No abstract

In the middle reaches of the Asahi River, gravel bars were disappeared and were mostly covered by vegetation on the bars in the recent years. At a sand bar of the Gion area which is one of the fairly vegetated bars, gravel bar restoration work was carried out by removal of vegetation and deposited sand in 2005. After that the gravel bar have been maintained there in several years, and aggradation of severely scoured riverbed at low-water channel was confirmed. Numerical simulation using a vegetation growth and disappearance model proves that the conducted gravel bar restoration work have an effect on an expansion of gravel bar and river bed aggradation at local scour area. Furthermore, an expansion of spawning area of ayu by gravel bar restoration was clarified quantitatively using PHABSIM assessment.

Incarcerated groin hernia is a common surgical emergency. However, reports of incarcerated femoral hernia treated with elective totally extraperitoneal repair are extremely rare. A 62-year-old woman visited our hospital with lower abdominal pain and bulging from a right groin lesion. The patient was diagnosed as having right incarcerated femoral hernia containing greater omentum by computed tomography. As there were no clear findings of intestinal obstruction and peritonitis, elective surgery was performed. Intraoperatively, the hernia sac had herniated into the right femoral canal. We could release the hernia sac using laparoscopic forceps. After reduction of the hernia sac, polypropylene mesh was placed in the preperitoneal space and fixed to Cooper’s ligament. The patient’s postoperative course was uneventful, and she was discharged 3 days after surgery. We consider elective totally extraperitoneal repair for incarcerated femoral hernia to be an effective procedure for selected patients who have been diagnosed accurately.

As one of flood control measures, installation of a fixed weir is scheduled at the bifurcation point between the Asahi River and its distributary, the Hyakken River. Forestation has recently been of concern in these rivers, because it might cause a change of diverging discharge at the weir. Therefore, it is necessary to clarify the effect of vegetation on distributary for river management. This study describes flow simulations for two floods of different scales in these rivers, and demonstrates the relation between vegetation conditions, longitudinal variation of water levels and diverging discharges. Results showed that vegetation growth contributes little to increase of water levels because these rivers were mostly covered by trees whose heights were taller than water levels during these floods. Additionally, simulated water levels are approximately consistent with observations, except for situations when the Asahi River discharges were recorded at less than 2000 m 3 /s. Such discrepancy is supposedly attributable to low accuracy of the rating curve.

非会員 岡山大学環境理工学部 環境デザイン工学科（同上）Forestation in rivers generally causes reduction of river flow capacity. Therefore, we have to manage a vegetation condition in the river properly. The object of this study is to forecast the vegetation condition with enough accuracy for effective management tasks. We had conducted a field observations of an annual vegetation growth rate, hydraulic conditions of wash out and lodging of vegetation, and bed deformation at Ohara area in the Asahi River from 2008 to 2013. Then, we developed a vegetation dynamic model based on the field observations. We simulated the vegetation condition at Ohara area in 2013 by using this model, and also examined the model by comparing the simulation results with an aerial photograph taken at Ohara area. The simulation results showed that the model can basically reproduce vegetation condition in Ohara area.