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Precipitation Hyetograph Generation - Complete Method Comparison

Purpose

This notebook demonstrates all precipitation hyetograph generation methods available in ras-commander, comparing their characteristics, use cases, and when to use each.

Test Location

Houston, TX: Latitude 29.76°, Longitude -95.37°

Verify precipitation values: NOAA Atlas 14 PFDS - Houston, TX

Click the link above to verify the Atlas 14 precipitation depths used in this notebook match the official NOAA values.

Available Methods

ras-commander provides six tools for precipitation workflows:

Hyetograph Generation Methods (4 methods)

Method Algorithm HMS Equiv Depth Conservation Durations Peak Control Use Case
StormGenerator Alternating Block (Chow 1988) NO Exact Any Flexible (0-100%) Custom peak positioning
Atlas14Storm NOAA temporal distributions YES 10^-6 6h, 12h, 24h, 96h Fixed (quartile) Modern Atlas 14, regulatory
FrequencyStorm TP-40 pattern YES 10^-6 6-48hr Variable TP-40 legacy data, Houston area
ScsTypeStorm SCS TR-55 curves YES 10^-6 24hr only Fixed (type) SCS Type I/IA/II/III

Spatial PFE Tools (2 tools)

Tool Purpose Data Source Use Case
Atlas14Grid Gridded PFE access NOAA CONUS NetCDF Spatially variable rainfall
Atlas14Variance Variance analysis Statistical methods Uniform vs distributed decision

Method Selection Decision Tree

Text Only
Need precipitation hyetograph for HEC-RAS?
|
+-- Need HMS-equivalent results? (regulatory, HMS-RAS coordination)
|   |
|   +-- Modern Atlas 14 data (6h, 12h, 24h, 96h)?
|   |   +-- Use Atlas14Storm (NOAA temporal distributions)
|   |
|   +-- TP-40 or need 48hr duration?
|   |   +-- Use FrequencyStorm (M3-validated pattern)
|   |
|   +-- SCS Type I, IA, II, or III (24hr)?
|       +-- Use ScsTypeStorm (TR-55 validated)
|
+-- Need flexible peak positioning (0-100%)?
|   +-- Use StormGenerator (Alternating Block Method)
|
+-- Need spatially distributed PFE values?
|   +-- Use Atlas14Grid
|
+-- Need to check if uniform rainfall is appropriate?
    +-- Use Atlas14Variance (see 725_atlas14_spatial_variance.ipynb)

HMS Validation Summary

Three HMS-validated methods are available:

Method Validation Source Precision Documentation
Atlas14Storm HEC-HMS 4.13 DSS comparison < 10^-6 inch 6 comprehensive proofs
FrequencyStorm TP-40 pattern HMS output < 10^-6 inch M3 output validation
ScsTypeStorm HEC-HMS 4.13 source extraction < 10^-6 inch TR-55 peak timing

Known Limitations

  • 48-hour Atlas14Storm: NOAA doesn't publish 48h temporal CSVs. Use FrequencyStorm as workaround.
  • ScsTypeStorm duration: HMS constrains SCS types to 24hr only.
  • StormGenerator: NOT HMS-equivalent (different algorithm), but conserves user-specified depth exactly.

References

  • NOAA Atlas 14 PFDS: https://hdsc.nws.noaa.gov/pfds/pfds_map_cont.html
  • Chow, V.T., Maidment, D.R., Mays, L.W. (1988). Applied Hydrology. McGraw-Hill. Section 14.4
  • NRCS TR-55: SCS Type distributions
  • HEC-HMS Technical Reference Manual: Frequency Storm methodology

Setup and Imports

Python
# =============================================================================
# DEVELOPMENT MODE TOGGLE
# =============================================================================
USE_LOCAL_SOURCE = True  # Set to True for local development, False for pip package

if USE_LOCAL_SOURCE:
    import sys
    from pathlib import Path
    local_path = str(Path.cwd().parent)
    if local_path not in sys.path:
        sys.path.insert(0, local_path)
    print(f"LOCAL SOURCE MODE: Loading from {local_path}/ras_commander")
else:
    print("PIP PACKAGE MODE: Loading installed ras-commander")

# Import all precipitation modules
from ras_commander.precip import (
    StormGenerator,                # Alternating Block Method
    Atlas14Storm,                  # HMS-equivalent Atlas 14 temporal distributions
    FrequencyStorm,                # HMS-equivalent TP-40 temporal pattern
    ScsTypeStorm,                  # HMS-equivalent SCS Type I/IA/II/III
    Atlas14Grid,                   # Gridded PFE access
    Atlas14Variance,               # Spatial variance analysis
    ATLAS14_AVAILABLE,             # Availability flag for Atlas14Storm
    FREQUENCY_STORM_AVAILABLE,     # Availability flag for FrequencyStorm
    SCS_TYPE_AVAILABLE             # Availability flag for ScsTypeStorm
)

import ras_commander
print(f"Loaded ras_commander: {ras_commander.__file__}")

# Check HMS-equivalent method availability (all require hms-commander)
print(f"\nHMS-Equivalent Methods:")
if ATLAS14_AVAILABLE:
    print("  [OK] Atlas14Storm available (Atlas 14 temporal distributions)")
else:
    print("  [--] Atlas14Storm NOT available")

if FREQUENCY_STORM_AVAILABLE:
    print("  [OK] FrequencyStorm available (TP-40 temporal pattern)")
else:
    print("  [--] FrequencyStorm NOT available")

if SCS_TYPE_AVAILABLE:
    print("  [OK] ScsTypeStorm available (SCS Type I/IA/II/III)")
else:
    print("  [--] ScsTypeStorm NOT available")

if not (ATLAS14_AVAILABLE or FREQUENCY_STORM_AVAILABLE or SCS_TYPE_AVAILABLE):
    print("\n  Install hms-commander for HMS-equivalent methods:")
    print("  pip install hms-commander")
Text Only
LOCAL SOURCE MODE: Loading from c:\GH\ras-commander/ras_commander
Loaded ras_commander: c:\GH\ras-commander\ras_commander\__init__.py

HMS-Equivalent Methods:
  [OK] Atlas14Storm available (Atlas 14 temporal distributions)
  [OK] FrequencyStorm available (TP-40 temporal pattern)
  [OK] ScsTypeStorm available (SCS Type I/IA/II/III)
Python
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
from pathlib import Path

# Configure output
pd.set_option('display.max_rows', 30)
pd.set_option('display.float_format', '{:.6f}'.format)  # 6 decimals for precision comparison

# =============================================================================
# TEST LOCATION - Houston, TX (Atlas 14 Volume 11, Region 3)
# =============================================================================
LATITUDE = 29.76
LONGITUDE = -95.37
STATE = "tx"
REGION = 3

# Storm parameters
TOTAL_DURATION_MIN = 1440    # 24 hours
TIME_INTERVAL_MIN = 60       # 1-hour intervals
PEAK_POSITION = 50           # 50% = centered peak

# AEP/ARI mapping
TEST_AEP = 1.0               # 1% AEP
TEST_ARI = 100               # 100-year storm
TOTAL_DEPTH_INCHES = 17.0    # From Atlas 14 for Houston 100-yr, 24-hr

print(f"Test Location: ({LATITUDE}, {LONGITUDE}) - Houston, TX")
print(f"Storm Parameters: {TOTAL_DURATION_MIN/60:.0f}-hour, {TEST_ARI}-year ({TEST_AEP}% AEP)")
print(f"Atlas 14 Total Depth: {TOTAL_DEPTH_INCHES} inches")
print(f"Verify at: https://hdsc.nws.noaa.gov/pfds/pfds_map_cont.html?lat={LATITUDE}&lon={LONGITUDE}")
Text Only
Test Location: (29.76, -95.37) - Houston, TX
Storm Parameters: 24-hour, 100-year (1.0% AEP)
Atlas 14 Total Depth: 17.0 inches
Verify at: https://hdsc.nws.noaa.gov/pfds/pfds_map_cont.html?lat=29.76&lon=-95.37

Part 1: StormGenerator (Alternating Block Method)

Method: Standard Alternating Block (Chow, Maidment, Mays 1988)

StormGenerator uses the Alternating Block Method from Applied Hydrology (Section 14.4) to generate design storm hyetographs. This method: - Uses DDF data for the temporal pattern (shape) - Scales the pattern to match the user-specified total depth - Arranges depths in alternating pattern around peak position

Key Features: - Flexible peak positioning (0-100%) - User-specified total depth (exact conservation) - DDF data used only for temporal pattern, NOT depth values - NOT HMS-equivalent (different algorithm than HMS "Frequency Storm")

Python
# =============================================================================
# 1.1 Download Atlas 14 Data for StormGenerator
# =============================================================================
print("Downloading Atlas 14 data from NOAA for StormGenerator...")

try:
    gen = StormGenerator.download_from_coordinates(
        lat=LATITUDE,
        lon=LONGITUDE,
        data='depth',
        units='english',
        series='pds'
    )
    print()
    print("[OK] Downloaded successfully!")
    print(f"  Available ARIs: {gen.ari_columns}")
    print(f"  Durations: {len(gen.durations_hours)} values")

    # Show sample depths for 100-year
    print()
    print(f"  Sample depths for {TEST_ARI}-year storm:")
    for dur in [1, 6, 12, 24]:
        idx = np.argmin(np.abs(gen.durations_hours - dur))
        depth = gen.data.iloc[idx][str(TEST_ARI)]
        print(f"    {dur:2d}-hr: {depth:.2f} inches")

    # Note: StormGenerator interpolates from DDF table (may differ from Atlas 14)
    print()
    print(f"Note: StormGenerator interpolates from DDF table showing {gen.data.iloc[np.argmin(np.abs(gen.durations_hours - 24))][str(TEST_ARI)]:.2f} inches")
    print(f"      All methods will use Atlas 14 value ({TOTAL_DEPTH_INCHES} inches) for comparison.")
    print(f"      StormGenerator deviation demonstrates interpolation differences.")

    STORM_GEN_AVAILABLE = True

except Exception as e:
    print(f"[!!] Error downloading: {e}")
    print("NOAA API may be unavailable.")
    STORM_GEN_AVAILABLE = False
Text Only
2026-01-23 22:10:52 - ras_commander.precip.StormGenerator - INFO - Downloading Atlas 14 data for (29.76, -95.37)...
2026-01-23 22:10:52 - ras_commander.precip.StormGenerator - INFO - Downloading Atlas 14 data for (29.76, -95.37)...


Downloading Atlas 14 data from NOAA for StormGenerator...


2026-01-23 22:10:54 - ras_commander.precip.StormGenerator - INFO - Downloaded Atlas 14 data for region: Texas
2026-01-23 22:10:54 - ras_commander.precip.StormGenerator - INFO - Downloaded Atlas 14 data for region: Texas



[OK] Downloaded successfully!
[!!] Error downloading: 'DataFrame' object has no attribute 'ari_columns'
NOAA API may be unavailable.
Python
# =============================================================================
# 1.2 Generate Hyetograph using Alternating Block Method
# =============================================================================
if STORM_GEN_AVAILABLE:
    print(f"Generating {TEST_ARI}-year, {TOTAL_DURATION_MIN/60:.0f}-hour hyetograph...")
    print(f"  Peak position: {PEAK_POSITION}% (centered)")
    print(f"  Target depth: {TOTAL_DEPTH_INCHES} inches (Atlas 14)")

    hyeto_ab = gen.generate_hyetograph(
        total_depth_inches=TOTAL_DEPTH_INCHES,
        duration_hours=TOTAL_DURATION_MIN / 60,
        position_percent=PEAK_POSITION,
        method='alternating_block'
    )

    # Results summary
    total_depth_ab = hyeto_ab['cumulative_depth'].iloc[-1]
    peak_intensity_ab = hyeto_ab['incremental_depth'].max()
    peak_hour_ab = hyeto_ab.loc[hyeto_ab['incremental_depth'].idxmax(), 'hour']

    print(f"\n[OK] Generated {len(hyeto_ab)} intervals")
    print(f"  Total depth: {total_depth_ab:.6f} inches")
    print(f"  Peak intensity: {peak_intensity_ab:.4f} inches")
    print(f"  Peak at hour: {peak_hour_ab:.1f}")

    # Depth conservation check (should match exactly now)
    depth_error_ab = abs(total_depth_ab - TOTAL_DEPTH_INCHES)
    print(f"\n  Depth conservation error: {depth_error_ab:.9f} inches")
    print(f"  Depth Conservation: {'VERIFIED' if depth_error_ab < 1e-6 else 'CHECK'}")

    display(hyeto_ab.head(10))
Python
# =============================================================================
# 1.3 Flexible Peak Positioning Demo
# =============================================================================
if STORM_GEN_AVAILABLE:
    # Generate with different peak positions
    peak_positions = [25, 50, 75]  # Early, centered, late
    hyetos_by_position = {}

    print("Generating hyetographs with different peak positions...")

    for pos in peak_positions:
        hyeto_pos = gen.generate_hyetograph(
            total_depth_inches=TOTAL_DEPTH_INCHES,
            duration_hours=24,
            position_percent=pos
        )
        hyetos_by_position[pos] = hyeto_pos

        peak_hour_pos = hyeto_pos.loc[hyeto_pos['incremental_depth'].idxmax(), 'hour']
        total_pos = hyeto_pos['cumulative_depth'].iloc[-1]
        print(f"  {pos}% position: Peak at hour {peak_hour_pos:.1f}, Total: {total_pos:.6f} in")

    # Visualize
    fig, ax = plt.subplots(figsize=(12, 6))

    colors = ['blue', 'green', 'orange']
    for (pos, hyeto_pos), color in zip(hyetos_by_position.items(), colors):
        ax.bar(hyeto_pos['hour'], hyeto_pos['incremental_depth'], 
               width=0.8, alpha=0.4, label=f'{pos}% peak position', color=color)

    ax.set_xlabel('Time (hours)', fontsize=11)
    ax.set_ylabel('Incremental Depth (inches)', fontsize=11)
    ax.set_title(f'StormGenerator: Flexible Peak Positioning\n(Alternating Block Method - {TOTAL_DEPTH_INCHES} inches total)', 
                 fontsize=12, fontweight='bold')
    ax.legend(loc='upper right')
    ax.grid(True, alpha=0.3)

    plt.tight_layout()
    plt.show()

    print("\n[OK] StormGenerator allows flexible peak positioning (0-100%)")
    print("  All positions conserve the specified total depth exactly.")

Part 2: Atlas14Storm (HMS-Equivalent - Modern Atlas 14)

Validation Status: [OK] FULLY CERTIFIED - HEC-HMS ground truth at 10^-6 precision

Atlas14Storm uses official NOAA Atlas 14 temporal distribution curves to generate hyetographs that exactly match HEC-HMS "Specified Pattern" results.

Key Features: - Uses official NOAA temporal distributions (same as HMS internally) - Perfect depth conservation (< 10^-6 inch error) - Supports all 5 quartiles (First, Second, Third, Fourth, All Cases) - Supports multiple durations: 6h, 12h, 24h, 96h (48h NOT available - use FrequencyStorm) - Validated against HEC-HMS ground truth (6 comprehensive proofs)

Validation Documentation: hms-commander/examples/08_atlas14_hyetograph_generation.ipynb

Python
# =============================================================================
# 2.1 Generate HMS-Equivalent Hyetograph (24-hour)
# =============================================================================
if ATLAS14_AVAILABLE:
    print(f"Generating HMS-equivalent {TEST_ARI}-year, 24-hour hyetograph...")
    print(f"  State: {STATE}, Region: {REGION}")
    print(f"  Total depth: {TOTAL_DEPTH_INCHES} inches (Atlas 14)")
    print(f"  Quartile: All Cases")

    hyeto_a14 = Atlas14Storm.generate_hyetograph(
        total_depth_inches=TOTAL_DEPTH_INCHES,
        state=STATE,
        region=REGION,
        aep_percent=TEST_AEP,
        quartile="All Cases"
    )

    # Results summary
    total_depth_a14 = hyeto_a14['incremental_depth'].sum()
    peak_intensity_a14 = hyeto_a14['incremental_depth'].max()
    peak_idx_a14 = hyeto_a14['incremental_depth'].idxmax()
    peak_hour_a14 = peak_idx_a14 * 0.5  # 30-minute intervals

    print(f"\n[OK] Generated {len(hyeto_a14)} intervals (30-minute)")
    print(f"  Total depth: {total_depth_a14:.6f} inches")
    print(f"  Peak intensity: {peak_intensity_a14:.4f} inches")
    print(f"  Peak at hour: {peak_hour_a14:.1f}")

    # Depth conservation check (10^-6 precision)
    depth_error_a14 = abs(total_depth_a14 - TOTAL_DEPTH_INCHES)
    print(f"\n  Depth conservation error: {depth_error_a14:.9f} inches")
    print(f"  HMS EQUIVALENCE: {'VERIFIED' if depth_error_a14 < 1e-6 else 'FAILED'} (< 10^-6 inch)")

else:
    print("[!!] Atlas14Storm not available - install hms-commander")
    print("   pip install hms-commander")
Text Only
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: C:\Users\bill\.hms-commander\atlas14\tx_3_24h_temporal.csv
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: C:\Users\bill\.hms-commander\atlas14\tx_3_24h_temporal.csv
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Parsed 5 quartile tables with 49 time steps each
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Parsed 5 quartile tables with 49 time steps each
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 17.000 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 17.000 inches total


Generating HMS-equivalent 100-year, 24-hour hyetograph...
  State: tx, Region: 3
  Total depth: 17.0 inches (Atlas 14)
  Quartile: All Cases

[OK] Generated 49 intervals (30-minute)
  Total depth: 17.000000 inches
  Peak intensity: 1.5555 inches
  Peak at hour: 1.5

  Depth conservation error: 0.000000000 inches
  HMS EQUIVALENCE: VERIFIED (< 10^-6 inch)
Python
# =============================================================================
# 2.2 All 5 Quartiles Demo
# =============================================================================
if ATLAS14_AVAILABLE:
    quartiles = ["First Quartile", "Second Quartile", "Third Quartile", "Fourth Quartile", "All Cases"]
    hyetos_quartile = {}

    print("Generating hyetographs for all 5 quartiles...")
    print(f"{'Quartile':<20s} {'Peak Hour':>10s} {'Peak (in)':>10s} {'Depth Error':>15s}")
    print("-" * 60)

    for q in quartiles:
        hyeto_q = Atlas14Storm.generate_hyetograph(
            total_depth_inches=TOTAL_DEPTH_INCHES,
            state=STATE,
            region=REGION,
            aep_percent=TEST_AEP,
            quartile=q
        )
        hyetos_quartile[q] = hyeto_q

        peak_idx_q = hyeto_q['incremental_depth'].idxmax()
        peak_hour_q = peak_idx_q * 0.5
        depth_err_q = abs(hyeto_q['incremental_depth'].sum() - TOTAL_DEPTH_INCHES)

        print(f"{q:<20s} {peak_hour_q:>10.1f} {hyeto_q['incremental_depth'].max():>10.4f} {depth_err_q:>15.9f}")

    print("\n[OK] All 5 quartiles conserve depth at 10^-6 precision")
    print("\nQuartile Selection Guide:")
    print("  First Quartile  -> Early peak (conservative for upstream)")
    print("  Fourth Quartile -> Late peak (conservative for downstream)")
    print("  All Cases       -> Median pattern (standard design)")

    # Visualize all quartiles
    fig, ax = plt.subplots(figsize=(14, 7))

    time_hours_a14 = np.arange(len(hyetos_quartile["All Cases"])) * 0.5
    colors = ['blue', 'green', 'orange', 'red', 'black']

    for (q, hyeto_q), color in zip(hyetos_quartile.items(), colors):
        ax.plot(time_hours_a14, hyeto_q['incremental_depth'], linewidth=2, label=q, color=color, alpha=0.7)

    ax.set_xlabel('Time (hours)', fontsize=12)
    ax.set_ylabel('Incremental Depth (inches)', fontsize=12)
    ax.set_title(f'Atlas14Storm: All 5 Quartile Temporal Distributions\n{TEST_ARI}-Year, 24-Hour Storm - Houston, TX (HMS-Equivalent)', 
                 fontsize=12, fontweight='bold')
    ax.legend(loc='upper right')
    ax.grid(True, alpha=0.3)

    plt.tight_layout()
    plt.show()
Text Only
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: tx_3_24h
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: tx_3_24h
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 17.000 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 17.000 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: tx_3_24h
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: tx_3_24h
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 17.000 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 17.000 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: tx_3_24h
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: tx_3_24h
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 17.000 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 17.000 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: tx_3_24h
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: tx_3_24h
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 17.000 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 17.000 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: tx_3_24h
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: tx_3_24h
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 17.000 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 17.000 inches total


Generating hyetographs for all 5 quartiles...
Quartile              Peak Hour  Peak (in)     Depth Error
------------------------------------------------------------
First Quartile              1.0     2.1879     0.000000000
Second Quartile             7.5     1.2427     0.000000000
Third Quartile             14.0     0.9894     0.000000000
Fourth Quartile             0.5     1.2818     0.000000000
All Cases                   1.5     1.5555     0.000000000

[OK] All 5 quartiles conserve depth at 10^-6 precision

Quartile Selection Guide:
  First Quartile  -> Early peak (conservative for upstream)
  Fourth Quartile -> Late peak (conservative for downstream)
  All Cases       -> Median pattern (standard design)

png

Python
# =============================================================================
# 2.3 Multi-Duration Demo (6h, 12h, 24h, 96h)
# =============================================================================
if ATLAS14_AVAILABLE:
    # Get actual Atlas 14 depths from the downloaded DDF table
    # (StormGenerator downloaded this in the imports cell)
    if '_gen' in dir() and _gen is not None:
        durations_a14 = {}
        for dur_hr in [6, 12, 24, 96]:
            idx = np.argmin(np.abs(_gen.durations_hours - dur_hr))
            durations_a14[dur_hr] = float(_gen.data.iloc[idx][str(TEST_ARI)])
        print(f"Using actual Atlas 14 depths from NOAA API:")
        for dur_hr, depth in durations_a14.items():
            print(f"  {dur_hr:3d}-hr: {depth:.2f} inches")
    else:
        # Fallback values (verified from NOAA for Houston 100-yr)
        durations_a14 = {
            6: 9.56,      # 6-hour depth (Houston 100-yr)
            12: 11.7,     # 12-hour depth
            24: 14.1,     # 24-hour depth
            96: 19.3      # 96-hour depth
        }
        print("Using fallback Atlas 14 depths (NOAA API not available)")

    print()
    print("Atlas14Storm Multi-Duration Demo")
    print("="*70)
    print(f"{'Duration':<12s} {'Steps':>8s} {'Total Depth':>15s} {'Depth Error':>15s} {'HMS Equiv':>12s}")
    print("-"*70)

    hyetos_multidur_a14 = {}

    for dur_hr, depth in durations_a14.items():
        try:
            hyeto_dur = Atlas14Storm.generate_hyetograph(
                total_depth_inches=depth,
                state=STATE,
                region=REGION,
                duration_hours=dur_hr,
                aep_percent=TEST_AEP,
                quartile="All Cases"
            )
            hyetos_multidur_a14[dur_hr] = hyeto_dur

            depth_err = abs(hyeto_dur['incremental_depth'].sum() - depth)
            hms_equiv = "VERIFIED" if depth_err < 1e-6 else "FAILED"

            print(f"{dur_hr:>3d}h         {len(hyeto_dur):>8d} {hyeto_dur['incremental_depth'].sum():>15.6f} {depth_err:>15.9f} {hms_equiv:>12s}")

        except Exception as e:
            print(f"{dur_hr:>3d}h         {'N/A':>8s} {'N/A':>15s} {str(e)[:30]:>30s}")

    print("-"*70)
    print("\nNote: 48h duration NOT available in Atlas14Storm (NOAA limitation)")
    print("      Use FrequencyStorm for 48-hour storms.")

    # Visualize multi-duration
    if len(hyetos_multidur_a14) > 1:
        fig, axes = plt.subplots(2, 2, figsize=(14, 10))
        axes = axes.flatten()

        for idx, (dur_hr, hyeto_dur) in enumerate(hyetos_multidur_a14.items()):
            ax = axes[idx]
            time_hours = hyeto_dur['hour']
            ax.bar(time_hours, hyeto_dur['incremental_depth'], width=0.4, alpha=0.7, color='steelblue')
            ax.set_xlabel('Time (hours)')
            ax.set_ylabel('Incremental Depth (in)')
            ax.set_title(f'{dur_hr}-Hour Storm ({durations_a14[dur_hr]:.1f} in total)')
            ax.grid(True, alpha=0.3)

        plt.suptitle('Atlas14Storm: Multi-Duration HMS-Equivalent Storms', fontsize=14, fontweight='bold')
        plt.tight_layout()
        plt.show()
Text Only
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: C:\Users\bill\.hms-commander\atlas14\tx_3_6h_temporal.csv
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: C:\Users\bill\.hms-commander\atlas14\tx_3_6h_temporal.csv
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Parsed 5 quartile tables with 13 time steps each
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Parsed 5 quartile tables with 13 time steps each
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 13 intervals, 9.560 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 13 intervals, 9.560 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: C:\Users\bill\.hms-commander\atlas14\tx_3_12h_temporal.csv


Using fallback Atlas 14 depths (NOAA API not available)

Atlas14Storm Multi-Duration Demo
======================================================================
Duration        Steps     Total Depth     Depth Error    HMS Equiv
----------------------------------------------------------------------
  6h               13        9.560000     0.000000000     VERIFIED


2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: C:\Users\bill\.hms-commander\atlas14\tx_3_12h_temporal.csv
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Parsed 5 quartile tables with 25 time steps each
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Parsed 5 quartile tables with 25 time steps each
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 25 intervals, 11.700 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 25 intervals, 11.700 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: tx_3_24h
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: tx_3_24h
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 14.100 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 49 intervals, 14.100 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: C:\Users\bill\.hms-commander\atlas14\tx_3_96h_temporal.csv
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Using cached temporal distribution: C:\Users\bill\.hms-commander\atlas14\tx_3_96h_temporal.csv
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Parsed 5 quartile tables with 97 time steps each
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Parsed 5 quartile tables with 97 time steps each
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 97 intervals, 19.300 inches total
2026-01-23 22:10:54 - hms_commander.Atlas14Storm - INFO - Generated hyetograph: 97 intervals, 19.300 inches total


 12h               25       11.700000     0.000000000     VERIFIED
 24h               49       14.100000     0.000000000     VERIFIED
 96h               97       19.300000     0.000000000     VERIFIED
----------------------------------------------------------------------

Note: 48h duration NOT available in Atlas14Storm (NOAA limitation)
      Use FrequencyStorm for 48-hour storms.

png

Part 3: FrequencyStorm (HMS-Equivalent - TP-40)

Validation Status: [OK] VALIDATED - HEC-HMS ground truth at 10^-6 precision

FrequencyStorm uses a TP-40/Hydro-35 temporal pattern extracted from HCFCD M3 Model D (Brays Bayou) that matches HEC-HMS "User Specified Pattern" method.

Key Features: - TP-40 pattern compatible (Houston area) - Variable duration support (6hr to 48hr validated) - Variable peak positioning (default 67%) - HMS "User Specified Pattern" equivalence proven - Fills the 48-hour gap that Atlas14Storm cannot cover

Validation: RMSE < 10^-6 inches vs HCFCD M3 Model D HMS output

Python
# =============================================================================
# 3.1 Generate TP-40 Hyetograph
# =============================================================================
if FREQUENCY_STORM_AVAILABLE:
    print("Generating TP-40 hyetograph...")
    print(f"  Total depth: {TOTAL_DEPTH_INCHES} inches (Atlas 14)")
    print(f"  Duration: 24 hours (1440 minutes)")
    print(f"  Interval: 5 minutes (TP-40 default)")
    print(f"  Peak position: 67% (TP-40 default)")

    hyeto_freq = FrequencyStorm.generate_hyetograph(
        total_depth_inches=TOTAL_DEPTH_INCHES,
        total_duration_min=1440,  # 24 hours
        time_interval_min=5,      # 5-minute intervals
        peak_position_pct=67.0    # TP-40 standard
    )

    # Results summary
    total_depth_freq = hyeto_freq['incremental_depth'].sum()
    peak_intensity_freq = hyeto_freq['incremental_depth'].max()
    peak_idx_freq = hyeto_freq['incremental_depth'].idxmax()
    peak_hour_freq = peak_idx_freq * 5 / 60  # 5-minute intervals to hours

    print(f"\n[OK] Generated {len(hyeto_freq)} intervals (5-minute)")
    print(f"  Total depth: {total_depth_freq:.6f} inches")
    print(f"  Peak intensity: {peak_intensity_freq:.4f} inches")
    print(f"  Peak at hour: {peak_hour_freq:.1f} ({peak_idx_freq*5} min, ~67% of 24hr)")

    # Depth conservation check (10^-6 precision)
    depth_error_freq = abs(total_depth_freq - TOTAL_DEPTH_INCHES)
    print(f"\n  Depth conservation error: {depth_error_freq:.9f} inches")
    print(f"  HMS EQUIVALENCE: {'VERIFIED' if depth_error_freq < 1e-6 else 'FAILED'} (< 10^-6 inch)")

    # Note on temporal pattern
    print(f"\nNote: Uses TP-40/Hydro-35 pattern (Houston area)")
    print(f"      Pattern validated to match HMS 'User Specified Pattern' at 10^-6 precision")

else:
    print("[!!] FrequencyStorm not available - install hms-commander")
    print("   pip install hms-commander")
Text Only
Generating TP-40 hyetograph...
  Total depth: 17.0 inches (Atlas 14)
  Duration: 24 hours (1440 minutes)
  Interval: 5 minutes (TP-40 default)
  Peak position: 67% (TP-40 default)

[OK] Generated 289 intervals (5-minute)
  Total depth: 17.000000 inches
  Peak intensity: 1.5454 inches
  Peak at hour: 16.1 (965 min, ~67% of 24hr)

  Depth conservation error: 0.000000000 inches
  HMS EQUIVALENCE: VERIFIED (< 10^-6 inch)

Note: Uses TP-40/Hydro-35 pattern (Houston area)
      Pattern validated to match HMS 'User Specified Pattern' at 10^-6 precision
Python
# =============================================================================
# 3.2 Variable Duration Demo (6h, 12h, 24h, 48h)
# =============================================================================
if FREQUENCY_STORM_AVAILABLE:
    # Get actual Atlas 14 depths from the downloaded DDF table
    if '_gen' in dir() and _gen is not None:
        durations_freq = {}
        for dur_hr, dur_min in [(6, 360), (12, 720), (24, 1440), (48, 2880)]:
            idx = np.argmin(np.abs(_gen.durations_hours - dur_hr))
            durations_freq[dur_hr] = (dur_min, float(_gen.data.iloc[idx][str(TEST_ARI)]))
        print("Using actual Atlas 14 depths from NOAA API:")
        for dur_hr, (dur_min, depth) in durations_freq.items():
            print(f"  {dur_hr:3d}-hr: {depth:.2f} inches")
    else:
        # Fallback values (verified from NOAA for Houston 100-yr)
        durations_freq = {
            6: (360, 9.56),       # 6-hour (360 min), depth
            12: (720, 11.7),      # 12-hour
            24: (1440, 14.1),     # 24-hour
            48: (2880, 17.0)      # 48-hour
        }
        print("Using fallback Atlas 14 depths (NOAA API not available)")

    print()
    print("FrequencyStorm Multi-Duration Demo")
    print("="*70)
    print(f"{'Duration':<12s} {'Steps':>8s} {'Total Depth':>15s} {'Depth Error':>15s} {'HMS Equiv':>12s}")
    print("-"*70)

    hyetos_multidur_freq = {}

    for dur_hr, (dur_min, depth) in durations_freq.items():
        try:
            hyeto_dur = FrequencyStorm.generate_hyetograph(
                total_depth_inches=depth,
                total_duration_min=dur_min,
                time_interval_min=5,
                peak_position_pct=67.0
            )
            hyetos_multidur_freq[dur_hr] = hyeto_dur

            depth_err = abs(hyeto_dur['incremental_depth'].sum() - depth)
            hms_equiv = "VERIFIED" if depth_err < 1e-6 else "FAILED"

            note = " (fills Atlas14 gap!)" if dur_hr == 48 else ""
            print(f"{dur_hr:>3d}h         {len(hyeto_dur):>8d} {hyeto_dur['incremental_depth'].sum():>15.6f} {depth_err:>15.9f} {hms_equiv:>12s}{note}")

        except Exception as e:
            print(f"{dur_hr:>3d}h         {'N/A':>8s} {'N/A':>15s} {str(e)[:30]:>30s}")

    print("-"*70)
    print("\n[OK] FrequencyStorm provides 48h coverage that Atlas14Storm lacks!")

    # Visualize multi-duration
    if len(hyetos_multidur_freq) > 1:
        fig, axes = plt.subplots(2, 2, figsize=(14, 10))
        axes = axes.flatten()

        for idx, (dur_hr, hyeto_dur) in enumerate(hyetos_multidur_freq.items()):
            ax = axes[idx]
            time_hours = hyeto_dur['hour']  # 5-min intervals to hours
            ax.bar(time_hours, hyeto_dur['incremental_depth'], width=5/60*0.8, alpha=0.7, color='darkgreen')
            ax.set_xlabel('Time (hours)')
            ax.set_ylabel('Incremental Depth (in)')
            title_note = " [Fills 48h Gap!]" if dur_hr == 48 else ""
            ax.set_title(f'{dur_hr}-Hour Storm ({durations_freq[dur_hr][1]:.1f} in total){title_note}')
            ax.grid(True, alpha=0.3)

        plt.suptitle('FrequencyStorm: Multi-Duration HMS-Equivalent Storms (TP-40)', fontsize=14, fontweight='bold')
        plt.tight_layout()
        plt.show()
Text Only
Using fallback Atlas 14 depths (NOAA API not available)

FrequencyStorm Multi-Duration Demo
======================================================================
Duration        Steps     Total Depth     Depth Error    HMS Equiv
----------------------------------------------------------------------
  6h               73        9.560000     0.000000000     VERIFIED
 12h              145       11.700000     0.000000000     VERIFIED
 24h              289       14.100000     0.000000000     VERIFIED
 48h              577       17.000000     0.000000000     VERIFIED (fills Atlas14 gap!)
----------------------------------------------------------------------

[OK] FrequencyStorm provides 48h coverage that Atlas14Storm lacks!

png

Part 4: ScsTypeStorm (HMS-Equivalent - SCS Type I/IA/II/III)

Validation Status: [OK] VALIDATED - Extracted from HEC-HMS 4.13 source code

ScsTypeStorm provides NRCS (SCS) Type I, IA, II, and III temporal distributions that match HEC-HMS exactly.

Key Features: - All 4 SCS types extracted from HMS 4.13 JAR files - Perfect depth conservation (< 10^-6 inch error) - Peak positions match TR-55 specifications - 24-hour duration only (HMS constraint - cannot be customized)

SCS Type Regional Guide

Type Region Peak Position Description
Type I Pacific maritime (interior) ~42% Early peak, slow recession
Type IA Coastal areas, Atlantic/Gulf ~33% More uniform distribution
Type II Most of CONUS ~50% Standard design storm
Type III Gulf Coast, Florida ~50% Very intense peak

Validation Source: hms-commander/examples/10_scs_type_validation.ipynb

Python
# =============================================================================
# 4.1 Generate SCS Type II Storm (Most Common)
# =============================================================================
if SCS_TYPE_AVAILABLE:
    print("Generating SCS Type II storm (most common in CONUS)...")
    print(f"  Total depth: {TOTAL_DEPTH_INCHES} inches (Atlas 14)")
    print(f"  Duration: 24 hours (HMS constraint)")
    print(f"  Interval: 60 minutes")
    print(f"  Type: II (standard design storm)")

    hyeto_scs2 = ScsTypeStorm.generate_hyetograph(
        total_depth_inches=TOTAL_DEPTH_INCHES,
        scs_type='II',
        time_interval_min=60
    )

    # Results summary
    total_depth_scs = hyeto_scs2['incremental_depth'].sum()
    peak_intensity_scs = hyeto_scs2['incremental_depth'].max()
    peak_idx_scs = hyeto_scs2['incremental_depth'].idxmax()
    peak_hour_scs = peak_idx_scs * 1.0  # 60-minute intervals
    peak_position_pct = (peak_hour_scs / 24) * 100

    print(f"\n[OK] Generated {len(hyeto_scs2)} intervals (60-minute)")
    print(f"  Total depth: {total_depth_scs:.6f} inches")
    print(f"  Peak intensity: {peak_intensity_scs:.4f} inches")
    print(f"  Peak at hour: {peak_hour_scs:.1f} ({peak_position_pct:.0f}% position)")

    # Depth conservation check (10^-6 precision)
    depth_error_scs = abs(total_depth_scs - TOTAL_DEPTH_INCHES)
    print(f"\n  Depth conservation error: {depth_error_scs:.9f} inches")
    print(f"  HMS EQUIVALENCE: {'VERIFIED' if depth_error_scs < 1e-6 else 'FAILED'} (< 10^-6 inch)")

    print(f"\nNote: SCS Type II is the standard design storm for most of CONUS.")
    print(f"      Peak position (~50%) matches TR-55 specifications.")

else:
    print("[!!] ScsTypeStorm not available - install hms-commander")
    print("   pip install hms-commander")
Text Only
2026-01-23 22:10:56 - hms_commander.ScsTypeStorm - INFO - Generated SCS Type II hyetograph: 25 intervals, 17.000000 inches total, peak 7.276 inches
2026-01-23 22:10:56 - hms_commander.ScsTypeStorm - INFO - Generated SCS Type II hyetograph: 25 intervals, 17.000000 inches total, peak 7.276 inches


Generating SCS Type II storm (most common in CONUS)...
  Total depth: 17.0 inches (Atlas 14)
  Duration: 24 hours (HMS constraint)
  Interval: 60 minutes
  Type: II (standard design storm)

[OK] Generated 25 intervals (60-minute)
  Total depth: 17.000000 inches
  Peak intensity: 7.2760 inches
  Peak at hour: 12.0 (50% position)

  Depth conservation error: 0.000000000 inches
  HMS EQUIVALENCE: VERIFIED (< 10^-6 inch)

Note: SCS Type II is the standard design storm for most of CONUS.
      Peak position (~50%) matches TR-55 specifications.
Python
# =============================================================================
# 4.2 Generate All 4 SCS Types
# =============================================================================
if SCS_TYPE_AVAILABLE:
    scs_types = ['I', 'IA', 'II', 'III']
    hyetos_scs = {}

    print("Generating all 4 SCS type storms...")
    print("="*70)
    print(f"{'SCS Type':<12s} {'Region':<25s} {'Peak Hour':>10s} {'Peak (in)':>10s} {'Depth Error':>15s}")
    print("-"*70)

    region_desc = {
        'I': 'Pacific maritime (interior)',
        'IA': 'Coastal Atlantic/Gulf',
        'II': 'Most of CONUS (standard)',
        'III': 'Gulf Coast, Florida'
    }

    for scs_type in scs_types:
        hyeto_type = ScsTypeStorm.generate_hyetograph(
            total_depth_inches=TOTAL_DEPTH_INCHES,
            scs_type=scs_type,
            time_interval_min=60
        )
        hyetos_scs[scs_type] = hyeto_type

        peak_idx = hyeto_type['incremental_depth'].idxmax()
        peak_hour = peak_idx * 1.0
        depth_err = abs(hyeto_type['incremental_depth'].sum() - TOTAL_DEPTH_INCHES)

        print(f"Type {scs_type:<7s} {region_desc[scs_type]:<25s} {peak_hour:>10.1f} {hyeto_type['incremental_depth'].max():>10.4f} {depth_err:>15.9f}")

    print("-"*70)
    print("\n[OK] All 4 SCS types conserve depth at 10^-6 precision")
    print("\nSCS Type Selection Guide:")
    print("  Type I   -> Pacific maritime, inland valleys")
    print("  Type IA  -> Pacific coast, Alaska")
    print("  Type II  -> Standard design storm (most of US)")
    print("  Type III -> Gulf Coast, Florida, intense storms")

    # Visualize all SCS types
    fig, ax = plt.subplots(figsize=(14, 7))

    time_hours_scs = np.arange(len(hyetos_scs['II'])) * 1.0
    colors = ['blue', 'cyan', 'green', 'red']

    for (scs_type, hyeto_type), color in zip(hyetos_scs.items(), colors):
        ax.plot(time_hours_scs, hyeto_type['incremental_depth'], linewidth=2, label=f'Type {scs_type}', color=color, alpha=0.8)

    ax.set_xlabel('Time (hours)', fontsize=12)
    ax.set_ylabel('Incremental Depth (inches)', fontsize=12)
    ax.set_title(f'ScsTypeStorm: All 4 SCS Type Distributions\n{TEST_ARI}-Year, 24-Hour Storm - {TOTAL_DEPTH_INCHES} inches (HMS-Equivalent)', 
                 fontsize=12, fontweight='bold')
    ax.legend(loc='upper right')
    ax.grid(True, alpha=0.3)

    plt.tight_layout()
    plt.show()

    print("\nNote: SCS types are 24-hour ONLY (HMS constraint - cannot be customized).")
Text Only
2026-01-23 22:10:56 - hms_commander.ScsTypeStorm - INFO - Generated SCS Type I hyetograph: 25 intervals, 17.000000 inches total, peak 4.437 inches
2026-01-23 22:10:56 - hms_commander.ScsTypeStorm - INFO - Generated SCS Type I hyetograph: 25 intervals, 17.000000 inches total, peak 4.437 inches
2026-01-23 22:10:56 - hms_commander.ScsTypeStorm - INFO - Generated SCS Type IA hyetograph: 25 intervals, 17.000000 inches total, peak 2.669 inches
2026-01-23 22:10:56 - hms_commander.ScsTypeStorm - INFO - Generated SCS Type IA hyetograph: 25 intervals, 17.000000 inches total, peak 2.669 inches
2026-01-23 22:10:56 - hms_commander.ScsTypeStorm - INFO - Generated SCS Type II hyetograph: 25 intervals, 17.000000 inches total, peak 7.276 inches
2026-01-23 22:10:56 - hms_commander.ScsTypeStorm - INFO - Generated SCS Type II hyetograph: 25 intervals, 17.000000 inches total, peak 7.276 inches
2026-01-23 22:10:56 - hms_commander.ScsTypeStorm - INFO - Generated SCS Type III hyetograph: 25 intervals, 17.000000 inches total, peak 4.250 inches
2026-01-23 22:10:56 - hms_commander.ScsTypeStorm - INFO - Generated SCS Type III hyetograph: 25 intervals, 17.000000 inches total, peak 4.250 inches


Generating all 4 SCS type storms...
======================================================================
SCS Type     Region                     Peak Hour  Peak (in)     Depth Error
----------------------------------------------------------------------
Type I       Pacific maritime (interior)       10.0     4.4370     0.000000000
Type IA      Coastal Atlantic/Gulf            8.0     2.6690     0.000000000
Type II      Most of CONUS (standard)        12.0     7.2760     0.000000000
Type III     Gulf Coast, Florida             12.0     4.2500     0.000000000
----------------------------------------------------------------------

[OK] All 4 SCS types conserve depth at 10^-6 precision

SCS Type Selection Guide:
  Type I   -> Pacific maritime, inland valleys
  Type IA  -> Pacific coast, Alaska
  Type II  -> Standard design storm (most of US)
  Type III -> Gulf Coast, Florida, intense storms

png

Text Only
Note: SCS types are 24-hour ONLY (HMS constraint - cannot be customized).

Part 5: Comprehensive Method Comparison

This section compares all four hyetograph generation methods side-by-side.

Python
# =============================================================================
# 5.1 Depth Conservation Comparison
# =============================================================================
print("="*90)
print("COMPREHENSIVE METHOD COMPARISON")
print("="*90)

comparison_data = []

# StormGenerator
if STORM_GEN_AVAILABLE:
    comparison_data.append({
        'Method': 'StormGenerator',
        'Algorithm': 'Alternating Block',
        'Total Depth (in)': f'{total_depth_ab:.6f}',
        'Depth Error (in)': f'{abs(total_depth_ab - TOTAL_DEPTH_INCHES):.9f}',
        'HMS Equivalent': 'NO',
        'Peak Control': 'Flexible (0-100%)',
        'Durations': 'Any'
    })

# Atlas14Storm
if ATLAS14_AVAILABLE:
    comparison_data.append({
        'Method': 'Atlas14Storm',
        'Algorithm': 'NOAA Temporal Dist.',
        'Total Depth (in)': f'{total_depth_a14:.6f}',
        'Depth Error (in)': f'{abs(total_depth_a14 - TOTAL_DEPTH_INCHES):.9f}',
        'HMS Equivalent': 'YES (10^-6)',
        'Peak Control': 'Fixed (quartile)',
        'Durations': '6h, 12h, 24h, 96h'
    })

# FrequencyStorm
if FREQUENCY_STORM_AVAILABLE:
    comparison_data.append({
        'Method': 'FrequencyStorm',
        'Algorithm': 'TP-40 M3',
        'Total Depth (in)': f'{total_depth_freq:.6f}',
        'Depth Error (in)': f'{abs(total_depth_freq - TOTAL_DEPTH_INCHES):.9f}',
        'HMS Equivalent': 'YES (10^-6)',
        'Peak Control': 'Variable',
        'Durations': '6-48hr'
    })

# ScsTypeStorm
if SCS_TYPE_AVAILABLE:
    comparison_data.append({
        'Method': 'ScsTypeStorm',
        'Algorithm': 'SCS TR-55 Curves',
        'Total Depth (in)': f'{total_depth_scs:.6f}',
        'Depth Error (in)': f'{abs(total_depth_scs - TOTAL_DEPTH_INCHES):.9f}',
        'HMS Equivalent': 'YES (10^-6)',
        'Peak Control': 'Fixed (type)',
        'Durations': '24hr only'
    })

comparison_df = pd.DataFrame(comparison_data)
display(comparison_df)

print("\n" + "="*90)
print("KEY OBSERVATIONS")
print("="*90)
print("\n1. ALL METHODS CONSERVE USER-SPECIFIED DEPTH:")
print("   - All methods now use total_depth_inches as input parameter")
print("   - All methods conserve depth exactly (< 10^-6 inch error)")

print("\n2. HMS-EQUIVALENT METHODS (Atlas14Storm, FrequencyStorm, ScsTypeStorm):")
print("   - Match HEC-HMS output exactly")
print("   - Use official NOAA/SCS temporal distributions")
print("   - Suitable for regulatory submittals")

print("\n3. STORMGENERATOR (Alternating Block):")
print("   - Uses DDF data for temporal pattern only")
print("   - Flexible peak positioning (0-100%)")
print("   - NOT HMS-equivalent (different algorithm)")

print("\n4. DURATION COVERAGE:")
print("   - 6h, 12h, 24h: Atlas14Storm or FrequencyStorm")
print("   - 48h: FrequencyStorm ONLY (fills Atlas14 gap)")
print("   - 96h: Atlas14Storm")
print("   - Any duration: StormGenerator (not HMS-equiv)")
Text Only
==========================================================================================
COMPREHENSIVE METHOD COMPARISON
==========================================================================================
Method Algorithm Total Depth (in) Depth Error (in) HMS Equivalent Peak Control Durations
0 Atlas14Storm NOAA Temporal Dist. 17.000000 0.000000000 YES (10^-6) Fixed (quartile) 6h, 12h, 24h, 96h
1 FrequencyStorm TP-40 M3 17.000000 0.000000000 YES (10^-6) Variable 6-48hr
2 ScsTypeStorm SCS TR-55 Curves 17.000000 0.000000000 YES (10^-6) Fixed (type) 24hr only
Text Only
==========================================================================================
KEY OBSERVATIONS
==========================================================================================

1. ALL METHODS CONSERVE USER-SPECIFIED DEPTH:
   - All methods now use total_depth_inches as input parameter
   - All methods conserve depth exactly (< 10^-6 inch error)

2. HMS-EQUIVALENT METHODS (Atlas14Storm, FrequencyStorm, ScsTypeStorm):
   - Match HEC-HMS output exactly
   - Use official NOAA/SCS temporal distributions
   - Suitable for regulatory submittals

3. STORMGENERATOR (Alternating Block):
   - Uses DDF data for temporal pattern only
   - Flexible peak positioning (0-100%)
   - NOT HMS-equivalent (different algorithm)

4. DURATION COVERAGE:
   - 6h, 12h, 24h: Atlas14Storm or FrequencyStorm
   - 48h: FrequencyStorm ONLY (fills Atlas14 gap)
   - 96h: Atlas14Storm
   - Any duration: StormGenerator (not HMS-equiv)
Python
# =============================================================================
# 5.2 Side-by-Side Visual Comparison (24-hour storms)
# =============================================================================
methods_available = sum([STORM_GEN_AVAILABLE, ATLAS14_AVAILABLE, FREQUENCY_STORM_AVAILABLE, SCS_TYPE_AVAILABLE])

if methods_available >= 2:
    fig, axes = plt.subplots(2, 2, figsize=(16, 12))
    axes = axes.flatten()

    plot_idx = 0

    # StormGenerator
    if STORM_GEN_AVAILABLE:
        ax = axes[plot_idx]
        ax.bar(hyeto_ab['hour'], hyeto_ab['incremental_depth'], width=0.8, alpha=0.7, color='steelblue')
        ax.set_xlabel('Time (hours)')
        ax.set_ylabel('Incremental Depth (inches)')
        ax.set_title('StormGenerator (Alternating Block)\nNOT HMS-Equivalent (~1% tolerance)', fontweight='bold')
        ax.grid(True, alpha=0.3)
        ax.text(0.02, 0.98, f'Total: {total_depth_ab:.4f} in', transform=ax.transAxes, 
                va='top', fontsize=9, bbox=dict(boxstyle='round', facecolor='white', alpha=0.8))
        plot_idx += 1

    # Atlas14Storm
    if ATLAS14_AVAILABLE:
        ax = axes[plot_idx]
        time_hours = hyeto_a14['hour']
        ax.bar(time_hours, hyeto_a14['incremental_depth'], width=0.4, alpha=0.7, color='darkgreen')
        ax.set_xlabel('Time (hours)')
        ax.set_ylabel('Incremental Depth (inches)')
        ax.set_title('Atlas14Storm (NOAA Temporal)\nHMS-Equivalent (10^-6 precision)', fontweight='bold')
        ax.grid(True, alpha=0.3)
        ax.text(0.02, 0.98, f'Total: {total_depth_a14:.6f} in', transform=ax.transAxes, 
                va='top', fontsize=9, bbox=dict(boxstyle='round', facecolor='white', alpha=0.8))
        plot_idx += 1

    # FrequencyStorm
    if FREQUENCY_STORM_AVAILABLE:
        ax = axes[plot_idx]
        time_hours = hyeto_freq['hour']
        ax.bar(time_hours, hyeto_freq['incremental_depth'], width=5/60*0.8, alpha=0.7, color='darkorange')
        ax.set_xlabel('Time (hours)')
        ax.set_ylabel('Incremental Depth (inches)')
        ax.set_title('FrequencyStorm (TP-40)\nHMS-Equivalent (10^-6 precision)', fontweight='bold')
        ax.grid(True, alpha=0.3)
        ax.text(0.02, 0.98, f'Total: {total_depth_freq:.6f} in', transform=ax.transAxes, 
                va='top', fontsize=9, bbox=dict(boxstyle='round', facecolor='white', alpha=0.8))
        plot_idx += 1

    # ScsTypeStorm (Type II)
    if SCS_TYPE_AVAILABLE:
        ax = axes[plot_idx]
        time_hours = hyeto_scs2['hour']
        ax.bar(time_hours, hyeto_scs2['incremental_depth'], width=0.8, alpha=0.7, color='darkred')
        ax.set_xlabel('Time (hours)')
        ax.set_ylabel('Incremental Depth (inches)')
        ax.set_title('ScsTypeStorm (Type II)\nHMS-Equivalent (10^-6 precision)', fontweight='bold')
        ax.grid(True, alpha=0.3)
        ax.text(0.02, 0.98, f'Total: {total_depth_scs:.6f} in', transform=ax.transAxes, 
                va='top', fontsize=9, bbox=dict(boxstyle='round', facecolor='white', alpha=0.8))
        plot_idx += 1

    # Hide unused subplots
    for i in range(plot_idx, 4):
        axes[i].axis('off')

    plt.suptitle(f'{TEST_ARI}-Year, 24-Hour Storm Comparison - Houston, TX ({TOTAL_DEPTH_INCHES} in)', 
                 fontsize=14, fontweight='bold')
    plt.tight_layout()
    plt.show()

png

Python
# =============================================================================
# 5.3 Cumulative Depth Comparison
# =============================================================================
if methods_available >= 2:
    fig, ax = plt.subplots(figsize=(14, 8))

    # StormGenerator
    if STORM_GEN_AVAILABLE:
        ax.plot(hyeto_ab['hour'], hyeto_ab['cumulative_depth'], 'b-', linewidth=2, 
                label='StormGenerator (Exact)', alpha=0.8)

    # Atlas14Storm
    if ATLAS14_AVAILABLE:
        ax.plot(hyeto_a14['hour'], hyeto_a14['cumulative_depth'], 'g--', linewidth=2, 
                label='Atlas14Storm (HMS-equiv)', alpha=0.8)

    # FrequencyStorm
    if FREQUENCY_STORM_AVAILABLE:
        ax.plot(hyeto_freq['hour'], hyeto_freq['cumulative_depth'], 'orange', linewidth=2, linestyle='-.', 
                label='FrequencyStorm (HMS-equiv)', alpha=0.8)

    # ScsTypeStorm
    if SCS_TYPE_AVAILABLE:
        ax.plot(hyeto_scs2['hour'], hyeto_scs2['cumulative_depth'], 'r:', linewidth=2, 
                label='ScsTypeStorm Type II (HMS-equiv)', alpha=0.8)

    # Target line
    ax.axhline(TOTAL_DEPTH_INCHES, color='black', linestyle='--', linewidth=1.5, 
               label=f'Atlas 14 Target: {TOTAL_DEPTH_INCHES} in')

    ax.set_xlabel('Time (hours)', fontsize=12)
    ax.set_ylabel('Cumulative Depth (inches)', fontsize=12)
    ax.set_title(f'Cumulative Depth Comparison - All Methods\n{TEST_ARI}-Year, 24-Hour Storm - Houston, TX', 
                 fontsize=13, fontweight='bold')
    ax.legend(loc='lower right', fontsize=10)
    ax.grid(True, alpha=0.3)

    plt.tight_layout()
    plt.show()

    print(f"\nAll methods now conserve the user-specified depth exactly (< 10^-6 inch error).")
    print(f"All curves converge to {TOTAL_DEPTH_INCHES} inches at 24 hours.")

png

Text Only
All methods now conserve the user-specified depth exactly (< 10^-6 inch error).
All curves converge to 17.0 inches at 24 hours.

Part 6: Spatial Tools Overview (Atlas14Grid + Atlas14Variance)

In addition to hyetograph generation, ras-commander provides spatial precipitation tools:

Atlas14Grid

  • Purpose: Access gridded PFE (Precipitation Frequency Estimates) values
  • Data Source: NOAA CONUS NetCDF via HTTP range requests (99.9% data reduction)
  • Coverage: CONUS (24N-50N, -125W to -66W)
  • Use Case: Spatially variable rainfall, distributed precipitation

Atlas14Variance

  • Purpose: Assess whether uniform rainfall is appropriate
  • Input: HEC-RAS geometry HDF file (extracts project extent)
  • Output: Min/max/mean/range statistics for precipitation
  • Decision Support: Range > 10% suggests spatially variable rainfall needed

Example Usage

Python
from ras_commander.precip import Atlas14Grid, Atlas14Variance

# Quick variance check (100-yr, 24-hr)
stats = Atlas14Variance.analyze_quick("MyProject.g01.hdf")

if stats['range_pct'] > 10:
    print("Consider spatially variable rainfall")
else:
    print("Uniform rainfall appropriate")

Complete Demonstration: See examples/725_atlas14_spatial_variance.ipynb

Conclusion

This notebook demonstrated all six precipitation tools available in ras-commander.

Summary Table

Method Algorithm HMS Equiv Depth Conservation Durations Use Case
StormGenerator Alternating Block NO Exact Any Flexible peak positioning
Atlas14Storm NOAA temporal dist YES 10^-6 6h, 12h, 24h, 96h Modern Atlas 14, regulatory
FrequencyStorm TP-40 M3 YES 10^-6 6-48hr Houston area, TP-40 legacy data, 48h gap fill
ScsTypeStorm SCS TR-55 curves YES 10^-6 24hr only SCS Type I/IA/II/III
Atlas14Grid NOAA CONUS NetCDF N/A Byte-exact N/A Spatially distributed PFE
Atlas14Variance Statistical N/A N/A N/A Uniform vs distributed decision

Method Selection Decision Tree

Text Only
Need HMS-equivalent results? (regulatory, HMS-RAS coordination)
|
+-- Modern Atlas 14 (6h, 12h, 24h, 96h)?
|   +-- Use Atlas14Storm
|
+-- TP-40 or need 48hr duration?
|   +-- Use FrequencyStorm
|
+-- SCS Type I, IA, II, or III (24hr)?
    +-- Use ScsTypeStorm

Need flexible peak positioning (0-100%)?
+-- Use StormGenerator (NOT HMS-equivalent)

Need spatially distributed PFE?
+-- Use Atlas14Grid + Atlas14Variance

Key API Change

All methods now use total_depth_inches as an input parameter:

Python
# StormGenerator (Alternating Block)
hyeto = gen.generate_hyetograph(
    total_depth_inches=17.0,  # User-specified depth
    duration_hours=24,
    position_percent=50
)

# Atlas14Storm (HMS-equivalent)
hyeto = Atlas14Storm.generate_hyetograph(
    total_depth_inches=17.0,
    state="tx", region=3,
    aep_percent=1.0
)

Known Limitations

Limitation Workaround
48h Atlas14Storm not available Use FrequencyStorm (HMS-equivalent)
SCS types are 24hr only HMS constraint - cannot be changed
StormGenerator not HMS-equivalent Use HMS-validated methods for regulatory work
  • 721_precipitation_hyetograph_comparison.ipynb - Precipitation hyetograph comparison workflow
  • 722_atlas14_multi_project.ipynb - Batch processing multiple projects
  • 725_atlas14_spatial_variance.ipynb - Spatial variance analysis
  • 900_aorc_precipitation.ipynb - AORC historic precipitation

References

  • Chow, V.T., Maidment, D.R., Mays, L.W. (1988). Applied Hydrology. McGraw-Hill. Section 14.4
  • NOAA Atlas 14: https://hdsc.nws.noaa.gov/pfds/
  • NOAA Temporal Distributions: https://hdsc.nws.noaa.gov/pub/hdsc/data/
  • HEC-HMS Technical Reference Manual: Frequency Storm methodology
  • NRCS TR-55: SCS Type distributions
  • HCFCD M3 Models: Harris County Flood Control District methodologies
CLB Engineering Corporation  ·  LLM Forward Engineering
RAS Commander is a free and open-source project maintained by CLB Engineering Corporation. For agencies and firms seeking to modernize H&H workflows with LLM Forward approaches, contact CLB to partner with the engineers who wrote the automation.