In order to reduce flooding, communities often try to control runoff with a storm sewer network, detention basins, low impact developments, and upstream storage to reduce stream overflow. Numerical models can help predict the effect these strategies will have before expensive construction projects are underway. A coupled 1D/2D hydraulic model using XPSWMM was created for the town of Kalona, IA, to test different strategies for flood reduction. XPSWMM utilizes one dimensional and two dimensional St. Venant equations to model flow in streams and pipes, or overland flow on the surface, respectively. The town of Kalona, upstream highlands, and the downstream floodplains were modeled utilizing a 4 meter cell-size unstructured grid. The model was neither calibrated nor validated, but its performance was comparable to a previously built MIKE 11/21 model of the same area when given the same inputs. The city drains into Salvesen Creek, the Central Drainage Ditch, and the East Drainage Ditch, with Salvesen Creek having the largest drainage area. 14 agricultural detention ponds upstream of the town were modeled to determine their effectiveness in reducing stream overflow, while modifications to the storm sewer network and in situ detention provided relief from local runoff. The detention ponds and modifications were modeled both separately and together and compared to a base model using the 10 year, 25 year, 50 year, 100 year, and 500 year, 3 hour storms. The different methods were compared using three index points: City Hall, Pleasant View Circle, and in a softball practice area. The upstream agricultural detention ponds provided a peak reduction of 2%, 13%, and 9%, respectively, while the in situ modifications reduced flooding by 0%, 44%, and 18%, respectively, for the 10 year storm. The combined techniques reduced flooding by 2%, 44%, and 20%, respectively. During the 100 year storm, the detention ponds, modifications, and combined techniques reduced peak flood depths by 17%, 24%, and 14%; 2%, 3%, and 22%; and 17%, 55%, and 23%, respectively. This demonstrated that the in situ modifications were more effective during low flood events while ponds were more effective at high flood events. The combined approach was most effective when the two methods complemented each other. Future work might determine areas throughout the town where reduced flow and in situ modifications together would be most effective and design approaches to maximize flood reduction. Additional features to be modeled include pumps to increase capacity in the storm sewer network, levees, and supplementary drainage channels.

Hydroplaning is a major concern on high speed roadways during heavy rainfall events. Hydroplaning tools are widely used by designers to reduce their roadway’s hydroplaning potential, therefore reducing the possibilities of severe crashes. This dissertation presents two methodologies for improving the prediction of hydroplaning potential. The first phase focused on improving an existing widely used software called PAVDRN. Using multiple datasets from the Florida Department of Transportation, the author filtered the data using specific criteria to leave only truly dynamic hydroplaning crashes. The author then evaluated PAVDRN’s prediction capabilities and assessed its reliability in predicting a hydroplaning crash. Using past accident statistics, the author accounted for extraneous factors that are difficult to capture, such as driver behavior, and obtained probability factors for a more realistic estimate of hydroplaning risk on roadways. The second phase focused on improving the modeling technique used in hydroplaning prediction tools. Currently when assessing a roadway’s hydroplaning potential, the roadside drainage is not considered in the analysis. The author modeled a combined pavement-drainage system using a 1D/2D method to better capture the effects of roadside drainage, especially in the events of flooding. The methodology used in modeling successfully captures the backwater effects that are caused under critical flooding conditions. Lastly the author created a new tool (MY-PAVDTCH) to provide design engineers with updated waterfilm thickness values under roadside drainage flooded conditions.