Prof.T.Shivaji Rao, Director,Center for environmental studies, Gitam University, Visakhapatnam | Prof.M.Ramesh, Head of the Department of Civil Engineering, Gitam University,Visakhapatnam, |
To understand basics of backwater curves caused by dams across the rivers see the following website:
Satara,sangli and Kolhapur Districts are bound to get flooded by increased Alamatti Dam. Why?http://www.indianetzone.com/46/geography_satara_district.htm
WHY KARNATAKA STATE IS HELPLESS IN PREVENTING FLOODING OF SANGLI DISTRICT
Irrigation experts told Frontline that both States, especially Maharashtra (by virtue of being the upper riparian), probably stored waters in their dams far in excess of the necessary storage level before the onset of the monsoon. They probably did not wait to build up storage levels slowly as the monsoon progressed fearing the level would come down if the monsoon failed. But with excess rains in the catchment areas in Maharashtra, the States were forced to release water from their dams, which had reached their full reservoir levels (FRLs) thereby aggravating the flood situation.
Even as the people are reeling under the impact of the floods, Maharashtra and Karnataka indulged in a dispute over the release of the Krishna waters. Maharashtra has accused Karnataka of not fulfilling its obligation to release adequate quantities of the Krishna waters from the Almatti dam so that the flood situation and the backwater effect in its inundated southern districts could be brought under control. It even got Prime Minister Manmohan Singh to intervene in the matter.
Karnataka has refused to release 6 lakh cusecs of water from the Almatti dam that Maharashtra has been demanding. On August 5, Karnataka released 4.20 lakh cu against an inflow of 3.57 lakh cu, reducing the water level in the dam to 516.4 metres, as against the FRL of 519.6 m.
Karnataka Chief Minster N. Dharam Singh said the release of 6 lakh cu would inundate 600 villages in Karnataka. But with Maharashtra increasing the outflow from its upstream Koyna dam (3.96 lakh cu was released on August 6) steadily, Karnataka, according to engineers at the Almatti dam site, will also have to increase gradually the outflow to 5 lakh cu. The water discharges from the Almatti dam have already affected over 60 villages in Hungund and Muddebihal taluks of Bagalkot and Bijapur districts.
According to the Water Resources Minister M. Mallikarjun Kharge, Maharashtra was needlessly creating a controversy over the discharge of water from Almatti. His contention is that the villages in Sangli and Kolhapur could not have been affected by the backwaters of the Almatti as they are located at a height of 538 metres above sea level. After all, floods had ravaged villages in both districts in 1964 and 1976, before the dam was constructed. He also claimed that in 2002-03 and 2004, when the dam had reached full storage level, no village in Maharashtra was submerged. Irrigation experts also point out that a joint survey by engineers from both States, which was later cleared by the Central Water Commission (CWC), stated that villages upstream up to and beyond Sangli would not be flooded even when the water level at the Almatti dam reached 524.256 m..See the following article on "DEVASTATION AND DISPUTE" in FRONTLINE MAGAZINE,Chennai
KARNATATAKA MINISTER,KHARGE IS MISLEADING ON FLOODING OF SANGLI, KOLHAPUR AND SATARA REGIONS
The variation in relief ranges from the pinnacles and high plateaus of the main Sahyadari range having a height over 4500 feet above mean sea level to the subdued basin of the Nira river in Phaltan tahasil, with an average height of about 1700 feet above mean sea level.
http://www.indianetzone.com/46/geography_satara_district.htmhttp://tshivajirao.blogspot.com/2011/01/almathi-dam-hazardous.html
https://sites.google.com/site/ayyagaribhujangarao/backwateraffluxtheory
Roughness Coefficients (Manning’s “n”) for Overland Flow
| Surface Description | n |
| Dense Growth | 0.4 - 0.5 |
| Pasture | 0.3 - 0.4 |
| Lawns | 0.2 - 0.3 |
| Bluegrass Sod | 0.2 - 0.5 |
| Short Grass Prairie | 0.1 - 0.2 |
| Sparse Vegetation | 0.05 - 0.1 |
| Bare Clay-Loam Soil (eroded) | 0.01 - 0.0 |
| Concrete/Asphalt - very shallow depths (less than ¼ inch) - small depths (1/4 inch to several inches) | 0.10 - 0.1 0.05 - 0.1 |
| Roughness Coefficients (Manning’s “n”) for Channel and Pipe Flow | |
| Reach Description | n |
| Natural stream, clean, straight, no rifts or pools | 0.03 |
| Natural stream, clean, winding, some pools or shoals | 0.04 |
| Natural stream, winding, pools, shoals, stoney with some weeds | 0.05 |
| Natural stream, sluggish deep pools and weeds | 0.07 |
| Natural stream or swale, very weedy or with timber underbrush | 0.10 |
| Concrete pipe, culvert or channel | 0.013 |
| Corrugated metal pipe | 0.012 – 0.024* |
| Spiral rib metal pipe | 0.012 |
| Corrugated polyethylene pipe | 0.020 |
| Smooth-lined corrugated polyethylene pipe | 0.012 |
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