Project Settings

The Project Settings dialog configures calculation methodology, hydrology, design criteria, and display options for your project. Open it from the Settings button in the toolbar.

The dialog has six tabs. Hydrology answers "where does runoff come from"; each module tab (Storm Drain, Culverts, Inlets) owns its own storm events and its own parameters.

Tab	Contents
Project	Project identification and two per-user preferences.
Hydrology	Hydrology mode, the HydraLink link, rational-method options and defaults, and the IDF Curves sub-tab.
Storm Drain	Storm events for the pipe system, flow accumulation, every design parameter and compliance check, and the quantity-takeoff depth classes.
Culverts	Storm events for culvert-designated alignments.
Inlets	The inlet module on/off switch and its storm events.
Display	Per-quantity decimal places for grids, CAD tables, and Excel.

Label styles are not in this dialog; picking and applying them is one action on Output ▾ > Apply Label Styles…. See Profiles & Labels.

Project Tab

Basic project identification. These values appear on exported reports.

Setting	Description
Project Name	Name of the project
Job Number	Project or job number for tracking
Engineer	Engineer of record

Storm Drain Tab

Everything that governs the pipe system: which storms it is run for, how flow accumulates through it, the hydraulic calculation engine, design constraints, and pipe design criteria.

Storm Events

Storm return periods are configured as a small grid rather than a single design/check pair. Add as many storm events as your project needs and assign each one a role.

Column	Description
Storm	The return period label (e.g. "10-yr"), read-only once added.
Role	Design, Check, or Analysis. At most one Design and one Check.
Cf	Read-only. The storm frequency adjustment factor this storm will be computed with, resolved from its return period. Cf is a property of the return period rather than of the module analysing it, so it is set once in the Cf table on the Hydrology tab and shown here for traceability. See Frequency Adjustment (Cf).
Inlet	Checkbox. When checked, this storm's captured inlet flows feed into the storm drain HGL calculation for that storm.

This grid does not create storms — it assigns ones already declared on the Hydrology tab's Storm Events table. The combo box beneath the grid lists only project storms this module hasn't picked up yet; pick one and click + Add to assign it. The x on a row unassigns that storm from the storm drain (it stays on the project and on any other module still using it). When a Check role is assigned, a Sizing Storm radio (Design / Check) appears, controlling which storm Auto Design uses for pipe sizing.

Culverts and inlets have their own identical grids on their own tabs, so their storms and roles are independent: a municipality that sizes pipes for 10-year but checks inlet spread against 100-year declares both on the Storm Events list, then assigns the role it wants on each tab. Two things are shared rather than per-module: the return periods themselves, and C_f: every module resolves C_f from the Storm Events table by return period, so a 100-year culvert run uses the 100-year C_f whatever the storm drain is sized for.

Flow Accumulation

Three switches that sound alike but do different things. Each is only shown in the hydrology mode that actually uses it.

Setting	Default	Description
Include pipe travel time in Tc	Off	Rational modes only (Manual, or HydraLink on the Basin Parameters basis). Accumulates Tc downstream as max(upstream Tc + pipe travel time, local inlet time). Off means each node uses its own inlet time alone.
Travel velocity basis	Q / Afull	Radio buttons beneath the checkbox (active only when it's on): which velocity converts pipe length to travel time. Q / Afull — discharge over the full-barrel area, the legacy DFW spreadsheet convention (also matches the Excel export). Manning full-barrel normal velocity — from geometry and slope only, flow-independent, slightly conservative at partial flow.
Carry larger upstream Q downstream	Off	Rational modes only (same two), and it touches Q, never Tc. When on, a node's computed peak flow never drops below the total flow arriving in its incoming pipes (TxDOT-style "use the higher discharge"). Off accepts standard practice: Q = ΣCA·i(system Tc) may decrease downstream as Tc growth lowers intensity.
Accumulate Flows	On	Shown in Peak Flows Only mode and on the HydraLink Fixed Flows basis — the two cases where directly entered or imported flows drive the network. Whether those flows sum downstream through junctions. Off means each pipe uses only its upstream node's flow. The rational method always accumulates ΣCA, so this switch has no meaning in the rational modes.

Friction Method

Setting	Description
Friction Method	Manning's equation (default) or Hazen-Williams equation. Applies project-wide.
Default Manning's n	Default roughness coefficient for new pipes (default: 0.013). Can be overridden per pipe.
Default Hazen-Williams C	Default smoothness coefficient when Hazen-Williams is selected (default: 150).

Tailwater

Setting	Description
Default Tailwater Method	How to compute the downstream boundary condition at outfalls: Critical Depth Average — (Dc + D) / 2. Common conservative default. Crown — Tailwater at the pipe crown (invert + rise). Most conservative. Normal Depth — Manning's uniform flow depth at the outfall slope. Individual outfalls can override this with a manual tailwater elevation.

Design Constraints

Setting	Default	Description
Default Circular Family	First circular family in the parts list	Part family a pipe re-points to when its shape is switched to Circular. Without a pin here, the switch lands on the first circular family in the drawing's parts list, which can land on PVC in an RCP design.
Default Box Family	First box family in the parts list	Same as above, for a switch to Box.
HGL Method	Gradually Varied Flow	Which construction draws the HGL inside each barrel: Gradually Varied Flow (the rigorous engine), Simplified Normal Depth, or Simplified Normal Depth (Crown Reset) — the two hand-reproducible conventions a municipal reviewer checks against. Sizing and the results grid always read the same setting, so they can never disagree.
Min Slope Basis	Fixed Value	How the minimum slope floor is resolved, per pipe size: Fixed Value uses the Minimum Pipe Slope scalar for every size (legacy default); Velocity-Based derives each size's minimum from the slope that reaches Min Velocity flowing full (the self-cleaning basis municipal per-diameter tables are built from, letting large trunks run flatter than the scalar); Greater of Both keeps the scalar as an absolute floor under the velocity-based value. Auto Design and the compliance grid's Min Slope check both resolve through this setting, so they never disagree.
Min Diameter	Smallest catalog size	Smallest allowable pipe size for Auto Design. Chosen from a drop-down of the actual sizes in the selected part family, since a minimum that isn't a size you can buy would either exclude every candidate or none of them. A note under the field names the family the list came from. Change the family in the main window's side panel. For box sections the list is rises, matching how Auto Design filters them. If the drawing has no pipe parts list, the field falls back to plain numeric entry and says so.
Minimum Pipe Slope	0.005 ft/ft	The scalar under Min Slope Basis = Fixed Value (or the floor under Greater of Both); unused under Velocity-Based. Pipes below the resolved minimum trigger a warning.
Min Velocity	2.0 ft/s	Judged as Manning full-flow velocity Vf (flow-independent, from geometry and slope). Pipes below this trigger a compliance warning (self-cleaning velocity), and it is the basis for Velocity-Based Min Slope above.
Max Velocity	10.0 ft/s	Judged as Q ÷ Afull (discharge over the full-barrel area), independent of the flow depth actually present. Pipes exceeding this trigger a compliance warning. It gates pipe size in Auto Design — a size that clears it may still ride as steeply as cover, crossings, and HGL allow; it is never a grade limiter.
Minimum Pipe Cover	2.0 ft	Minimum clearance from ground to pipe crown.
Maximum Pipe Cover	20.0 ft	Maximum depth from ground to pipe crown.
HGL Cover	1.0 ft	Required clearance from the hydraulic grade line to ground/rim, checked at every computed storm.
Minimum Structure Depth	4.0 ft	Minimum depth from rim to lowest connected pipe invert at each access structure (manhole, inlet, junction box). Not enforced at fittings/null structures (see Fitting Keywords below) — the sizing engine never buries the barrel itself to satisfy this, only deepens the structure's sump.
Min Crossing Clearance	1.0 ft	Required vertical clearance between this network's pipes and any crossing pipe (other storm lines, or water/sewer utilities referenced through data shortcuts). Crossings with less clearance are flagged in red in the profile view, and Auto Design grades pipes to maintain this distance. Project-specific; the last value you set becomes the default for new projects.

HGL Cover (Check) is not a row in this dialog — there's no field to type it into directly — but a design standard's design criteria can carry a separate check-storm HGL cover value, which arrives (like everything else in that checklist) through the design-criteria adoption prompt when you apply the standard.

Alignment Configuration

Setting	Description
Require Alignments	When enabled, pipes must be assigned to an alignment to be included in calculations.
Alignment Sort Order	Alphabetical (by name) or Hydrologic (trunks first, then laterals downstream-to-upstream).

Alignment design types (Storm Drain / Culvert / None) are not set here — they're edited from Tables > Alignment Types.... See Alignment Design Types.

Compliance Checks

Below the Design Constraints table, every design-criteria check (velocity, cover, HGL clearance, etc.) has its own Enabled / Disabled toggle. Disabling a check removes it entirely from the Comply column: its rows in the results grid no longer factor it into the pass/total score, and its per-pipe warnings are suppressed. This is a project-wide switch; for a one-off accepted violation on a specific pipe, use the per-pipe Acknowledge Check Failures... right-click action instead, which preserves an audit trail. See Compliance Checking.

Auto Design & Matching Defaults

Setting	Default	Description
Auto Design Engine	Phased	Phased (size, then profile, then HGL) is the default; a project saved before it became the default opens on Phased too; pick Classic here to put it back. Classic is the long-standing engine. See Auto Design Engine for what each one does and does not propose. Hold-existing-grades mode (below) always runs Classic regardless of this choice.
Auto Design Grades	Design Grades	Design Grades lets Auto Design propose new inverts (the shallow-seeking, least-cost grade policy). Hold Existing Grades locks every invert to the drawing and renders size-only verdicts at the locked grade (StormCAD-style parity) — drop connections, splits, and the downstream-lowering negotiation don't apply in this mode.
Sizing Capacity Basis	HGL-Governed	Gravity Full-Flow never proposes a size where Q exceeds full-barrel capacity (no surcharge). HGL-Governed allows pressure flow when the computed HGL still clears HGL Cover below grade — common North Texas practice. Compliance-grid checks are unaffected either way.
Max Surcharge Ratio (blank = off)	Off	Optional ceiling on (HGL − crown) / rise for the Phased engine's HGL refinement, under HGL-Governed. Off by ruling: HGL cover and the velocity limits are the governing brakes; crown-referenced surcharge is not treated as its own criterion. Ignored under Gravity Full-Flow.
Auto Design Size Changes	Never	How Auto Design handles a mid-run size increase: Never split the pipe, Prompt before splitting, or split Automatically at a size-change null structure. Never by default — a break is a new structure, and the extra cost can outweigh what it saves.
Min Split Leg Length (ft)	20.0 ft	Shortest leg Auto Design will create when splitting a pipe for a size change.
Split Station Rounding (ft)	1.0 ft	Station increment new split points are rounded to (rounding up, always conservative).
Drop Connections	Not Allowed	Whether Auto Design may seat an incoming pipe above the match-criteria transition at a real structure (a drop connection), buying trench depth on the run above at the cost of a plunge in the structure. Off by default — that trade is a site/cost call for the engineer.
Max Added Drop at Structure (ft)	0 (no limit)	Largest drop Auto Design may add above the match criteria when Drop Connections is on. Bounds only the discretionary ride, never a crown/centerline match step.
Cover Grade Breaks	No	Whether Auto Design may propose same-size grade breaks that follow sampled ground under mid-span humps, to save trench depth. Off by default — a TIN surface can undulate, and an engine free to chase every dip would litter the run with break structures.
Min Grade-Break Leg Length (ft)	100.0 ft	Shortest leg a cover-following grade break may produce. Deliberately larger than Min Split Leg Length, which governs size-change splits.
Fitting Keywords	wye, bend, tee, lateral, elbow, reduce, pipe size change, PC, PT, exit, headwall, curve	Comma-separated part-description keywords, matched as whole words (so "tee" does not hit "Steel"). A match excludes the structure from the Minimum Structure Depth check and the drop-connection ride, and makes a real (non-null-structure) part eligible to be classified as a wye/bend/size-change fitting for the Lateral Match at Wyes rule below and for Label Fittings; a structure that is not a fitting falls under Lateral Match at Structures instead. Remembered as your default for new projects.
Inlet Keywords	inlet, catch basin, curb, grate, combination, CB	Comma-separated, whole-word part-description keywords that classify a structure as an inlet at import/load, and that HydraLink basin matching prefers when placing a basin.
Structure Drop (ft)	0.1 ft	Default invert drop applied at each real structure when computing pipe slopes under the Inverts match criterion.
Ignore Null Structure Drop	Yes	When Yes, the Structure Drop is not applied at null (pipe-to-pipe) structures.
Match Criteria (Slopes + Auto Design)	Inverts	Default structure transition criterion (Inverts, Centerlines, or Crowns) for new multi-pipe slope operations, and for every pipe-to-pipe transition Auto Design proposes during sizing (including a size-change split). Inverts applies the Structure Drop through the transition; Centerlines and Crowns don't.
Lateral Match at Wyes	Centerlines (new projects); Same as network (projects saved before this setting existed)	Overrides the match criterion at a wye — a null structure, auto-joint, or Fitting Keyword part with exactly two pipes in and one out. The trunk inlet (the one nearest straight-through to the outlet) always holds invert continuity, whatever this setting says; the lateral is matched by this setting instead of by Match Criteria above. Same as network turns the rule off: every incoming pipe, wye or not, follows Match Criteria. A manhole receiving a lateral is never treated as a wye, and an eligible structure with three or more inlets is reported in Network Issues rather than matched as one. Read by both Auto Design engines and the multi-pipe slope tools.
Lateral Match at Structures	Crowns (new projects); Same as network (projects saved before this setting existed)	How a lateral entering a real structure — a manhole, inlet or junction box — matches the main. The trunk inlet (the one on the outlet's alignment, else nearest straight-through) keeps Match Criteria; every other inlet steps by the larger of the Structure Drop and this match: Crowns or Centerlines gives whichever of the drop and that match is greater, Inverts the drop alone. Same as network turns the rule off. Read by both Auto Design engines and the multi-pipe slope tools. Remembered as your default for new projects: a new project starts at whatever you chose last (Crowns until you have chosen), never at a value a design standard supplies.
Auto-Update K Values	No	Whether junction Kj values recompute automatically as geometry changes.
Alignment Sort Order	Alphabetical	Alphabetical (by name) or Hydrologic (trunks first, then laterals downstream-to-upstream). Also listed under Alignment Configuration above.
Merge Splice Rows	No	When Yes, pipe-splice reaches (several real pipes shown as one continuous run) are merged into a single read-only row in the results grid.

Quantity Takeoff

Cut-depth class boundaries for the pipe linear-footage breakdown in the quantities table (Output ▾ > Tables to Drawing > Quantities Table and the Excel Quantities sheet). Cut depth is measured from the sampled surface to the flowline invert; each row is a class upper bound, and the last class is open-ended. Remove all rows to skip the depth breakdown entirely.

Design Standard (Not in This Dialog)

The active design standard (junction loss library) is not selected in Project Settings: it's chosen from the Design standard dropdown at the top of Tables > Minor Losses.... The Storm Drain tab above only reminds you of this ("Junction losses are driven by the selected design standard. Use Tables > Minor Losses... to choose or edit it."). Built-in standards include:

• User Starter — Generic loss types with simple K expressions. Good starting point for custom standards.
• HEC-22 — HEC-22 4th Edition standard types, using the 3-step access hole energy loss method for manholes.
• iSWM / NCTCOG — NCTCOG iSWM 2014 types, using the HEC-22 2nd Edition compound K method for manholes.

When a standard includes design criteria (municipality-specific defaults for storm periods, velocity limits, cover, etc.), HydraStorm prompts you with a checklist showing which settings differ from your current project. Accept or decline each recommendation individually.

Hydrology Tab

Where runoff comes from. Detailed on the Hydrology Modes and Storm Events pages. The tab has two sub-tabs, General and IDF Curves, below the hydrology mode selector. Which storms each module runs lives on that module's own tab, not here.

Hydrology Mode

Always visible at the top of the tab, as radio buttons:

Mode	Description
Peak Flows Only	Enter Q (cfs) directly at each node. No rational method.
HydraLink	Import from a HydraLink project file (.hyd or .hlresults). Selecting this mode reveals a HydraLink Integration section on the General sub-tab (file path/browse/reload, plan and primary/secondary storm selection, Import Basis, spatial match radius, and a flow-assignment review grid). Import Basis chooses what the link supplies — Basin Parameters (C·A·Tc, HydraStorm computes Q) or Fixed Flows (routed results drive Q). The linked file can force one of them, in which case the radios lock and the line beneath explains why; see Import Basis.
Manual	Enter area, C, and Tc per node for rational method calculation.

General Sub-Tab (rational options and defaults)

Hidden in Peak Flows Only mode, where there is nothing to configure: flows are entered per node on the results grid.

Setting	Default	Description
Apply Storm Frequency Adjustment Factor (Cf)	Off	Multiplies the runoff coefficient by the storm's Cf: Q = (Cf·C)·I·A. Reveals the Cf table below; see Frequency Adjustment (Cf). Disabled in HydraLink mode: the linked file's storm K factors drive it.
Apply Rational Unit Conversion Factor	Off	When checked, multiplies peak flow by the Conversion Factor (default 43,560 / 43,200 ≈ 1.0083) that converts acre·in/hr to cfs. Most engineers leave this off since the bias is <1%.
Default Inlet Time	10 min	Time of concentration for overland flow to reach the first inlet.
Default C	0.70	Default runoff coefficient applied to nodes with no basin data of their own.
Minimum Tc	0 min	Floor applied to the time of concentration before every intensity lookup. Most municipal standards floor Tc at 10 min, and NOAA Atlas 14 publishes nothing below 5 min; below the table minimum the interpolator clamps to the shortest duration and under-predicts i. 0 disables the floor.

The three defaults stay editable in HydraLink mode: they are the fallback for nodes with no matched HydraLink basin.

Storm Events

The Storm Events table is where the project's return periods are declared, one row per storm, with its C_f. Type a return period into the box below the table and click Add; Remove deletes the storm from the project and from every module that was analysing it.

This list is the single source of the project's storms. Two things follow from it:

• The Storm Drain, Culverts and Inlets tabs assign roles (design, check, analysis) by picking from this list, rather than each defining its own return periods.
• The IDF Curves sub-tab gets one intensity column per row, so a published municipal table can be entered in full, including storms you have not yet assigned to a module.

Removing a storm from a module tab only unassigns it. The storm, its C_f and its intensity column stay, so switching a module off a storm and back on again does not cost you the data.

Frequency Adjustment (C_f)

Checking Apply Storm Frequency Adjustment Factor (C_f) enables the C_f column of the Storm Events table above. This is the only place C_f is entered. Every module (storm drain, culverts, inlets) looks its C_f up there by the return period it is running at, and each module's storm grid shows the resolved value read-only.

C_f is a property of the storm, not of the analysis: a 100-year storm has the same frequency adjustment whether you are checking a trunk line, a culvert, or inlet spread. Entering it once is what keeps those runs consistent: a 100-year culvert check resolves the 100-year C_f even when the storm drain is sized for the 5-year storm.

A new storm's C_f is seeded from the TxDOT/FHWA standard values, which you can overwrite:

Return period	Cf
10-year and under	1.00
25-year	1.10
50-year	1.20
100-year and over	1.25

Unchecking the box greys the C_f column but keeps its values, so switching the adjustment back on restores what you entered. In HydraLink mode the table is read-only: the linked file's per-storm K factors own it, and HydraStorm adopts them by matching return period.

IDF Curves Sub-Tab (hidden in Peak Flows Only mode)

Configures rainfall intensity-duration-frequency data for the rational method:

• Import controls (hidden in HydraLink mode, where IDF comes from the linked file) — Latitude/Longitude fields with a Pick Point button (samples a point in the drawing), Fetch NOAA Atlas 14, and Import CSV.
• Interpolation Method — radio buttons: Log-Log (log-log interpolation on the intensity table; standard for Atlas 14 data), Linear (linear interpolation on the table), or b/d/e Coefficients (evaluates i = b / (Tc + d)^e within its fitted duration window).
• Duration / Intensity Table — editable grid of duration vs. intensity, with one column per storm on the Storm Events list, headed by return period and role. Enter a published municipal table here directly; blank cells simply omit that duration for that storm. The standard durations (5, 10, 15, 30, 60, 120, 180 min) are always present, and Add duration adds any other the manual publishes (20, 25, 40, 45, 90 min) up to 180 min. Remove on a row deletes that duration for every storm.
• b/d/e Coefficients section (shown when Coefficients mode is selected) — one editable row per storm with an R² fit-quality readout: b is the numerator, d the time shift (minutes), and e the exponent in i = b / (Tc + d)e. Generate from Table fits a curve for every storm the table has at least three durations for (durations up to 2 hours) and reports any it could not; editing a coefficient by hand resets that row's R² to “—”, since the fit statistic no longer describes the curve.
• IDF Curve chart — a log-log intensity-duration chart reflecting the current table/coefficients and interpolation method.

See the IDF Data page for more detail on each source.

Why OK Can Refuse

Clicking OK validates the hydrology configuration before committing it, and two conditions block the commit outright rather than just warning:

• A storm the IDF data can't price. If a configured storm's return period has no usable table row or coefficient fit, OK refuses and names the storm. Add the missing intensity data (or remove the storm from every module) before continuing.
• A reachable pond under a rational hydrology mode. Storage attenuates flow; Σ(C·A) does not. If a linked HydraLink pond connects to a structure HydraStorm models — the routine case of continuing the model below a detention pond — rational accumulation can't be trusted for the network, and OK refuses. The message names the pond and offers a one-click fix: point at the companion solved .hlresults file for the same plan (found automatically by its <hyd>_<plan>.hlresults name), which carries the pond's routed outflow so the trunk above it prices from that number instead of un-attenuated ΣCA. A pond at the outfall with nothing modeled below it is not "reachable" and never triggers this. Never delete the pond to work around the refusal — the storage is real; switch to a peak-flow basis or link the solved results instead. See HydraLink Integration.

Culverts Tab

Storm events for alignments classified as culverts, in the same Storm / Role / C_f grid as the storm drain (C_f read-only here too, resolved from the return period). Storms are picked from the project's Storm Events list. Leave the grid empty to run culverts on the storm drain storms.

Culvert hydraulics (HDS-5 inlet/outlet control) use the storm drain design parameters: Manning's n, tailwater method, cover. An alignment is marked as a culvert from the alignment list in the main window; see Culvert Analysis.

Design Criteria

Below the storm grid, four compliance limits for culvert crossings — separate from the storm drain's own Design Constraints on the Storm Drain tab. Each is blank by default, meaning not enforced.

Setting	Description
Max HW/D (blank = off)	Maximum headwater-to-rise ratio at the design storm.
Min Freeboard to Road, Design (ft)	Minimum clearance from the design-storm headwater to the roadway crest. Needs a roadway record (Tables > Culvert Roadways...) to evaluate; without one, an advisory reports the check was skipped rather than failing it.
Min Freeboard to Road, Check (ft)	Minimum clearance at the check storm. 0 means the road must not overtop at the check storm.
Max Outlet Velocity (ft/s)	Maximum barrel outlet velocity at the design storm.

Verdicts appear in the culvert results grid's Criteria column, in calculation messages, and in the Excel export's culvert sheet. A design standard can prescribe these values too, arriving through the same design-criteria adoption prompt as its other recommended settings. See Culvert Analysis > Design Criteria for detail, and Roadway Overtopping for the roadway record itself.

Inlets Tab

The Enable inlet design checkbox turns the module on: the Inlet tab in the main window, the inlet capacity and bypass calculations, and the storm grid below it. The storm grid works like the storm drain's, picking from the project's Storm Events list; leave it empty to run inlets on the storm drain storms.

Whether an inlet storm's captured flow feeds the pipe system is set per storm drain storm: the Inlet column on the Storm Drain tab.

Display Tab

One row per quantity (flow, velocity, elevation, …) setting the decimal places shown in the results grids, drafted CAD tables, and the Excel export. Display only. Calculations always use full precision. Default keeps each output's built-in format, which can differ per column; picking a number makes every output agree on that quantity.

The Station row is the one exception: stations always render in plan-and-profile "+" notation (e.g. 12+34.56), on the results grid, the drafted storm-calcs CAD table, and the Excel workbook alike, and the "+" itself never changes. What the Station row sets is the number of digits after the plus — the same row reads 12+34.6 at one digit. Default is two digits, matching the Civil 3D display convention.

Profile view colors, line styles, and overlays are per-user and live on View ▾ > View Settings, not here.

Not in This Dialog

• Label styles — picking and applying them is one action on Output ▾ > Apply Label Styles…. See Profiles & Labels.
• HGL profile creation — Output ▾ > Create HGL Profiles... opens an options dialog for storm selection, profile style, and full vs. Simple HGL.
• Design standard — the Design standard dropdown (and Manage button) at the top of Tables > Minor Losses....
• Inlet library — the Inlet tab's Library... button.