Taşkın akımlarının tahmininde WRF-ARW ve HEC-HMS modellerinin birlikte kullanılması, Ergene Havzası örneği
Prediction of flood runoff by coupling wrf-arw and  HEC-HMS models, Ergene Basin
Yazar: FATMA BETÜL DEMİR
Danışman: PROF. DR. SEVİNÇ ASİLHAN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Meteoroloji Mühendisliği Ana Bilim Dalı / Atmosfer Bilimleri Bilim Dalı
Derece: Yüksek Lisans, 2019
Konu: Meteoroloji = Meteorology

Özet:
Taşkınlar şiddetli yağışlar, kar erimeleri ve zeminin doyması ile birlikte akarsuyun yatağından taşarak çevresine yayılması sonucu oluşan ve büyük ölçüde ekonomik, sosyal, çevresel ve tarımsal zararlara neden olan doğal bir afettir. Son yıllarda nüfus artışı ile birlikte ekolojik dengenin bozulması ve iklim değişikliğinin de etkisi ile taşkın olayları dünya çapında artış göstermekte ve daha da yıkıcı bir hal almaktadır. Taşkınların meydana getirdiği zararları azaltmak için taşkın tahmini çok önemlidir. Taşkınların tahmini ve erken uyarı sistemlerinin geliştirilmesi oluşabilecek can ve mal kayıplarının büyük ölçüde önüne geçilmesini sağlamaktadır. Güvenilir bir taşkın erken uyarı sisteminin hidrolojik olduğu kadar meteorolojik bilgileri içermesi de gerekmektedir. Bu nedenle meteorolojik ve hidrolojik modellerin bir arada kullanılması erken uyarı için daha güvenilir sonuçlar sağlayacaktır.
Bu çalışmada, Ergene Havzasında yer alan Kırklareli iline bağlı Pehlivanköy ilçesinde 15 Şubat 2010 tarihinde meydana gelen taşkını oluşturan akım (debi) miktarını belirlemede meteorolojik ve hidrolojik modellerin birlikte kullanımının taşkın tahminlerindeki performansları incelenmiştir. Meteorolojik model için orta ölçekli sayısal hava tahmin modeli olan Weather Research and Forecasting (WRF) modeli ile hidrolojik bir yağış-akış modeli olan HEC-HMS modeli birlikte kullanılarak taşkın tahmininde bu iki modelin performansı incelenmiştir. 
Öncelikle WRF-ARW modeli 7 farklı mikrofizik seçeneği için çalıştırılmıştır. Daha sonra WRF-ARW yağış çıktılarından OMGİ'lere en yakın konumlara ait yağış verileri elde edilmiştir. WRF-ARW modelinden elde edilen yağışlar ile OMGİ'lere ait veriler karşılaştırıldığında 7.  mikrofizik seçeneği olan Goddord seçeneğinin gözlem verileri ile daha uyumlu olduğu belirlenmiştir. Bu nedenle Goddord mikrofizik seçeneğine ait yağış değerleri HEC-HMS modelinde kullanılmıştır.
HEC-HMS modeli öncelikle OMGİ yağış verileri ile kalibre edilmiş, daha sonra WRF-ARW yağış çıktıları ve kalibre edilmiş değerler ile model tekrar çalıştırılmıştır. Model İnanlı ve Lüleburgaz AGİ' leri için akım tahmini yapacak şekilde çalıştırılmıştır. Kalibrasyon sonucunda model Lüleburgaz istasyonu için gözlem verileri ile uyumlu bir yol izlemiş en yüksek akım miktarını aynı gün içerisinde 58 m3/s daha fazla tahmin etmiştir. WRF-ARW yağış çıktıları modein tekrar çalıştrılması işleminde ise model İnanlı istasyonu için en yüksek akım miktarını gözlenmiş veriye göre 1 gün gecikme ile 14 m3/s daha az tahmin etmiştir.

Abstract:
Flood is the most devastating economically weather phenomenon and natural hazard. The rapid and sudden increase in the amount of water in a river / stream bed and the destruction of living beings, land and property around the bed is called flood. This increase occurs in a way of falling more precipitation than normal or melting of existing snow covers. In recent years, with the effects of climate change flood events getting increased day by day worldwide as well as in Turkey. While climate change brings about drought on some areas, on the other areas it causes heavy rainfall which cause flood. In addition to climate change, with growing population, industrilization and urbanization also contribute to increse of flood events because of the inreasing of impervious areas.  Therefore, the flood studies, in particular mesoscale models studies, become crucial to predict formation of flood and reduce it' s negative effects by taking precautions.
Floods are directly affected by rainfall. So, floods become a devastating disaster due to urbanization and infrastructure problems. Flow estimation which could occur in any heavy rainfall situtaion is significantly important to reduce damages and prevent loss of life. Weather prediction is one of most important component of flow estimation and essential to develop flood warning system. The increase in the capacity of meteorological and hydrological models as well as the use of data obtained through satellites have increased the reliability of flood forecasts in recent years. Numerical weather forecasting models are important for the success of estimating the lag time. Recently, significant improvements have been made in the development of models used forecasting. One of these developments is Weather Research Forecasting (WRF) produced by NCAR. WRF is a next-generation mesoscale numerical weather prediction system designed for both atmospheric research and operational forecasting applications. In addition HEC-HMS is a rainfall-runoff model which is designed to simulate the complete hydrologic processes of dendritic watershed systems and it convert the rainfall to runoff.
In this study, the performances of meteorological and hydrological models in the flood estimation were investigated in determining the amount of flow for the flood occurring in the district of Pehlivanköy in the Kirklareli province of Ergene Basin on February 15, 2010. For the meteorological model the Weather Research and Forecasting (WRF) model, which is a mid-sized numerical weather forecasting model, and HEC-HMS model, which is a hydrologİcal rainfall-runoff model, were used together to evaluate the performance of these two models in flood prediction. WRF-ARW outputs were used input precipitation data for HEC-HMS model.
In present study, firstly analysis of precipitation and discharge values are made. Annual seasonal averages were analyzed for two variable. Also for the ptrecipitation, annual maximum precipitation values were analyzed. Analyzing of discharge values belonging to 5 flow observed stations (AGİ) shows that most discharge values are measured in winter while most precipitation falls in winter and autumn. Besides annual maximum precipitation graphs show that maximum precipitation values are in increasing trend except for Uzunköprü OMGİ.
In other part of the analyzing of data, flood frequency analysis were made for 7 AGİ. According to the calculated values, the highest flow between 1988 and 2006 was 800 m3/s at the Lüleburgaz station on the Ergene River. According to the analysis, it is interpreted that a current with this size can be seen again within 21 years or with a probability of  0.05. Likewise, it is expected that currents of 280 m3/s at İnanlı station, 14.6 m3/s at Soğucak station, 113 m3/s at Poyralı station and 28 m3/s at Kocahıdır station will occur within 21 years.
First, the WRF-ARW model was run for 10-18 February 2010 to get the values belonging flood period with 2 domain. When running WRF-ARW 7 different microphysic option were used. Then, rainfall data from the WRF-ARW outputs closest to OMGIs locations were obtained. When the data obtained from the WRF-ARW model and the data from the OMGIs were compared, it was determined that the Goddord option which is the 7th micro-physics option was more compatible with the observation data. Therefore, precipitation values of Goddord microphysics were used in the HEC-HMS model.
The HEC-HMS model was first calibrated with observed precipitation data of Kırklareli, Lüleburgaz and Çorlu OMGIs and then HEC-HMS model was run again to predict flow for case date with precipitation data obtained from WRF-ARW, The model was run to estimate the discharge for Luleburgaz AGİ and İnanlı AGİ. Precipition values was interpolated over the basin with Inverse Distance Method (IDW) which takes place in meteorologic model in HEC-HMS. As a result of the calibration, the model has followed a path consistent with the observation data for the Lüleburgaz station and estimated the highest discharge 288 m3/s when observed value is 230 m3/s on the same day. In process of running with WRF-ARW precipitation outputs (re-run), the model estimated the highest discharge amount for the station with less than 14 m3 / s with 1 day delay compared to the observed data.
When compare the calibration and re-run results it is seen that discharge prediction from HEC-HMS and observed discharge values are not coincide except for Lüleburgaz AGI in calibration process. For this study it is conclueded that these differences between model and observed discharge is due to the difference in precipitation value. The precipitation values belonging to OMGİ and WRF-ARW output shows differences in time interval of 1 day. For example; The data observed on February 13 showed a precipitation of 21.7 mm while this value was 5.2 mm for WRF-ARW outputs.
As a result of this study, it is conlueded that HEC-HMS is directly affected by precipitation so, precipitation estimates should do carefully even WRF-ARW and HEC-HMS model can be used together for prediction discharge. 

Increasing the number of flood events caused by climate change, improper industrialization and urbanization increase the flood damages caused by the disturbances in the land of human origin. Therefore, the risk of flooding should be taken into consideration when planning the city. In addition, the development of flood early warning systems is also important in order to prevent flood damage. Therefore, hydrological and meteorological models should be developed by considering basin characteristics and used in early warning systems. With this and similar studies to be applied to all basins in our country, model parameters can be determined according to the basin characteristics and thus can help to develop early warning systems.