Figure: 30 TAC §299.15(a)(1)(A)

HYDROLOGIC CRITERIA FOR DAMS | ||

Classification | ||

Hazard, as defined in §299.14 of this title (relating to Hazard Classification Criteria) |
Size, as defined in §299.13 of this title (relating to Size Classification Criteria) |
Minimum Design Flood Hydrograph (expressed as a percentage of the probable maximum flood (PMF)). |
---|---|---|

Low | Small | 25% PMF |

Intermediate | 25% PMF to 50% PMF | |

Large | 50% to 75% PMF | |

Significant | Small | 50% PMF |

Intermediate | 50% PMF to 75% PMF | |

Large | 75% to PMF | |

High | Small | 75% PMF |

Intermediate | 75% to PMF | |

Large | PMF | |

When a range is given, the minimum flood hydrograph must be determined by straight-line interpolation within the given range. Interpolation must be based on either height of dam or maximum storage capacity, whichever results in the highest percentage of PMF. The interpolation for large, low-hazard dams for height must be between end points of 100 feet and 50% PMF and 200 feet and 75% PMF. The interpolation for large, low-hazard dams for maximum storage capacity must be between the end points of 50,000 acre-feet and 50% PMF and 300,000 acre-feet and 75% PMF. The interpolation for large, significant-hazard dams for height must be between end points of 100 feet and 75% PMF and 200 feet and PMF. The interpolation for large, significant-hazard for maximum storage capacity must be between the end points of 50,000 acre-feet and 75% PMF and 300,000 acre-feet and PMF. |