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# Table 2 Formula for computation of morphometric parameters

From: Flood risk analysis: causes and landscape based mitigation strategies in Dire Dawa city, Ethiopia

No | Morphometric Parameters | Formula/ definitions/methods | References |
---|---|---|---|

Linear aspect | |||

1 | Stream order | Hierarchical order | Strahler 1964a, b |

2 | Stream Length (Lu) | Length of the Stream (km) | Horton 1945 |

3 | Mean Stream Length (Lsm) | Lsm = Lu / Nu, Where, Lu = Total Stream length of order ‘U’, Nu = Stream length of next higher stream order. | Horton 1945 |

4 | Stream length Ratio(Rl) | Rl = Lu/Lu-1; where, Lu = Total number of stream segment of order ‘U’, Lu-1 = Stream length of next lower order | Horton 1945 |

5 | Bifurcation Ratio (Rb) |
Rb = Nu / Nu+ 1 Where, Nu = Total Number of stream segments of order ‘U’ Nu+ 1 = Number of segments of the next higher order. | Schumm 1956 |

Areal aspect | |||

6 | Drainage Density (Dd) | Dd = L/A Where, L = Total length of Stream, A = Area of the Watershed | Horton 1945 |

7 | Stream Frequency (Fs) | Fs = N /A. Where, N = Total number of Stream, A = Area of the Watershed. | Horton 1945 |

8 | Texture ratio (T) | T = N1/P. Where N1 = Total number of first order stream, p = perimeter of watershed | Horton 1945 |

9 | Form Factor (Rf) | Rf = A / (Lb) 2. Where, A = Area of the Watershed, Lb = Maximum Basin length. | Horton 1932 |

10 | Circularity Ratio (Rc) | Rc = 4ðA/ P2. Where, A = Area of the Watershed, P = Perimeter of the basin, Ð = 3.14 | Strahler 1964a, b |

11 | Elongation Ratio (Re) | Re = 2√ (A/ð) / Lb. Where, A = Area of the Watershed, Lb = Maximum Basin length, Ð = 3.14. | Schumm 1956 |