ARISTOTLE UNIVERSITY OF THESSALONIKI FACULTY OF FORESTRY AND NATURAL ENVIRONMENT Institute of Mountainous Water Management and Control

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1 ARISTOTLE UNIVERSITY OF THESSALONIKI FACULTY OF FORESTRY AND NATURAL ENVIRONMENT Institute of Mountainous Water Management and Control Torrent Basin, Mountainous Watershed Management Dr. Panagiotis Stefanidis Associate Professor and Chairman Dr. Ioannis A. Kalinderis Research Assistant Drainage Basin Drainage Basin is the area of land that drains water, sediment, and dissolved materials to a common outlet. (FISWRG 1998) The delimitation of the drainage basin is done with the topographic divide. The topographic divide between two watersheds is relatively easy to locate in mountainous regions, but is extremely difficult to determine in areas that are flat or have uniform relief. 2

Kalinderis Research Assistant Drainage Basin Drainage Basin is the area of land that drains water, sediment, and dissolved materials to a common outlet.

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3 Watershed Delineation There are two basic steps to follow in watershed delineation. Step 1: Choose the point of the watershed outlet. This is generally our point of interest for designing a structure or monitoring location. Step 2: Delineate the watershed boundary by drawing perpendicular lines across the elevation contour lines for land that drains to the point p of interest. Note - There are a few things to remember when you are working with topographic maps. A watershed boundary always runs perpendicular to the contour lines. Arrows that point upstream are valleys. Arrows that point downstream are hills. 5 6

Step 2: Delineate the watershed boundary by drawing perpendicular lines across the elevation contour lines for land that drains to the point p of interest.

4 Topographic Divide 7

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9 17 Empirical and Analytical formulas WATER DISCHARGE 18

10 Maximum discharge of runoff in watersheds The estimation of the maximum discharge (Q max100 ) on mountainous watersheds, is often a problem due to the lack of data. As a result the estimation is based on indirect methods (empirical, stochastic and analytical equations). Through these methods the estimation of the discharge is done using data that are easily accessible (Basin Area, Average annual depth h of precipitation, etc). 19 Empirical, Stochastic equations q: Discharge per km 2 (m 3 /s, km 2 ), Q = q A (m( 3 /s) Valentini q 30 = A max 1 2 Hoffbauer A > 10 Km 2 max 1 Semi - Mountainous areas a = 0,35 ~ 0,50 A 2 Mountainous areas a = 0,50 ~ 0,70 40 qmax = a 1 Melli ( 100A F< ) 150 Km 2 6, a = 0,4 Melli q 60 = a 20

Through these methods the estimation of the discharge is done using data that are easily accessible (Basin Area, Average annual depth h of precipitation, etc).

11 32 qmax = a Kresnik 1 0,5 + A 2 a = 0,6 ~ 2,0 Kresnik Müller 40 A1 y1+ A2 y2 qmax = y m, ym = 1 A 3 A A 1 Forested Area A 2 Agricultural Area y 1, y 2 Runoff Coefficients Area Land Cover Small Terrain Gradient Average Steep Alpine areas Grasslands 0,4 0,6 0,8 Semi Mountainous Forested Areas 0,2 0,4 0,6 Low lands Agricultural Areas 0,1 0,2 0,4 21 Analytical formulas The most important analytical formulas used in Watershed Management in Greece are the equations of: Turazza Giandotti 22

Grasslands 0,4 0,6 0,8 Semi Mountainous Forested Areas 0,2 0,4 0,6 Low lands Agricultural Areas 0,1 0,2 0,4 21 Analytical

12 Q Turazza max(100) hp = 11,57 a K F t + t p c όπου, a: συντελεστής απορροής (εκτιμάται) Κ: συντελεστής αιχμής, Κ=2 t p: η διάρκεια της βροχής σε ημέρες. Θεωρείται ότι t p=t c t c: μέγιστος χρόνος συγκέντρωσης της απορροής (ημέρες) t' c tc =, όπου t c ο χρόνος t c εκφρασμένος σε ώρες 24 4 F + 1,5 L t' c = (ώρες) 0,8 Z L: Μήκος κεντρικής κοίτης (Km) Z: διαφορά μεταξύ μέσου και ελάχιστου υψομέτρου (m) h p: μέγιστο ύψος βροχής με διάρκεια ίση με t p (m) h' h p = 1000 h : ύψος βροχής με διάρκεια t p (mm) a h' = [a ( t' p )] t' p 72 a: συντελεστής που προσδιορίζεται από τον τύπο h a = 3,27 t p: ο χρόνος t p σε ώρες h: Μέγιστο ύψος βροχής 24/ώρου 23 όπου P: ύψος βροχής σε χρόνο t c (mm) Q max Giandotti 0,277 P F = t c t' c P = h 24 h: μέγιστο ύψος βροχής 24/ώρου (mm) t c: μέγιστος χρόνος συγκέντρωσης της απορροής 4 F + 1,5 L t' c = (ώρες) 0,8 Z L: μήκος κεντρικής κοίτης (Km) Ζ: διαφορά μεταξύ μέσου και ελάχιστου υψομέτρου (m) 24

διαφορά μεταξύ μέσου και ελάχιστου υψομέτρου (m) h p: μέγιστο ύψος βροχής με διάρκεια ίση με t p (m) h' h p = 1000 h : ύψος βροχής με διάρκεια t p (mm) a h' = [a ( t' p )] t' p 72 a: συντελεστής που

13 Stiny Herheulidze Formula ESTIMATION OF SEDIMENT DISCHARGE 25 The transportation of sediments within the area of mountainous watersheds is one of the most important torrential characteristic. It is described by three stages: 1. Production of sediments caused by the torrential phenomena on the basin area, 2. Transportation of sediments by water,, through the drainage network and 3. Deposit of sediments on the plain areas. 26

14 Sediment Discharge formula of Stiny Herheulidze A empirical equation stated by the Austrian Stiny and revised by the Russian Herheulidze. It provides satisfactory results and it s s widely spread in the Watershed Management practice. Pn m G= Q, Y (100 P ) Όπου Q: Water Discharge (m³/sec) n n 3 (m /s) P n : Coefficient regarding the gradient of the basin m: torrential rate of the basin Y n : Relative density of transported sediments (tn) 27 Thank you for your attention!!! 28

Pn m G= Q, Y (100 P ) Όπου Q: Water Discharge (m³/sec) n n 3 (m /s) P n : Coefficient regarding the gradient of the

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