Abstract:
The main objective of this study is to identify the main causes and effects of flooding and drainage
problems on agricultural production of Lake Tana surrounding plains, mainly on Fogera, Dembia and
Kunzila floodplains. The paper intends to answer 1) variability of runoff and rainfall data in identify the
cause of2006 flooding on LT shores 2) the best-fit flood analysis distribution function for major rivers 3)
The socio economic impact of flooding on agricultural production and 4) potential mitigation measures
that reduces adverse effect of flood and drainage problems.
The rainfall variability analysis of LT basin in 2006 was shows that on average 43% increase-in wet
season rainfall than the normal (mean). All rainfall gauging stations shows an increase in rainfall in 2006.
Similarly the variability analysis of major rivers was also shows that, on average 35% increase in flood
season stream flow of G/Abbay, Gumara, Ribb, Megech and Koga. The trend of these rivers shows that
maximum runoff for the year 2006 was higher than the mean of the long term maximum flood. Whereas
Lake Tana maxi mum flood level of 2006 (1787. l 55masl) show an increase by 16 cm only from the mean
flood levels of pervious records ( 1787 masl). Therefore LT backwater effect in 2006 was less and it
doesn't have much contribution for 2006 flooding. Flood frequency analysis of major rivers were done and it is found that Extreme Value Type One
maximum likelihood probability distribution is best fit for G/Abbay and Koga rivers. Pearson III method
of moment probability distribution is a best fit for Megetch and Ribb rivers. For Gumara river Pearson III
probability weighted moment distribution better estimate flood quantiles with less standard error. It is also
found that Gamma two probability weighted moment is best fit for Lake Tana water surface level. In
general from rainfall and flood frequency analysis 2006 year flooding may have a chance to occur once in
six years in L TB.
The 2006 year flood damage indicates that there is high impact on agricultural production of Lake Tana
surrounding plains. 107,647 peoples were actually affected by flood. At least 448, 91 0 quintal of food
grain, 1230 domestic animals, 9634 chickens and 1088 bee-hives were damaged by 2006 flood. The
