online_rational_composite:   Peak discharge for a composite catchment using the rational method INPUT DATA:     [Description]     [Example] Select:    SI units (metric) U.S. Customary units Drainage area Aa :    Warning: Undefined variable $areaunits in /var/www/html/ponce/onlinerationalcomposite.php on line 277 Runoff coefficient Ca :     Time of concentration tca :       min Drainage area Ab :     Warning: Undefined variable $areaunits in /var/www/html/ponce/onlinerationalcomposite.php on line 303 Runoff coefficient Cb :     Time of concentration tcb :       min Return period T :       yr OUTPUT: Qp  =  I  ∑ (C A) Peak discharge Qp :    Warning: Undefined variable $q in /var/www/html/ponce/onlinerationalcomposite.php on line 340 Deprecated: substr(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/html/ponce/onlinerationalcomposite.php on line 340   Warning: Undefined variable $dischargeunits in /var/www/html/ponce/onlinerationalcomposite.php on line 340 Design rainfall duration trd :    Warning: Undefined variable $trdesign in /var/www/html/ponce/onlinerationalcomposite.php on line 341 Deprecated: substr(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/html/ponce/onlinerationalcomposite.php on line 341   Warning: Undefined variable $timeunits in /var/www/html/ponce/onlinerationalcomposite.php on line 341 IDF Formula:        k T n I  =  _______________        (tr  +  b)m Coefficient k :   [Leave blank to set default k = 1000] Exponent n :   [Leave blank to set default n = 0.2] Coefficient b :   [Leave blank to set default b = 20] Exponent m :   [Leave blank to set default m = 0.7]   Your request was processed at  10:47:18 pm on April 3rd, 2025   [ 250403  22:47:18 ]    [140403]