm = (4 * AreaContr/PI) ^ 0.5
AreaContr - basin area in square kilometers
PI - mathematical constant pi
CN TE = (108 * 1.3 * LT ^ (1000/CN - 9) ^ 0.7/H ^ 0.5)

In all equations:
TE, will be given in minutes
LT, length of thalweg, will be given in kilometers
H, the thalweg elevation, will be given in meters
DECTAL, average slope of the thalweg is given in (m/m) or dimensionless.

Tr
Recurrence Time.
It's time to recurrence of rain, or the time it takes to repeat a rain of equal intensity and duration. According to Cetesb (São Paulo, Brazil) ranges from 2 to 10 years:

Location	Years
Residential	2
Commercial	5
Areas with public buildings, airports	2-5
Areas highly valued	5-10

In general municipalities impose this value. Always search for the mayor of the municipality where the work will be executed if they recommend these parameters.

DNIT recommends 15 years for works to existing and 25 new.

Constant TR
There are situations where we need to design the principal collectors with TR value greater than that of the secondary branches. Use this parameter to enable editing of the TR column in the spreadsheet drainage.

Rain Equation
To calculate drainage networks, it is necessary to define some parameters. The basic equation of rain to be used.
In the spreadsheet, you will find at the bottom left, the parameters frame where to change these parameters:

Clicking the item "Equation", click the button with three dots and opens a table with all the available equations:

Just select the corresponding row. You can also edit the equation in the selection screen and delete, or add equations.

When editing equations, Take care to write them correctly, so it can be evaluated.

equation must always be a function of recurrence time (Tr) in years and Concentration Time (tc) in minutes. The answer (I) should be given in mm/h .

Important:
To get the natural logarithm of a number, use log (n) and to get the logarithm base 10, use log10 (n).

A good tip is to use the program pluvio 2.1, is a specific software for equations of rain throughout Brazil. Download pluvio.

Another source for finding the equations of rain is the page: http://tbn2net.appspot.com/procuraEQ

Calculation method
According to some authors, formulas based on rational method exhibit a hysteresis (CR) lower than 1. It is as if the rational method super size flow in large areas of contribution. The C3DRENESG implements three ways to calculate this coefficient:

Original Method
This method is implemented since the first version of C3DRENESG. The equation that returns CR is:

cr = A ^ (- 1/n)

Where:

A, is the watershed area in hectares,
n, is a function of the slope of the basin:

Slope n Author

<5/1000 4 Bürkli - Ziegler

<1/100 5 Mc Math

> 1/100 6 Brix
Method Brasilia
This method is used by the offices of Brasilia - DF (Brazil) and the equation that returns CR is:

cr = A ^ (- k)
Where:

A, is the area in hectares of the basin

values of k:

Area (ha) k

0 - 10 0.0

10 - 50 0.05

50 - 150 0.1

> 150 0.15

If necessary, you can edit this table by clicking the item "delay coefficient"
Method DNIT
For sizing made using the method of DNIT, check manual drain of the same
The equation that returns CR is:
cr = A ^ (- 0.15)

Where:

A, is the area of basin
Note: that the equation is only valid for A greater than 1 hectare. For smaller values than 1 hectare, take CR = 1

Slope	n	Author
<5/1000	4	Bürkli - Ziegler
<1/100	5	Mc Math
> 1/100	6	Brix

Area (ha)	k
0 - 10	0.0
10 - 50	0.05
50 - 150	0.1
> 150	0.15

All these values can be saved to the C3DRENESG.ini file, to be reused in other projects. To do this click the right mouse button on the box parameters and click: