Drainage Calculators

Calculate optimal area drain spacing based on surface slope, ponding constraints, and drain capacity. Uses sheet flow analysis from TR-55 and HEC-22 methods. Professional drainage design tool for civil engineers.

Calculate optimal channel dimensions for maximum hydraulic efficiency. Design channels with minimum excavation for a given discharge using rectangular, trapezoidal, or triangular sections.

Design bioretention facilities with underdrain systems for sites with poor native soil infiltration. Calculate required area, storage volumes, underdrain capacity, and infiltration split using ASCE and Virginia DEQ methodology.

Calculate catch basin sizing, outlet pipe capacity, and sediment storage volume. Design storm drainage inlets using Manning's equation. Free professional-grade hydraulics calculator.

Design channel linings using permissible velocity or tractive force methods. Evaluate grass, riprap, concrete, and other lining adequacy for erosion protection.

Calculate head losses in channel transitions including contractions and expansions. Supports abrupt, gradual, warped, and wedge geometries with standard loss coefficients.

Calculate cistern sizing for rainwater harvesting. Determines collection potential, storage requirements, and annual water balance using ASABE S597.1 and ARCSA guidelines.

Calculate flow in compound channels with multiple subsections using the divided channel method. Analyze main channel with floodplains, composite roughness, and velocity distribution.

Calculate critical depth for open channels and pipes. Determine the depth at which specific energy is minimum and Froude number equals 1. Supports circular, rectangular, trapezoidal, and triangular sections.

Calculate outlet control hydraulics for culverts including headwater depth, outlet velocity, critical depth, normal depth, and head loss breakdown. Uses FHWA HDS-5 methodology for circular and box culverts.

Calculate required downspout size based on roof area and rainfall intensity. Uses IPC tables for round and rectangular downspout sizing. Free professional-grade drainage calculator.

Calculate dry well sizing for stormwater infiltration. Determines storage volume, infiltration capacity, and drawdown time using ASCE MOP 77 methodology.

Design stilling basins, impact basins, and energy dissipation structures using FHWA HEC-14 and USBR methodology. Calculate basin dimensions, sequent depth, and energy dissipation.

Perform flood frequency analysis using Log-Pearson Type III and Gumbel distributions per USGS Bulletin 17C. Estimate flood magnitudes for various return periods from annual peak flow data. Professional-grade statistical hydrology tool.

Calculate foundation drain sizing for basement and crawlspace waterproofing. Determines pipe capacity, groundwater inflow, and sump pump requirements using HEC-22 methodology.

Calculate French drain capacity, pipe sizing, and storage volume. Design subsurface drainage systems using Darcy's Law and Manning's equation. Free professional-grade drainage calculator.

Calculate Froude number and classify flow regime for open channels. Determine if flow is subcritical, critical, or supercritical. Includes wave celerity and specific energy calculations.

Calculate water surface profiles using the Direct Step Method. Analyze backwater and drawdown curves with automatic profile classification (M1, M2, S1, etc.) for open channels.

Calculate green roof stormwater retention and detention performance. Determine water holding capacity, runoff reduction, peak flow delay, and structural loads using FLL guidelines and ASCE methodology.

Calculate gutter flow capacity using Manning's equation. Analyze K-style, half-round, and box gutters. Determine flow velocity, hydraulic radius, and Froude number. Free professional-grade roof drainage calculator.

Calculate runoff hydrographs using unit hydrograph convolution. Applies the principle of superposition to combine rainfall increments with unit hydrograph response per NRCS NEH Part 630.

Design infiltration trenches for stormwater management. Calculate required trench dimensions, storage volume, infiltration capacity, and drawdown time using EPA and ASCE methodology.

Calculate inlet interception efficiency for roadway drainage using HEC-22 methodology. Analyze grate, curb-opening, and combination inlets. Determine captured and bypass flows. Free professional-grade drainage calculator.

Route inflow hydrographs through detention basins and reservoirs using the Modified Puls (Storage-Indication) method. Calculate peak attenuation, lag time, and maximum storage for detention pond design.

Calculate open channel flow using Manning's equation. Supports rectangular, trapezoidal, triangular, and parabolic channel shapes. Free professional-grade hydraulic engineering calculator.

Calculate pipe flow discharge, velocity, and hydraulic properties using Manning's equation. Supports full and partial flow in circular pipes with imperial and metric units. Free online tool for drainage engineers.

Calculate preliminary detention storage requirements using the Modified Rational Method. Analyze multiple storm durations to find critical duration and maximum required storage. Professional hydrology tool.

Route flood hydrographs through channel reaches using the Muskingum method. Calculate peak attenuation, translation time, and outflow hydrograph for rivers and streams. Professional hydrology tool for civil engineers.

Calculate normal depth for open channels and pipes using Manning's equation. Iteratively solve for the depth at which uniform flow occurs. Supports circular, rectangular, trapezoidal, and triangular sections.

Design riprap aprons and outlet protection structures for culverts using FHWA HEC-14 methodology. Calculate D50 stone size, blanket thickness, and apron dimensions.

Calculate outlet velocities from pipes and culverts to assess erosion potential. Determine scour depth, scour hole dimensions, and protection requirements using FHWA HEC-14 methodology.

Calculate permeable pavement system design including base course depth, storage volume, and infiltration capacity using ASCE and EPA methodology.

Calculate preliminary detention pond storage requirements using the Modified Rational Method. Size orifice and weir outlets for stormwater management facilities. Professional-grade hydrology tool for civil engineers.

Calculate rain garden sizing for stormwater management. Determines required area, storage volumes, and infiltration capacity using ASCE and EPA methodology.

Generate SCS/NRCS 24-hour rainfall distributions (Type I, IA, II, III) for design storms. Creates hyetographs showing rainfall intensity over time per TR-55 methodology.

Calculate peak stormwater discharge using the Rational Method (Q = CiA). Free online calculator for drainage engineers and civil engineering professionals.

Calculate riprap stone sizing using Isbash, USACE, HEC-11, or Maynord methods. Determine D50 median stone size, gradation requirements, and blanket thickness for channel protection.

Calculate roof drain size for flat and low-slope roofs. Uses IPC tables for primary drains, overflow drains, and scuppers. Free professional-grade drainage calculator.

Look up runoff coefficients (C values) for the Rational Method or calculate composite coefficients for mixed land use drainage areas. Free online tool for drainage engineers.

Calculate stormwater runoff depth using the SCS (NRCS) Curve Number method. Includes runoff calculation, composite CN for multiple areas, and CN lookup tables. Free online calculator for drainage engineers.

Generate SCS triangular unit hydrographs for simplified runoff analysis. Calculates peak discharge, time to peak, and runoff volume per TR-55 methodology.

Calculate peak discharge and generate storm hydrographs using the SCS/NRCS dimensionless unit hydrograph method. Professional-grade hydrology tool for medium-scale watershed analysis.

Calculate required detention storage volume using the Modified Rational Method, Baker Method, FAA Method, and simplified approaches. Professional stormwater management tool for civil engineers.

Calculate sump pump capacity and pit sizing for basement drainage. Determines required pump capacity, total dynamic head, cycle frequency, and verifies motor protection requirements.

Calculate tailwater depth at culvert outlets with support for multiple channel types (rectangular, trapezoidal, triangular, natural). Analyze normal depth, critical depth, Froude number, flow regime, and outlet submergence. Optional rating curve generation.

Calculate time of concentration (Tc) using multiple methods including Kirpich, FAA, NRCS Lag, Kerby-Hathaway, and TR-55 segmental approach. Essential for hydrologic analysis and drainage design.

Calculate trench drain capacity using Manning's equation. Determines flow capacity, velocity, and grate interception efficiency for linear drainage systems.

Design underground detention systems for stormwater management. Calculates storage volume, outlet sizing, and drawdown time per ASCE MOP 77 and FHWA HEC-22 methodology.

Calculate peak flood flows at ungauged sites using USGS regional regression equations. Estimate peak discharges for various return periods based on drainage area and basin characteristics. Professional-grade screening tool for civil engineers and hydrologists.

Calculate vegetated swale hydraulics including normal depth, velocity, and capacity using Manning's equation with variable roughness based on vegetation retardance.